Diverticulitis – An Update from the Age Old Paradigm
Alexander T. Hawkins Paul E. Wise Tiffany Chan Janet T. Lee Tamara Glyn Mullaney Verity Wood Timothy Eglinton Frank Frizelle Adil Khan Jason Hall
For a disease process that affects so many, we continue to struggle to define optimal care for patients with diverticular disease. Part of this stems from the fact that diverticular disease requires different treatment strategies across the natural history- ...
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PubMed Central (PMC)
Curr Probl Surg. Author manuscript; available in PMC 2021 Oct 1.

Published in final edited form as:

PMCID: PMC7575828

NIHMSID: NIHMS1613333

PMID: 33077029

Diverticulitis – An Update from the Age Old Paradigm

, MD, MPH,1 ,2 ,2 ,3 ,4,5 ,6 ,4,5 ,4,5 ,7 ,7 ,8 ,8 ,8 ,9 ,10 ,10 ,11 ,12 ,13 ,13 ,14 ,15 ,16,17 ,16,17 and 10

Alexander T. Hawkins

1Section of Colon & Rectal Surgery, Department of Surgery, Vanderbilt University Medical Center, Nashville, TN.

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Paul E. Wise

2Section of Colon and Rectal Surgery, Department of Surgery, Washington University in St. Louis School of Medicine, St Louis, MO.

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Tiffany Chan

2Section of Colon and Rectal Surgery, Department of Surgery, Washington University in St. Louis School of Medicine, St Louis, MO.

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Janet T. Lee

3Division of Colon and Rectal Surgery, Department of Surgery, University of Minnesota, Saint Paul, MN.

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Tamara Glyn Mullaney

4Department of Surgery, University of Otago Christchurch, New Zealand.

5Department of Surgery, Canterbury District Health Board

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Verity Wood

6Department of Radiology, Canterbury District Health Board

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Timothy Eglinton

4Department of Surgery, University of Otago Christchurch, New Zealand.

5Department of Surgery, Canterbury District Health Board

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Frank Frizelle

4Department of Surgery, University of Otago Christchurch, New Zealand.

5Department of Surgery, Canterbury District Health Board

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Adil Khan

7Department of Surgery, Boston Medical Center, Boston, Massachusetts.

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Jason Hall

7Department of Surgery, Boston Medical Center, Boston, Massachusetts.

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M.I. Mohammed Ilyas

8Department of Surgery, University of Arizona, Tucson, AZ.

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Maria Michailidou

8Department of Surgery, University of Arizona, Tucson, AZ.

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Valentin N. Nfonsam

8Department of Surgery, University of Arizona, Tucson, AZ.

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Michelle Cowan

9Department of Surgery, University of Washington, Seattle, WA.

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Jennifer Williams

10Department of Colorectal Surgery, Digestive Disease and Surgery Institute, Cleveland Clinic, Cleveland, OH.

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Scott R. Steele

10Department of Colorectal Surgery, Digestive Disease and Surgery Institute, Cleveland Clinic, Cleveland, OH.

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Karim Alavi

11Division of Colorectal Surgery, University of Massachusetts Memorial Medical Center, Worcester, MA.

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C. Tyler Ellis

12Section of Colon & Rectal Surgery, Hiram C. Polk Jr. MD Department of Surgery, University of Louisville, Louisville, KY

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Danielle Collins

13St. Vincent’s University Hospital, Dublin, Ireland.

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Des C. Winter

13St. Vincent’s University Hospital, Dublin, Ireland.

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Karen Zaghiyan

14Cedars Sinai Medical Center, Los Angeles, CA.

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Gaetano Gallo

15Department of Medical and Surgical Sciences, University of Catanzaro, Catanzaro, Italy.

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Michele Carvello

16Humanitas Clinical and Research Center IRCCS, Colon and Rectal Surgery Unit, Rozzano (Milano), Italy.

17Humanitas University, Department of Biomedical Sciences, Pieve Emanuele (Milano), Italy.

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Antonino Spinelli

16Humanitas Clinical and Research Center IRCCS, Colon and Rectal Surgery Unit, Rozzano (Milano), Italy.

17Humanitas University, Department of Biomedical Sciences, Pieve Emanuele (Milano), Italy.

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Amy L. Lightner

10Department of Colorectal Surgery, Digestive Disease and Surgery Institute, Cleveland Clinic, Cleveland, OH.

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1Section of Colon & Rectal Surgery, Department of Surgery, Vanderbilt University Medical Center, Nashville, TN.

2Section of Colon and Rectal Surgery, Department of Surgery, Washington University in St. Louis School of Medicine, St Louis, MO.

3Division of Colon and Rectal Surgery, Department of Surgery, University of Minnesota, Saint Paul, MN.

4Department of Surgery, University of Otago Christchurch, New Zealand.

5Department of Surgery, Canterbury District Health Board

6Department of Radiology, Canterbury District Health Board

7Department of Surgery, Boston Medical Center, Boston, Massachusetts.

8Department of Surgery, University of Arizona, Tucson, AZ.

9Department of Surgery, University of Washington, Seattle, WA.

10Department of Colorectal Surgery, Digestive Disease and Surgery Institute, Cleveland Clinic, Cleveland, OH.

11Division of Colorectal Surgery, University of Massachusetts Memorial Medical Center, Worcester, MA.

12Section of Colon & Rectal Surgery, Hiram C. Polk Jr. MD Department of Surgery, University of Louisville, Louisville, KY

13St. Vincent’s University Hospital, Dublin, Ireland.

14Cedars Sinai Medical Center, Los Angeles, CA.

15Department of Medical and Surgical Sciences, University of Catanzaro, Catanzaro, Italy.

16Humanitas Clinical and Research Center IRCCS, Colon and Rectal Surgery Unit, Rozzano (Milano), Italy.

17Humanitas University, Department of Biomedical Sciences, Pieve Emanuele (Milano), Italy.

Correspondence: Alexander T Hawkins, MD, MPH, Section of Colon & Rectal Surgery, Vanderbilt University, 1161 21st Ave South, Room D5248 MCN, Nashville, TN 37232, Office: 615.343.4612, Fax: 615.343.4615, gro.cmuv@snikwah.xela

Monograph In Brief

For a disease process that affects so many, we continue to struggle to define optimal care for patients with diverticular disease. Part of this stems from the fact that diverticular disease requires different treatment strategies across the natural history- acute, chronic and recurrent.

To understand where we are currently, it is worth understanding how treatment of diverticular disease has evolved. Diverticular disease was rarely described in the literature prior to the 1900’s. In the late 1960’s and early 1970’s, Painter and Burkitt popularized the theory that diverticulosis is a disease of Western civilization based on the observation that diverticulosis was rare in rural Africa but common in economically developed countries. Previous surgical guidelines focused on early operative intervention to avoid potential complicated episodes of recurrent complicated diverticulitis (e.g., with free perforation) that might necessitate emergent surgery and stoma formation. More recent data has challenged prior concerns about decreasing effectiveness of medical management with repeat episodes and the notion that the natural history of diverticulitis is progressive. It has also permitted more accurate grading of the severity of disease and permitted less invasive management options to attempt conversion of urgent operations into the elective setting, or even avoid an operation altogether.

The role of diet in preventing diverticular disease has long been debated. A high fiber diet appears to decrease the likelihood of symptomatic diverticulitis. The myth of avoid eating nuts, corn, popcorn, and seeds to prevent episodes of diverticulitis has been debunked with modern data. Overall, the recommendations for “diverticulitis diets” mirror those made for overall healthy lifestyle – high fiber, with a focus on whole grains, fruits and vegetables.

Diverticulosis is one of the most common incidental findings on colonoscopy and the eighth most common outpatient diagnosis in the United States. Over 50% of people over the age of 60 and over 60% of people over age 80 have colonic diverticula. Of those with diverticulosis, the lifetime risk of developing diverticulitis is estimated at 10–25%, although more recent studies estimate a 5% rate of progression to diverticulitis. Diverticulitis accounts for an estimated 371,000 emergency department visits and 200,000 inpatient admissions per year with annual cost of 2.1–2.6 billion dollars per year in the United States. The estimated total medical expenditure (inpatient and outpatient) for diverticulosis and diverticulitis in 2015 was over 5.4 billion dollars. The incidence of diverticulitis is increasing.

Besides increasing age, other risk factors for diverticular disease include use of NSAIDS, aspirin, steroids, opioids, smoking and sedentary lifestyle. Diverticula most commonly occur along the mesenteric side of the antimesenteric taeniae resulting in parallel rows. These spots are thought to be relatively weak as this is the location where vasa recta penetrate the muscle to supply the mucosa. The exact mechanism that leads to diverticulitis from diverticulosis is not definitively known.

The most common presenting complaint is of left lower quadrant abdominal pain with symptoms of systemic unwellness including fever and malaise, however the presentation may vary widely. The gold standard cross-sectional imaging is multi-detector CT. It is minimally invasive and has sensitivity between 98% and specificity up to 99% for diagnosing acute diverticulitis. Uncomplicated acute diverticulitis may be safely managed as an out-patient in carefully selected patients. Hospitalization is usually necessary for patients with immunosuppression, intolerance to oral intake, signs of severe sepsis, lack of social support and increased comorbidities. The role of antibiotics has been questioned in a number of randomized controlled trials and it is likely that we will see more patients with uncomplicated disease treated with observation in the future

Acute diverticulitis can be further sub classified into complicated and uncomplicated presentations. Uncomplicated diverticulitis is characterized by inflammation limited to colonic wall and surrounding tissue. The management of uncomplicated diverticulitis is changing. Use of antibiotics has been questioned as it appears that antibiotic use can be avoided in select groups of patients. Surgical intervention appears to improve patient’s quality of life. The decision to proceed with surgery is recommended in an individualized manner.

Complicated diverticulitis is defined as diverticulitis associated with localized or generalized perforation, localized or distant abscess, fistula, stricture or obstruction. Abscesses can be treated with percutaneous drainage if the abscess is large enough. The optimal long-term strategy for patients who undergo successful non-operative management of their diverticular abscess remains controversial. There are clearly patients who would do well with an elective colectomy and a subset who could avoid an operation all together however, the challenge is appropriate risk-stratification and patient selection. Management of patients with perforation depends greatly on the presence of feculent or purulent peritonitis, the extent of contamination and hemodynamic status and associated comorbidities. Fistulas and strictures are almost always treated with segmental colectomy.

After an episode of acute diverticulitis, routine colonoscopy has been recommended by a number of societies to exclude the presence of colorectal cancer or presence of alternative diagnosis like ischemic colitis or inflammatory bowel disease for the clinical presentation. Endoscopic evaluation of the colon is normally delayed by about 6 weeks from the acute episode to reduce the risk associated with colonoscopy. Further study has questioned the need for endoscopic evaluation for every patient with acute diverticulitis. Colonoscopy should be routinely performed after complicated diverticulitis cases, when the clinical presentation is atypical or if there are any diagnostic ambiguity, or patient has other indications for colonoscopy like rectal bleeding or is above 50 years of age without recent colonoscopy.

For patients in whom elective colectomy is indicated, it is imperative to identify a wide range of modifiable patient co-morbidities. Every attempt should be made to improve a patient’s chance of successful surgery. This includes optimization of patient risk factors as well as tailoring the surgical approach and perioperative management. A positive outcome depends greatly on thoughtful attention to what makes a complicated patient “complicated”.

Operative management remains complex and depends on multiple factors including patient age, comorbidities, nutritional state, severity of disease, and surgeon preference and experience. Importantly, the status of surgery, elective versus urgent or emergent operation, is pivotal in decision-making, and treatment algorithms are divergent based on the acuteness of surgery. Resection of diseased bowel to healthy proximal colon and rectal margins remains a fundamental principle of treatment although the operative approach may vary.

For acute diverticulitis, a number of surgical approaches exist, including loop colostomy, sigmoidectomy with colostomy (Hartmann’s procedure) and sigmoidectomy with primary colorectal anastomosis. Overall, data suggest that primary anastomosis is preferable to a Hartman’s procedure in select patients with acute diverticulitis. Patients with hemodynamic instability, immunocompromised state, feculent peritonitis, severely edematous or ischemic bowel, or significant malnutrition are poor candidates. The decision to divert after colorectal anastomosis is at the discretion of the operating surgeon. Patient factors including severity of disease, tissue quality, and comorbidities should be considered. Technical considerations for elective cases include appropriate bowel preparation, the use of a laparoscopic approach, the decision to perform a primary anastomosis, and the selected use of ureteral stents.

Management of the patient with an end colostomy after a Hartmann’s procedure for acute diverticulitis can be a challenging clinical scenario. Between 20 – 50% of patients treated with sigmoid resection and an end colostomy after an initial severe bout of diverticulitis will never be reversed to their normal anatomy. The reasons for high rates of permanent colostomies are multifactorial. The debate on the best timing for a colostomy takedown continues. Six months is generally chosen as the safest time to proceed when adhesions may be at their softest allowing for a more favorable dissection. The surgical approach will be a personal decision by the operating surgeon based on his or her experience. Colostomy takedown operations are challenging surgeries. The surgeon should anticipate and appropriately plan for a long and difficult operation. The patient should undergo a full antibiotic bowel preparation. Preoperative planning is critical; review the initial operative note and defining the anatomy prior to reversal. When a complex abdominal wall closure is necessary, consider consultation with a hernia specialist. Open surgery is the preferred surgical approach for the majority of colostomy takedown operations. Finally, consider ureteral catheters, diverting loop ileostomy, and be prepared for all anastomotic options in advance.

Since its inception in the late 90’s, laparoscopic lavage has been recognized as a novel treatment modality in the management of complicated diverticulitis; specifically, Hinchey III (purulent) diverticulitis. Over the last decade, it has been the subject of several randomized controlled trials, retrospective studies, systematic reviews as well as cost-efficiency analyses. Despite being the subject of much debate and controversy, there is a clear role for laparoscopic lavage in the management of acute diverticulitis with the caveat that patient selection is key.

Segmental colitis associated with diverticulitis (SCAD) is an inflammatory condition affecting the colon in segments that are also affected by diverticulosis, namely, the sigmoid colon. While SCAD is considered a separate clinical entity, it is frequently confused with diverticulitis or inflammatory bowel disease (IBD). SCAD affects approximately 1.4% of the general population and 1.15 to 11.4% of those with diverticulosis and most commonly affects those in their 6th decade of life. The exact pathogenesis of SCAD is unknown, but proposed mechanisms include mucosal redundancy and prolapse occurring in diverticular segments, fecal stasis, and localized ischemia. Most case of SCAD resolve with a high-fiber diet and antibiotics, with salicylates reserved for more severe cases. Relapse is uncommon and immunosuppression with steroids is rarely needed. A relapsing clinical course may suggest a diagnosis of IBD and treatment as such should be initiated. Surgery is extremely uncommon and reserved for severe refractory disease.

While sigmoid colon involvement is considered the most common site of colonic diverticulitis in Western countries, diverticular disease can be problematic in other areas of the colon. In Asian countries, right-sided diverticulitis outnumbers the left. This difference seems to be secondary to dietary and genetic factors. Differential diagnosis might be difficult because of similarity with appendicitis. However accurate imaging studies allow a precise preoperative diagnosis and management planning. Transverse colonic diverticulitis is very rare accounting for less than 1% of colonic diverticulitis with a perforation rate that has been estimated to be even more rare. Rectal diverticula are mostly asymptomatic and diagnosed incidentally in the majority of patients and rarely require treatment. Giant colonic diverticula (GCD) is a rare presentation of diverticular disease of the colon and it is defined as an air-filled cystic diverticulum larger than 4 cm in diameter. The pathogenesis of GCD is not well defined.

Overall, the management of diverticular disease depends greatly on patient, disease and surgeon factors. Only by tailoring treatment to the patient in front of us can we achieve optimal outcomes.

Introduction

Regardless of how the problem is examined, diverticular disease is a significant burden both patients and health care systems. In Western and industrialized nations, diverticulosis of the sigmoid colon, defined by the sac-like protrusion of the colonic wall, has prevalence rates between 5 and 45%, depending on the age and method of diagnosis. 1 Approximately 4 to 15% of patients with diverticulosis develop diverticulitis. 2–4 Complications lead to substantial morbidity and mortality. For perforation alone, the 1-year mortality is 19%. 5 In 2004, diverticular disease was responsible for 313,000 hospitalizations, 1.9 million ambulatory care visits, and 3365 deaths in the United States. 6 Spending on diverticular disease in the United States has been estimated at 2.5 billion dollars per year. 7 In 2004, there were an estimated 2.8 million prescriptions at a cost of $100 million filled at retail pharmacies for diagnosis of diverticular disease. 6 Between 1998 and 2005, US hospital admissions for diverticulitis increased by 26% and elective operations by 29%. 8

An attempt to capture the entire spectrum of management of diverticular disease is an ambitious one. A disease process that spans both the acute and chronic, the mild and severe and the young and the old is difficult to define in a single reading. But in this paper, we lay the foundation for the management of the breath of diverticular disease. Decades of research inform our current best practices. Details on these follows below.

Diverticulitis: a historical perspective

Introduction

The precise underlying etiologies of diverticular disease, risk factors for acute episodes, and diets that may prevent disease occurrence have long been the subject of debate. Diverticular disease was rarely described in the literature prior to the 1900’s. In the late 1960’s and early 1970’s, Painter and Burkitt popularized the theory that diverticulosis is a disease of Western civilization based on the observation that diverticulosis was rare in rural Africa but common in economically developed countries, 9,10 though critics will note that in their original paper they assessed neither diet nor presence of diverticulosis to support this claim. Their subsequent studies on colonic pressure, 11 stool weight, and colonic transit times 12 to substantiate their hypotheses have also been challenged.

The first description of surgical management of diverticulitis was by Mayo, who outlined the operations and pathologic findings for a series of five patients in 1907. 13 In his initial papers, Mayo also briefly outlined surgical options for diverticulitis including abscess drainage, and staged operations such as diverting colostomy with or without subsequent resection and eventual colostomy closure. 14 This was followed by the three-stage operation proposed by Rankin and Brown 15, which subsequently has been superseded by the two-stage operation eponymous with Henri Hartmann, who first proposed the procedure in 1921 for the management of sigmoid carcinoma. 16

The evolution in our understanding of the natural history of diverticulitis has altered medical and surgical management recommendations over the course of the last 50 years. Despite the debunking of old surgical dogma, modern perspectives have yet to completely translate to the realm of public knowledge. In this section common myths and misconceptions will be discussed.

Diverticulitis: when to cut it out?

Previous surgical guidelines focused on early operative intervention to avoid potential complicated episodes of recurrent complicated diverticulitis (e.g., with free perforation) that might necessitate emergent surgery and stoma formation. This included recommendations for routine elective resection after two attacks in patients over 50 years of age and after one attack in patients younger than 50 years of age. The premise of these recommendations had underlying assumptions that include the following: 1) patients who had already experienced more than one prior episode would be less responsive to medical therapy, lead to complicated diverticulitis, need for emergent operation/stoma, and thus have a higher mortality risk, and 2) young patients would have a longer potential time to experience a recurrence and its associated sequelae.

How many episodes is too many episodes?

In the late 1960’s, Parks found that in a cohort of 455 patients admitted for treatment of diverticulitis, 317 were treated medically on the first admission. Patients included in this series had clinical and radiologic evidence of diverticulitis on barium enema and/or evidence of local diverticular inflammation at the time of operation or necropsy. Of patients treated medically, 24.6% (78 patients) were subsequently readmitted with a second attack, 3.8% with a third attack, and 1.6% with a fourth attack. Of these recurrent episodes, 46% occurred within the first year. Because 20 of the 78 patients (25.6%) with recurrent attacks ultimately needed surgery, and the mortality rate associated with the second attack was 7.7% compared to only 3% in the first attack, Parks concluded that medical treatment of repeat episodes was less likely to be successful. 17 This observation formed some of the basis for recommending early surgery after one or two episodes to prevent future attacks.

As of the 1990’s, both the American Society of Colon and Rectal Surgery 18 as well as the European Association for Endoscopic Surgery 19 supported the recommendation for elective resection after two episodes of uncomplicated diverticulitis. However, criticism of this recommendation began to build as newer studies challenged dogma founded on the limited data from more than 20 years prior. “Modern” series have been published in the era of more advanced diagnostic imaging usually with computed tomography (CT) scanning, routine use of image-guided percutaneous drainage, and advances in the medical management of sepsis. This more recent data has challenged prior concerns about decreasing effectiveness of medical management with repeat episodes and the notion that the natural history of diverticulitis is progressive. It has also permitted more accurate grading of the severity of disease and permitted less invasive management options to attempt conversion of urgent operations into the elective setting, or even avoid an operation altogether.

The role of “early surgery” to prevent future complicated diverticulitis

Contrary to prior dogma, complicated diverticulitis appears to present more commonly in patients who had only had one or two attacks, 20 and patients with more than two episodes were not at increased risk for poor outcomes. In other words, patients who had experienced more than two episodes were actually less likely to experience free perforation, had a lower rate of requiring diverting ostomy, and higher rates of successful resection with primary anastomosis. 21 Therefore, in the absence of feculent peritonitis, when patient physiology, comorbidities, and local technical expertise permits, non-operative management of perforated diverticulitis presenting with abscess or even locules of free air has been demonstrated to be highly successful and feasible in the majority of patients. 22

The decision to offer surgery for other manifestations of complicated diverticulitis such as free perforation, fistula, or obstruction, is generally straightforward. However, some debate still remains about what to do with the diseased colonic segment following resolution of an episode of complicated diverticulitis with abscess treated with or without percutaneous drainage. Data that supports the recommendation for elective colectomy after diverticulitis with abscess is based on concerns that recurrence rates can be as high as 40%. 23,24 A recent review of a statewide database in New York suggests that many patients could be successfully managed non-operatively without routine colectomy after their first presentation of diverticular abscess. Based on more than 10,000 admissions for initial diverticular abscess, observation without elective colectomy was associated with lower stoma rates, fewer inpatient hospital days, but higher costs. Of this cohort, 31% failed initial non-operative management, 16% underwent elective colectomy within 6 months of discharge, and 52% of patients continued with nonoperative management. In this latter group, overall recurrence at 5 years was 25% (and only 13% if the patients made it beyond 1 year without recurrence).

Role of routine elective resection for young patients

Routine elective resection based on age <50 is no longer recommended. More recent studies have allayed concerns that diverticulitis is more virulent in younger patients, 25 and therefore routine resections are no longer recommended to prevent the possibility of recurrence requiring emergency colectomy and/or colostomy. However, in a large statewide database study by Anaya and Flum in 2005 that included more than 20,000 patients treated without initial operation, the overall recurrence rate was 19%, but the rate was 27% in patients under 50 years of age versus 17% in those over 50 (p<0.001). While the overall rate of emergency colectomy or colostomy was only 5.5%, it was also significantly more common in younger patients (7.5 vs. 5.0%, p<0.001). 20 However, a contemporary study in 2004 by Guzzo and Hyman demonstrated that the risk of requiring surgery at the initial admission was similar between older (22%) and younger patients (24%, p=0.8). There was a low rate of recurrence following successful medical management, with perforation risk of only 0.5%, suggesting that the role of performing routine resection in young patients to prevent emergent colectomy in the future may not be warranted. 26 While virulence appears the same across age groups, the potentially longer time course over which disease can recur should still be taken into consideration when discussing surgery with young patients.

Cost-benefit modeling has been performed in both patients over and under 50 years of age, and also speak against the prior recommendation to routinely offer resections to young patients. One study utilizing Markov modeling of elective resections after two episodes versus medical therapy show lower quality adjusted life years associated with routine resection after two episodes. 27 When similar modeling was performed looking at deferring elective colectomy until after a fourth attack, the finding was that expectant management was the dominant strategy in both young (age 35) and older (age 50) hypothetical cohorts. Notably, a very small proportion (0.3%) of patients would actually develop a fourth attack of diverticulitis. Deferring surgery until the fourth episode in patients over 50 resulted in only a marginal decrease in mortality of 0.5%, 0.7% fewer colostomies, and cost savings of approximately US $1000 compared to colectomy after the first episode. 28 Similarly in younger patients, colectomy after the fourth episode resulted in 0.1% fewer deaths, 2% fewer colostomies, and cost savings of US $5429 per patient.

Overall, the practice of recommending elective colectomy to prevent future recurrence (regardless of age) out of the fear of need for emergency surgery and associated stoma formation is generally discouraged as the available data does not support this practice. The estimated rate of requiring urgent Hartmann’s procedure is 1 in 2000 patient-years of follow up. 29 Given that elective surgery carries its own set of complications and risks, more recent evidence has therefore led to a modification in the ASCRS guidelines stating that the “…decision to recommend elective sigmoid colectomy…should be individualized”, depending on the medical condition of the patient, frequency and severity of attacks, and persistence of symptoms. 30

Let food be thy medicine—fiber, seeds, nuts, and other diverticular diet lore

The role of diet in preventing diverticular disease has long been debated. Even 40 years ago, there was some postulation that high fiber diets may actually reduce the incidence of diverticular disease. This has been supported by observational studies noting that populations that adopted more “Western” diets with refined grains and decreased fiber had higher rates of diverticular disease. 10,12 Specifically, researchers have tried to establish the relationship between high fiber diets and the development of diverticulosis, the role of specific foods such as nuts and seeds in the precipitation of diverticulitis, and the role of specific diets in the management and treatment of diverticulitis during an acute episode.

Fiber – an ounce of prevention?

The Dietary Guidelines for Americans (2015–2020) recommends a dietary fiber intake of 14 grams per 1,000 calories consumed. For example, for a 2,000-calorie diet, the fiber recommendation is 28 grams per day. 31 However, it is difficult to find the originating source for these recommendations. The exact role that fiber plays in the pathogenesis of asymptomatic and symptomatic diverticular disease is still a subject of debate. While population-based studies such as the Million Women Study (MWS) 32 and the European Prospective Investigation into Cancer and Nutrition (EPIC) 33 suggest that a high fiber diet protects against diverticula becoming symptomatic, cross-sectional studies looking at asymptomatic diverticula identified on colonoscopy did not demonstrate that lower fiber diets or constipation were risk factors for developing diverticulosis 34 and did not identify a protective role of a high fiber diet. 1 It is possible that the reason for this conflicting evidence is due to study design and the variation in endpoints measured. Interestingly, there are no studies that clearly address whether fiber supplements (as opposed to dietary fiber) reduces the risk of diverticulitis attacks. 35 However, as many people find it difficult to obtain the recommended intake of fiber through diet alone, supplementation is a low-risk method of increasing intake. On balance, given that a high fiber diet appears to decrease the likelihood of symptomatic diverticulitis, and may confer other health benefits beyond the management of diverticular disease, the recommendation is for patients to adhere to a high fiber diet.

Fiber intake and diverticular disease

Multiple prospective, population-based studies have looked at aspects of diets and their association with diverticular disease. Supporting the comments above, the MWS, based out of the UK, surveyed 1.3 million women aged 50–65 years regarding social, demographic, and lifestyle factors and were then linked to hospital records to confirm rates of symptomatic diverticular disease. 32 This study demonstrated that high intake of dietary fiber was associated with a reduced risk of diverticular disease. Particularly, a diet high in fruit and cereals was most protective. The relative risk of diverticular disease per 5 g/day of fiber intake was 0.86 (95% CI, 0.84–0.88). The mean total intake of dietary fiber was 13.8 grams per day, which is still less than half the current recommended daily intake of 25–30 grams per day.

Similarly, the EPIC-Oxford study examined the association between fiber intake and admission to hospital or death from diverticular disease in more than 47,000 people over an average period of 11.6 years. Participants in the highest quintile of fiber intake (≥25.5 g/day for women and ≥26.1 g/day for men) had a lower relative risk (0.59, 95% CI 0.46–0.78, P<0.001) of both complicated and uncomplicated diverticular disease compared with those in the lowest quintile (<14 g/day for both women and men). Vegetarians made up 33% of the subjects and demonstrated an additional 31% lower risk of diverticular disease compared to meat eaters. 36

Nuts, seeds, and diverticulitis

Patients with diverticular disease commonly ask whether they should avoid eating nuts, corn, popcorn, and seeds to prevent episodes of diverticulitis. The rationale for this was that these substances tend to pass through the gastrointestinal tract almost intact and would therefore be of the perfect shape and size for getting lodged in a diverticulum, presumably resulting in diverticulitis. 37 In reality, the precise mechanism for precipitating diverticulitis is likely more complex and still not completely understood. While this recommendation seems to make theoretical sense, this dietary urban legend has essentially been debunked. 38 In the Health Professionals Follow-up Study (HPFS), a cohort of more than 47,000 men were surveyed regarding food intake frequency. There was actually an inverse association between nut and popcorn assumption and risk of diverticulitis, defined as abdominal pain and one of the following: 1) fistula, abscess, perforation, or obstruction; 2) treatment with antibiotics, hospitalization, or surgery; or 3) severe or acute or presenting with fever, requiring medication, or evaluated with CT scan. Self-reports of these symptoms were then corroborated with medical records. Men who ate these foods at least twice per week were actually less likely to develop diverticulitis, even when controlling for other potential risk factors including age; body mass index; dietary fat, fiber, and red meat consumption; physical activity; cigarette smoking; and NSAID and acetaminophen use. There was no association between the development of diverticular bleeding or uncomplicated diverticulosis. In particular, insoluble fiber or cellulose appeared to have the strongest protective effect. 39

Low fiber/low residue diets and acute diverticulitis

Traditionally, many caregivers have advocated for a low residue diet during an acute episode of diverticulitis once a liquid diet has been tolerated without pain or alteration in clinical status. The term “low residue” diet has fallen out of favor as the term is non-specific and difficult to quantify. 40 Instead, the suggested terminology is a “low fiber” diet, generally defined as <10 g/day. 41,42 Currently in the literature the terms low residue and low fiber may be used interchangeably, however. Conceptually, this dogma of low fiber diets with diverticulitis would be based on a low fiber diet theoretically reducing the frequency and volume of stools to ease passage through the inflamed segment allowing the inflammation to improve more quickly. Once the acute episode has resolved, the general recommendation, as described above, would be to then gradually resume a high fiber diet to minimize further attacks. However, the evidence for adhering to a low fiber diet during an acute episode is based on scant evidence, 43 so this dogma remains without scientific evidence.

Summary

Overall, the recommendations for “diverticulitis diets” mirror those made for overall healthy lifestyle – high fiber, with a focus on whole grains, fruits and vegetables. Many people who develop asymptomatic diverticulosis will not develop diverticulitis and its potential associated sequelae. In those who do develop symptoms, the attitude towards early surgical management is shifting to more expectant management with delay of definitive surgery. Furthermore, the focus of surgical decision-making is moving away from dogmatic recommendations in favor of shared decision-making between patient and surgeon, balancing severity of symptoms, patient lifestyle, age, and morbidity.

Epidemiology/Classification/Pathophysiology of Diverticulitis - Janet Lee

Epidemiology

Diverticulosis is one of the most common incidental findings on colonoscopy 6 and the eighth most common outpatient diagnosis in the United States. 44 Over 50% of people over the age of 60 and over 60% of people over age 80 have colonic diverticula. 44,45 Of those with diverticulosis, the lifetime risk of developing diverticulitis is estimated at 10–25%, 46 although more recent studies estimate a 5% rate of progression to diverticulitis. 2 Diverticulitis accounts for an estimated 371,000 emergency department visits and 200,000 inpatient admissions per year with annual cost of 2.1–2.6 billion dollars per year in the United States. 44,47 The estimated total medical expenditure (inpatient and outpatient) for diverticulosis and diverticulitis in 2015 was over 5.4 billion dollars. 47

Painter and Burkitt first observed that diverticulosis is more common in urbanized/industrialized areas than rural Africa. 10 The paucity of fiber in the Western diet has been linked to higher rates of diverticulosis. A low fiber diet results in less stool volume, decreased colon diameter, increased intraluminal pressure and increased formation of diverticula. Increased industrialization and urbanization and greater spread of the Western diet have led to higher rates of diverticular disease in other parts of the world such as Asia and Africa. 48,49 White people have the highest prevalence of hospitalization for diverticulitis (62/100,000) versus African Americans or Hispanics (30/100,000) and Asians (10/100,000). 50 In large database studies of diverticulitis, Whites comprise 60–70% of hospitalized patients with diverticulitis. 8 In Asian countries, diverticulitis is much less common that in Western countries, but when it does occur, it more frequently affects the right side of the colon. If Asian patients move to Westernized areas, however, the risk of diverticular disease and left sided disease increases. Autopsy studies have shown a 1% prevalence of diverticulosis in Japanese who live in Japan, but a 50% prevalence of Japanese living in the United States. 51

The incidence of diverticulitis is increasing. Wheat and Strate 50 performed a retrospective review of the Nationwide Inpatient Sample from 2000 through 2010 analyzing trends in hospitalization for diverticulitis and diverticular bleeding. Over the 10-year study period there were over 2.1 million hospitalizations for diverticulitis with an average of 195,000 per year. The number of admissions for diverticular bleeding decreased over the study period while admissions for diverticulitis increased over the 10 years, with a peak in 2008. 50

Lee et al52 also performed a retrospective review to identify trends in diverticulitis. Using data from the Rochester Epidemiology Project, they looked at changes in demographics of patients between 1980 and 2007 who developed diverticulitis. They found a significant increase in incidence of diverticulitis between decades (1980–1989 vs. 1990–1999 vs. 2000–2007, p<0.001). The authors estimate an increase of 50% between 1990–1999 and 2000–2007. The authors also found that visceral and subcutaneous adipose tissue were independently associated with diverticulitis, suggesting that distribution of body weight and fat (ie central obesity) was more closely responsible for increasing rates of diverticulitis. 52

Diverticular disease is more common in middle-aged to older individuals, and its prevalence increases with age as well. By age 40, 5% of the population has diverticulosis, while the prevalence may be as high as 60–80% by age 80. Recent studies have shown that rates of diverticulitis in young people is increasing as well. Bharucha et al 53 found that individuals aged 40–49 have had a 132% increase in incidence from 1980 through 2007. Etzioni et al 8 also performed a retrospective review of the changing demographics of patients hospitalized for diverticulitis between 1998 and 2005. Among patients aged 18–44, the rates of admission for diverticulitis increased by 82% and number of elective operations increased by 73% over the study period. In contrast, rates of admission for diverticulitis in the 65–74 year-old group remained stable, and rates of admission for diverticulitis decreased in the 75+ year old group. 8

In younger age groups, diverticular disease is more common in men than women, with an estimated 2–3:1 ratio. After the 6th decade, however, the prevalence is more similar. 50,53 Women make up a higher proportion of hospitalized diverticulitis patients 8,50 and have a higher incidence of fistula formation. Men are more likely to have bleeding from diverticular disease.

Other risk factors for diverticular disease include use of NSAIDS, aspirin, steroids, opioids, smoking and sedentary lifestyle. Family history and genetics is also an important risk factor for development of diverticulitis. Twin studies have shown that the odds of developing diverticular disease if a co-twin has the disease is much higher in monozygotic twins than dizygotic twins. 54,55 Using statistical modeling, studies have shown that genetics accounts for 40–50% of risk for diverticular disease while environmental effects account for 50–60% of the trait variability. 54,55

Classification

Diverticulitis may be classified as either uncomplicated or complicated. The vast majority of patients will have uncomplicated diverticulitis (~90%) with a typical presentation of fever, abdominal pain and/or leukocytosis. Complicated diverticulitis may present with abscess, fistula, perforation, stricture, or peritonitis. Abscess (70%) is the most common manifestation of complicated diverticulitis. 53

Diverticulitis can also be classified as acute or chronic. Chronic diverticulitis can present as recurring, intermittent episodes of acute disease, or persistent, symptomatic inflammation; so-called smoldering diverticulitis. The 10-year risk of recurrence of diverticulitis is 20% after one episode. After 2 episodes of diverticulitis, the 1-year risk is 20%. Hall et al 56 performed a retrospective review of all diverticulitis patients over a 6-year period with a CT-documented episode of diverticulitis and analyzed risk factors for recurrence. In this study of 672 patients, the mean follow-up was 42.8 +/− 24 months. The vast majority of patients had uncomplicated diverticulitis while 8.9% presented with complicated disease. The overall recurrence rate at 5 years was 36%. Complicated recurrence was 3.9%. Risk factors for recurrent diverticulitis included irritable bowel syndrome, complicated presentation, previous hysterectomy, and family history of diverticulitis. Family history, length of involved colon and retroperitoneal abscess were independently statistically significant risk factors for recurrent disease. 56

Other newer terms have been used to classify diverticular disease including segmental colitis associated with diverticulosis (SCAD) and symptomatic uncomplicated diverticular disease (SUDD) 57,58 ( ). SCAD is different than diverticulitis in that a nonspecific inflammation of the colon is seen in an area of diverticula, but the diverticular orifice itself is not involved. 59 SCAD is typically benign and self-limited. It may present with rectal bleeding, diarrhea or abdominal pain. Histologically and endoscopically, SCAD may resemble inflammatory bowel disease. SUDD is characterized by chronic abdominal pain in absence of acute symptoms, radiographic evidence, or endoscopic evidence of diverticulitis or colitis. 58 SUDD is similar to irritable bowel syndrome as both involve visceral hypersensitivity and changes in colonic motility. 60

Table 2b.

ClassCT FindingsStage 0Mild clinical diverticulitisStage IaConfined pericolic inflammation/phlegmonStage IbConfined pericolic abscess (within sigmoid mesocolon)Stage IIPelvic, distant intra-abdominal or intraperitoneal abscessStage IIIGeneralized purulent peritonitisStage IVFecal peritonitis

The most well-known classification schema for acute diverticulitis is the Hinchey criteria ( ). First described by Hinchey et al in 1978, the Hinchey criteria classify the disease based on extent of inflammatory complications. 61 These classification schema help identify patients that are more likely to have recurrent attacks or require surgical intervention after the initial presentation of diverticulitis. Ambrosetti 23 developed radiologic criteria to help guide clinical management based on CT findings ( ). Using this criteria, moderate diverticulitis is defined by localized wall thickening and inflammation of pericolic fat. Severe diverticulitis is defined by wall thickening as well as inflammation, abscess, extraluminal air or contrast. The modified Hinchey classification ( ) has been applied to preoperative CT findings as well to help guide management. 62 The modified Hinchey criteria correlates with postoperative morbidity and mortality and is also predictive of recurrence when managed nonoperatively. 24 The Hinchey classification, however, is limited, however, as the presence of purulent or feculent peritonitis can only be determined at the time of surgery.

Table 1:

ClassCT FindingsStage ILocalized abscess (pericolic abscess/phlegmon)Stage IIPelvic intraabdominal or retroperitoneal abscessStage IIIGeneralized purulent peritonitisStage IVGeneralized feculent peritonitis

Table 2:

ClassCT findingsModerate diseaseLocalized sigmoid wall thickening (<5mm)

Pericolic fat strandingSevere diseaseAbscess

Extraluminal air

Extraluminal contrast

Pathophysiology

Diverticula most commonly occur along the mesenteric side of the antimesenteric taeniae resulting in parallel rows. These spots are thought to be relatively weak as this is the location where vasa recta penetrate the muscle to supply the mucosa. Colon diverticula are false diverticula and contain only mucosal and muscularis mucosal layers. The reason behind their formation is unclear with the most common theories involving structural abnormalities of the colon wall, disordered motility and fiber deficiencies. Studies have shown thickening of the circular muscle, shortening of the taenia, and narrowing of the lumen in patients with diverticular disease compared with those with normal colons. 63 The thickened circular muscle in patient with diverticular disease is the result of increased elastin deposition as opposed to muscular hypertrophy or hyperplasia, with over 200% increase of elastin in patients compared with controls. 64 Studies have also shown that patients with diverticular disease have greater rates of collagen cross-linking. 65 Increased collagen cross-linking may cause the tissues to become stiffer leading to a loss in compliance of the colonic submucosa, making it more susceptible to injury. Collagen cross-linking increases with age, and thus, may explain why the prevalence of diverticular disease increases with age. Changes in collagen cross-linking and elastin deposition may also explain why patients with connective tissue disorders are also more prone to diverticulosis earlier in life.

In addition to changes in structure and composition of colonic tissue, patients with diverticulosis also have higher intraluminal pressures in the sigmoid colon versus controls. 66 This can lead to increased risk of injury to the mucosa with high intraluminal pressures. Studies have also shown that patients with diverticular disease have disordered colonic motility in the descending and sigmoid colon with disorganized, frequent retrograde propagation of propulsions. 60 In a high fiber diet, motility is faster and intraluminal pressures are lower, which may explain why a high fiber diet is protective against diverticular disease.

The exact mechanism that leads to diverticulitis from diverticulosis is not definitively known. Diverticulitis is commonly believed to be caused by obstruction of a diverticulum, leading to stasis, ischemia, microperforation and infection. 67 The microperforation then leads to a characteristic inflammatory response of varying degrees. Development of an abscess, phlegmon, fistula or free perforation may then follow. Inflammation in the surrounding tissues can then lead to altered gut function and change in bowel function.

More recent studies suggest other potential contributing factors including chronic inflammation, the gut microbiome, and genetics. 54,55,68–72 Risk factors for other known chronic inflammatory diseases such as cardiovascular disease and diabetes are also risk factors for diverticulitis. Increased dietary fiber may be protective against diverticulitis by altering the microbiome. Patients with diverticular disease have a different composition in the intestinal microbiome than controls, with higher levels of Bifidobacterium. 71 Other studies have found differences in composition of patients with active diverticulitis compared with controls with diverticulosis. 69,70 The correlation or causation these potential contributors to the development of diverticulitis is unknown.

Schafmayer et al 72 recently performed a genome-wide association study looking at genetic risk factors for diverticulosis and diverticulitis. Using genotypes from a large Biobank of patients of European descent, they compared loci of cases and controls. They found that candidate genes in case with diverticulosis were related to intestinal neuromuscular function and impaired connective fiber support. Identified candidate genes for cases with diverticulitis were related to epithelial dysfunction. This study suggests a genome-specific reason for the development of diverticular disease and diverticulitis and may help identify those at higher risk of developing symptoms or complications

Summary

The incidence of diverticulitis is increasing, and the age of the average patient is decreasing. The change in the Western diet, inflammation, and perhaps gut microbiome may have some relation to the evolution of the disease. Understanding the exact mechanism of diverticular formation or transformation from diverticulosis to diverticulitis may help guide future disease prevention and treatments.

Presentation, Preferred Imaging and Criteria for Outpatient Management

Introduction

The epidemiology of diverticular disease has been evolving over the past century. 73 Currently, 70% of patients over the age of 80 years have diverticulosis, and there is an increasing incidence of younger patients with symptomatic disease. 74 Findings from screening colonoscopy suggest a progressive disorder, supported by the increased prevalence and density of diverticula with age. 75 Of those with diverticular disease, recent studies suggest 3–7% may develop acute diverticulitis (AD). 2,76

National database studies suggest a continuing increase in emergency presentations for AD and the associated costs over the past two decades.73,74,77,78 The aging population may explain some of this, however an exponential rise in the prevalence in younger age categories and other demographic groups (specifically women) have also been implicated.

In the western population diverticulosis is predominantly left sided (86%), particularly affecting the sigmoid colon, with the right side or whole colon less commonly affected, and symptomatic disease also following this distribution. 75 In Asian communities however right sided disease predominates, and may be confused with appendicitis. Acute diverticulitis may be defined as uncomplicated or complicated (approximately 15–35% of presentations) in the presence of perforation, abscess, fistulisation or obstruction. 79–81 The vast majority (>80%) of acute presentations with AD are now managed non-operatively. 77,82

Presentation

The most common presenting complaint is of left lower quadrant abdominal pain with symptoms of systemic unwellness including fever and malaise, however the presentation may vary widely. The differential diagnosis is broad and includes appendicitis and malignancy (among others). Initial assessment aims to establish the diagnosis of AD, the presence of (or risk of developing) complications and the best course of treatment.

A routine history should focus on duration and details of illness and risk factors for malignancy or other differential diagnoses. Clinical examination should establish the presence and degree of sepsis and the presence and extent of peritonism. Standard laboratory testing includes a complete blood count, urea, electrolytes and inflammatory markers, looking for evidence of inflammatory response and effect on other organ systems. 30,83 However, normal laboratory testing does not preclude a diagnosis of AD. 84 Clinical assessment in conjunction with laboratory testing can be reasonably accurate, 85 however there is considerable overlap of symptoms with other diseases 29and as such radiologic investigation is essential for an accurate diagnosis.

Preferred Imaging

Plain Film

Plain radiography of the abdomen may demonstrate gross free air or obstruction, however it lacks sensitivity and specificity and therefore does not have a routine role in the evaluation of AD. 86 A plain radiograph of the chest may be diagnostically useful if the differential diagnosis includes pneumonia or as part of the peri-operative work-up if surgery is deemed necessary.

Contrast Enema

The initial investigation of choice prior to the advent of computed tomography (CT) was contrast enema. While many earlier studies linked the presence of left iliac fossa symptoms and subsequent barium enema showing diverticulosis as evidence the patient had diverticulitis, subsequent reviews cast doubt on the reliability of this assumption. 29

Barium enema is not often used in the acute situation as barium can cause peritonitis and obscure views if a subsequent CT is required. Water soluble contrast has been used as an adjunct to primitive CT, 87 however it is not now commonly used to diagnose AD as it has been surpassed in sensitivity and speed by the latest iterations of CT technology.

Contrast enema gives good luminal images but does not reflect the peri-colonic process. It may have a role in the identification and anatomic mapping of structuring or fistulous disease, however this has largely been surpassed by the use of CT with rectal contrast. 88

Ultrasound

Ultrasound (US) has been proposed as an alternative or adjunctive imaging modality without the potential harm of radiation exposure. 89,90 Proponents advocate a role in diagnosis and monitoring of uncomplicated diverticulitis 89 and possibly in intervention for complicated disease. The German guidelines recommend a ‘Qualified abdominal US’ as the first line imaging investigation for uncomplicated AD. 86 The defining features of AD on US depend on the stage of the disease and include colonic wall thickening and peri-diverticular inflammation appearing as non-compressible, hyperechoic fat which is tender to probe pressure. 89,90 Complicated disease such as abscesses may be demonstrated on US and this used to guide drainage.

Ultrasound is user dependent, has a tendency to underestimate the stage of the disease and sensitivity may depend on the location of the disease (for example deep mesenteric and pelvic disease is better imaged by CT) and patient body habitus. In experienced hands using a targeted approach, sensitivity and specificity approach 98%. 86 A meta-analysis found it comparable to CT in the accuracy of diagnosis of AD, however it is less likely to identify other sources of pathology. 91 It may be used as alternative initial investigation to CT in patients in which a CT may be contraindicated (for instance pregnancy). 30

While in some parts of Europe US has gained acceptance as first line of investigation, this is in contrast to the general situation in most of the western world, where CT has become the preferred technique.

Computed Tomography

The gold standard cross-sectional imaging is multi-detector CT. It is minimally invasive and has sensitivity between 98% and specificity up to 99% for diagnosing AD. 23,30,92,93 In the absence of contra-indications, intravenous contrast is typically used. In addition, oral or rectal water-soluble contrast can be added as adjuncts to enhance sensitivity and specificity depending on the clinical scenario. Multiple phases (including non-contrast and portal venous) are recorded.

Typical CT findings include the presence of diverticula, segmental, symmetrical wall thickening, hyper-enhancement and pericolic inflammation. In complicated disease, abscesses, localised or free intra-peritoneal gas, fistulisation or evidence of obstruction may be seen. 94

Computed tomography has a role in confirming the diagnosis, but also predicting failure of non-operative management; extra-colonic contrast and distant free intraperitoneal gas are associated with the need for surgery. 95,96 In order to enable more standardised reporting and prognostication, numerous classification systems have been proposed. The most recent is a modification of the previously described Hinchey classification of operative findings, 61 in which AD is classified as ‘Uncomplicated’ or ‘Complicated’, and the latter subdivided from pericolic air through to diffuse fluid and distant free air depending on the degree of radiologic evidence of contamination (see ). 93 The authors proposed an algorithm for management based on a combination of the radiologic and clinical features of the individual case.

One of the concerns in the liberal use of CT, particularly in the increasing younger cohort of AD patients, is radiation dose. Walter et al have shown that lowering the dose of radiation by 50% may still provide sufficient diagnostic accuracy. 97

Magnetic Resonance Imaging

Magnetic resonance imaging (MRI) is a radiation free alternative to CT (where CT is contraindicated) and provides good sensitivity and specificity (up to 94 and 92% respectively).88 It is less user-dependent than US and may be more sensitive and specific than US in patients with a higher body mass index or where another pathology is possible or suspected. 30

Criteria for Outpatient Management

Historically acute diverticulitis has been managed in a hospital setting with intravenous antibiotics and ‘gut rest’. Increasingly, this paradigm has been challenged and the value of antibiotics and hospitalisation questioned. The combination of an aging population and the increased prevalence of diverticular disease will drive an increase in presentations of AD and put pressure on limited in-patient systems. Hospital admission may be necessary for treatment or monitoring purposes however, early risk stratification can now be performed with a combination of clinical, laboratory and radiologic assessment and a decision made on the safety of out-patient management or the need for intervention.

Summary of Evidence on Outpatient Management

There has been increasing interest in the out-patient management of AD over the past 2 decades. The majority of data comes from prospective and retrospective cohort studies, however there is also one randomised controlled trial. 98 The DIVER Trial was a prospective, multicentre randomised clinical trial (RCT) which compared hospitalisation and out-patient management in terms of treatment failure, the subsequent need for re-admission, quality of life and cost. 99 While this trial showed no significant difference in treatment failure, readmission or emergency surgery requirement, it may have been underpowered as only one hundred and thirty-two patients were randomised (66 to each group). There was no significant difference seen in terms of quality of life assessment at 14 and 60 days but costs for the out-patient group were significantly lower at a third of the cost of in-patient treatment (savings of €1124.70 per patient). Moya et al also described savings of €1600 per patient managed as an outpatient and other studies have shown similar findings.100,101

This is generally consistent with the remaining literature. Pooled rates from a recent metaanalysis including 21 studies and 1781 patients show an overall failure rate of 4.3%, where failure is defined as emergency admission to hospital within 60 days for AD. 98 Subgroup analysis was not able to show an association between recurrent diverticulitis, co-morbidities, peri-colic air, abscess or antibiotic type and treatment failure. However, previous studies have suggested that co-morbidity may predict readmission. 102

Current consensus guidelines agree that there is a potential role for the out-patient management of AD although, the nature of what this entails is less clear.30,83,103–105 At present, much of the mild disease is managed in the community by non-specialists, however a subset of those referred to hospitals will be able to be managed as out-patients once they are appropriately assessed.

Typical Outpatient Regimen

The majority of the studies on out-patient management establish the initial diagnosis based on clinical assessment and cross-sectional imaging with CT. Eligible patients were then given antibiotics in most protocols and started on a liquid only diet, which was gradually progressed over the following days. The most commonly prescribed antibiotics were Amoxicillin-Clavulanic acid or Ciprofloxacin and Metronidazole in penicillin-allergic patients. Duration of antibiotic therapy ranged from 7–14 days in those who gave antibiotics. 82,99,101,106,107

Non antibiotic treatment for diverticulitis

Although this is covered in more detail elsewhere, this review would not be complete without mentioning the recent evidence against the routine use of antibiotics in uncomplicated AD. Administration of antibiotics has been standard of care for treatment of acute uncomplicated diverticulitis. However, recent data from two RCTs suggest antibiotics do not influence outcomes significantly and the role of antibiotics in otherwise healthy individuals is under question. A Swedish RCT of 623 patients found antibiotic treatment for acute uncomplicated diverticulitis neither accelerated recovery nor prevented complications or recurrence. 108 A similar RCT from the Netherlands with 528 patients with CT proven AD found that observational treatment without antibiotics did not prolong recovery and can be considered appropriate in patients with uncomplicated diverticulitis. 109 Both these trials were conducted in an inpatient setting. It is likely that we will see more patients with uncomplicated disease treated with observation in the future and this concept will need to be incorporated into outpatient management.

The role of further investigation after an episode of acute diverticulitis treated as an outpatient

Clinical follow up is important to ensure that the episode of AD has settled. Most recurrence is early and due to failure of the initial episode to settle. 79 Ongoing follow up however is likely of little value, as there is little evidence of any active treatment reducing a further attack. It has been common practise for many patients to have a colonoscopy after an episode of diverticulitis to exclude an underlying colon cancer. Such investigation has a cost and risk (e.g. systemic effects of bowel perforation, colonoscopic perforation) associated with it. Recent evidence suggests that patients who have no pre excising symptoms (e.g. prior change in bowel habit, rectal bleeding and iron deficiency or anaemia ) and who have a good quality CT scan showing uncomplicated diverticulitis are at no greater risk of having a colon cancer that the general community. 110,111

Suggested Exclusion Criteria for Outpatient Management

Based on the exclusion criteria used in the above studies, the following criteria for selecting the appropriate patients for out-patient management are proposed and summarised in the algorithm in .

Radiologic Diagnosis of Complicated disease

The majority of studies exclude patients with radiologically complicated disease including the DIVER Trial and a number of the prospective cohort studies. 99,101,106 A few studies included patients with small pericolic abscesses (defined as <2cm) with acceptable treatment failure rates.112,113 However, given the conflicting evidence on the value of perforation in predicting treatment failure, it is proposed to exclude those with complicated disease. Better standardisation of radiologic classification may improve the ability to predict treatment failure based on imaging more consistently. 93

Immuno-compromised

Immuno-compromise has consistently been used as an exclusion criterion in studies on AD due to the higher morbidity and mortality associated with AD in this population. 114 It has been suggested that immune-compromise may result in a discrepancy between imaging and outcomes where free intra-peritoneal gas may not be associated with the typical pericolic inflammatory appearances that may therefore be missed or under-estimated

Intolerant to Oral Intake

In a survey of Australasian General Surgeons and New Zealand Colorectal Surgeons, intolerance to oral intake was considered an absolute indication for admission in 90 and 86% of respondents respectively. 103

Signs of Severe Sepsis

Hypovolaemia was deemed an absolute indication for admission in 95% NZ Colorectal Surgeon respondents, although simple observations such as a temperature over 38 degrees, a heart rate over 90 beats per minute or a respiratory rate over 20 per minute were less likely to warrant admission in isolation. 103

Lack of Social Support

This is an intuitive exclusion criterion that has been used in all of the studies. Inadequate social support is associated with a higher readmission rate in general surgery. 115

Comorbidity Score

In some of the out-patient protocols, patients with co-morbidities were excluded from out-patient management, while in others (including DIVER) these patients were included regardless. 98,99 Rueda included only those with American Anaesthesiology Association Score of I or II, 102 while Alonso et al excluded patients with diabetes, heart failure, renal insufficiency or obstructive pulmonary disorder. 106 It is likely that it is the frail patients that are the common at risk group for failure of outpatient care.

A systematic review of the predictors of the severe AD identified a Charlson score of 3 or greater as an independent risk factor, 116 a finding echoed in another similar meta-analysis of risk factors for complicated AD. 117 However, in the radiologically diagnosed uncomplicated AD, the evidence is less apparent. 98 Juang et al showed that a Charlson score of 3 or greater did not predict the need for procedural intervention, prolonged admission or readmission in a prospective study of patients with uncomplicated AD. 118 Yoo et al showed no association between the presence of diabetes and need for surgery in their retrospective review of 117 patients with AD. 119 For these reasons comorbidity score is not considered an absolute contra-indication to the out-patient management of uncomplicated AD, but clinical judgement should be used.

Age Criteria

Some studies included age criteria greater than 18 years, 99 others less than 80 102 or 90 years. 101 This appears to be a relatively arbitrary parameter with no actual evidence to support it formally and frailty may be a more meaningful measure, given its association with poorer outcomes in acute general surgery. 120,121

Summary

In summary, AD is a common presentation and is increasing in prevalence. Presentation may be suspected based on clinical and laboratory findings and is routinely investigated with cross sectional imaging (usually CT). Uncomplicated AD may be safely managed as an out-patient in carefully selected patients.

Uncomplicated Diverticulitis

Acute diverticulitis is a common clinical manifestation of colonic diverticula. Diverticular disease has been increasing in prevalence and it is estimated that lifetime risk of developing diverticulitis is around 20%.30 The disease is more common in developed countries and has been associated with dietary habits with high intake of meats and refined sugars and low intake of fiber. 36,122The prevalence also increases with age from around 5% at age 40 to about 65 % by the age of 80. 123 Alcohol has been shown to increase risk of diverticulitis. 124 Smoking is associated with increased risk of developing complications from diverticulitis. 125 Obesity has been increasing in prevalence and studies continue to show association between obesity and risk of developing diverticulitis. 52,126

Acute diverticulitis can be further sub classified into complicated and uncomplicated presentations. Uncomplicated diverticulitis is characterized by inflammation limited to colonic wall and surrounding tissue. Complicated diverticulitis is characterized by colonic inflammation and associated perforation, abscess formation, fistulation or stricture formation. The management of complicated and uncomplicated diverticular disease differs. Most patients with complicated diverticular disease are managed surgically in both elective and emergent settings. Uncomplicated diverticulitis however has been managed successfully non-operatively for decades. Recently there are new data which challenge conventional clinical practice in the management of uncomplicated diverticulitis. This includes use of antibiotics with an acute attack, role of routine endoscopy after uncomplicated diverticulitis and also role of elective surgery after uncomplicated disease. This article will review recent data relevant to these topics.

Antibiotics in Uncomplicated Diverticulitis

Since the advent of antibiotic therapy, antibiotics have been used routinely in the management of patients with acute diverticulitis both in inpatient and outpatient settings. 30,127,128 Recently, investigators have proposed that acute uncomplicated diverticulitis may be an ongoing inflammatory rather than infectious process. 129 This may suggest that the need for antibiotics in management of diverticulitis may be limited. Recent randomized controlled trials support this practice. The AVOD trial (Swedish acronym for “antibiotics in uncomplicated diverticulitis) was a Swedish multicenter, randomized controlled trial. 108 The study included 623 patient with CT confirmed left-sided acute uncomplicated diverticulitis. The patient were divided into two groups. The first group were admitted and received antibiotics. The second group were admitted but only received IV fluids and no antibiotics. Patients with small pericolic abscesses were excluded. The rate of complications of colon perforation and abscess formation was comparable in both groups (No antibiotics vs Antibiotics: Perforation 3 vs 3%: P-value 0.985, Abscess formation 3 vs 0%: P-value 0.080). Seven patients required sigmoid colectomy either during index admission or during follow up in no antibiotics group vs 5 patients in antibiotics group (P-value 0.541). Risk of recurrent disease was 16.2 % in no antibiotics group which was comparable to 15.8 % in antibiotics group (P-value 0.881).

Another trial (DIABOLO) examining this subject was published in 2017. 109 Patient were included from 22 different sites in Netherlands. All patient had CT proven, acute uncomplicated left sided diverticulitis. The primary outcome was recovery during a 6 months follow up period. Secondary outcomes included readmission rate, complicated diverticulitis within 6 months, ongoing and recurrent diverticulitis, need for sigmoid resection and mortality. Median time to recovery was 14 days in observation group compared to 12 days in antibiotics group. The negative secondary outcomes were higher in number in observation group compared to antibiotics group but this was not statistically significant (Complicated diverticulitis: 3.8% vs 2.6% [P-value 0.337], ongoing diverticulitis: 7.3% vs 4.1% [P-value 0.183], recurrent diverticulitis 3.4% vs 3% [P-value 0.494], sigmoid resections: 3.8% vs 2.3% [P-value 0.323], readmissions: 17.6% vs 12% [P-value 0.148], mortality: 1.1% vs 0.4% [P-value 0.432]). However, the authors recognized the possibility of selection bias in the study and possibility of type II error. The study may not be powered to detect possible differences in the secondary outcomes.

In 2018, 2 year follow-up of DIABOLO study was published. 130 There was no difference between groups in terms of recurrent diverticulitis (15.4% in the observational group versus 14.9% in the antibiotic group: P-value 0.885), risk of subsequent episode of complicated diverticulitis (4.8 % vs 3.3 %: P-value 0.403) and need for sigmoid resection (9% vs 5 %: P-value 0.085). Since the DIABOLO trial was not powered for secondary outcomes, these results need to be interpreted and applied in clinical practice with caution. Van Dijk et al looked at quality of life and persistent symptoms after management of uncomplicated diverticulitis with observation versus antibiotics. About one third of patients in each group had persistent symptoms at 1 or 2 years of follow up. No difference was seen in quality of life indices between the two groups. 130 At this time it does appear that there are select patients who can be treated without the use of antibiotics however, further studies are needed to delineate groups that will benefit from this new approach to practice.

Mesalamine, Rifaximin, and Probiotics

As the role of microperforation in the pathophysiology of diverticular disease has come into question, there has been increased interest in the use of immunomodulatory agents in the management of diverticular disease. 5-ASA products and sulfasalazine alter DNA synthesis and cell cycle progression in lymphocytes. Because a low grade proinflammatory state is the proposed mechanism underlying chronic diverticular disease, a number of small trials have evaluated the effectiveness of mesalamine-like compounds. Earlier studies showed some promise of using these agents in management of diverticulitis patients. Trespi et al. demonstrated that patients treated with antibiotics and mesalamine had decreased symptomatology. 131 Another study randomized patients with diverticulitis to a rifaxmin only arm versus a rifaximin/mesalamine arm. 132 Patients in the rifaximin/mesalamine arm demonstrated significantly improved bowel habits. They also had less recurrent episodes and demonstrated lower symptom severity.

However more recent placebo controlled trials have failed to demonstrate clinical effectiveness of these products 133,134. This was confirmed by recent meta-analysis by Urushidani et al. 135 8 RCTs were reviewed in the study which demonstrated that 5-ASA products were not superior to controls in preventing recurrent diverticulitis (RR 0.86, 95% CI 0.63–1.17) or decrease the incidence of adverse events (RR 0.97, 95% CI 0.84–1.11).

The role of the gut microbiome is another topic of recent interest. Agents like rifaximin and probiotics are being investigated alone or in combination with fiber supplements. A meta-analysis from 2011 demonstrated that combination of rifaximin and fiber supplements were effective in reducing symptoms and preventing complications at 1 year. 136 Regarding probiotics, a systematic review in 2016 showed that insufficient data is available currently to comment on role of probiotics in managing diverticular disease. 137 More recent review however demonstrate that certain probiotics may have a role in all stages of diverticular disease and further research is needed to examine its role in management if diverticulitis patients. 138

Surgery for Uncomplicated Diverticulitis

Acute uncomplicated diverticulitis is successfully managed conservatively in majority of patients. However the recurrent nature of disease, risk of potential chronic complications and effect of the disease on the quality of life continues to impact patients at multiple levels. The disease is also a recurrent healthcare burden. Recurrence after an episode of uncomplicated diverticulitis has been reported from 13–67 % in studies with variable follow up periods. 53,56,139–141 Review of literature shows that clinical practice guidelines have gone through multiples changes regarding appropriate surgical managements of these patients.

Clinical practice guidelines in 2000 recommended surgery after two attacks of uncomplicated diverticulitis. 142 In 2006, it was suggested that number of attacks in not necessarily the most important factor in deciding need for surgery and may be younger patients should be considered for surgery due to their higher cumulative risk for recurrent disease. 128 In 2014 individualized approach was recommended for surgery after recovery from uncomplicated acute diverticulitis. 30

Investigators have been interested in identifying appropriate groups of patients to intervene on surgically and the optimal timing of a surgical approach. A single institution retrospective review by Hall et al showed the family history of diverticulitis, length of affected colon > 5 cm and presence of retroperitoneal abscess at index presentation were associated with risk of recurrent disease. 56 Other authors have demonstrated that the risk of recurrence increases with each episode of diverticulitis. Bharucha et al showed the rate of recurrence after first and second episodes of diverticulitis is 22% and 55 % at ten years respectively. 53 At the same time, risk of subsequent complicated disease after an episode of uncomplicated diverticulitis is less than 5 %.56,108,109 Chapman et al showed similar findings where patient with >2 episodes of diverticulitis were not at higher risk of complications compared to patients with 1 or 2 episodes of diverticulitis challenging the idea of offering elective resection after certain number of episodes of uncomplicated diverticulitis. 21 On the other hand, complicated diverticular disease has a higher recurrence rate and recurrent episodes are usually more severe compared to the index presentation. 143 Hence the decision to recommend surgery should not depend on number of episodes of recurrent diverticulitis.

Another area of recent research interest is to compare quality of life in patients receiving conservative management with those undergoing elective sigmoidectomy. One such trial is the DIRECT trial (Surgery versus conservative management for recurrent and ongoing left sided diverticulitis). This study compared surgery versus conservative management for recurrent and ongoing left-sided diverticulitis.144 This is a multicenter randomized controlled trial from Netherlands. Patients aged 18–75 with three recurrent episodes or ongoing symptoms of diverticulitis were randomly assigned to either conservative management or surgical intervention groups. The primary end point of the study was quality of life measured by the Gastrointestinal quality of life index (GIQLI). Secondary end points included additional quality of life assessments and also risk of morbidity and mortality associated with each approach. Mean GIQLI score in surgical group was higher at 6 months compared to conservative management group (P-value 0.0001). Secondary outcomes were also found to be better in surgical group. 23 % of patients in conservative group ultimately required surgical intervention. This trial concluded that surgical intervention, despite its risks, lead to better quality of life compared to patients managed conservatively. Another ongoing trial is Comparison of surgery and medicine on the impact of diverticulitis (COSMID) trail. This is a large scale, randomized controlled trail that will compare outcomes of surgery with best medical management for quality of life limiting diverticulitis. The study will report both patient related and clinical outcomes.

Young patients

Several authors have proposed that patients younger than 40 to 50 years of age present with a move virulent form of diverticulitis. 145,146 Historical recommendations have advocated sigmoid resection for young patients after one well established attack of diverticulitis however, this dictum has been called into question by recent evidence. Data suggest that young age is not necessarily associated with worse clinical outcomes. In a study by Guzzo et al., risk of requiring surgery on initial presentation was similar in patients younger than 50 compared with older population group. 26 One patient out of 196 young patients (< 50 years) had a free perforation after medical management of diverticulitis. Review of large administrative dataset suggested that young patients may indeed have a higher risk of recurrence (27%) but have low and comparable rates of emergency surgical intervention (7.5% vs 5 %). 20 Another retrospective study showed that young patients with CT diagnosed diverticulitis respond well to medical management and have low subsequent risk of emergency surgery and need for colostomy. 147 Given the current level of evidence there is no clear mandate to treat patients with young patients with diverticulitis differently than other age groups.

Clinicians agree now that decision of surgery for uncomplicated diverticulitis is not dependent of factors like age of the patient or number of previous episodes. Rather the decision should be individualized to each patient. Imaging from prior episodes should be reviewed to ensure that prior episodes were properly staged. Attention should be paid to factors like how severe were the prior episodes, how long the antibiotics were needed before resolution of symptoms and whether patient had full resolution of symptoms or still has smoldering symptomatology. The decisions should be based on evaluating risk of surgery with patient’s risk of recurrent disease and persistent symptoms affecting quality of life. 148

Surgical Technique

As role of surgical intervention continues to evolve in management of acute diverticulitis, the role of standardized surgical technique to compare outcomes is becoming equally significant. Laparoscopic surgery is becoming increasingly prevalent in clinical practice. The Sigma trial was a prospective, double blinded, multicenter, randomized controlled trial. 149It compared 104 patients with diverticular disease undergoing either laparoscopic or open surgery. The rate of conversion was 19.4 % in the laparoscopic group. The short term outcomes showed 15.4 % reduction in complication rates, lower post-operative pain, improved quality of life and shorter hospitalization rate in the laparoscopic group of patients. Operating time was longer for laparoscopic surgery. Follow up study of the trial showed that this difference in outcomes between open and laparoscopic approaches decreases over time and at 6 months there was no significant difference between the two groups in terms of mortality and late complications like incisional hernias, bowel obstructions, abscess formation and enterocutaneous fistulas. 150

Authors have also compared the level of proximal and distal transection during the primary operation as it relates to disease recurrence. The purpose of surgery is to remove disease segment of colon and to reestablish intestinal continuity and not to remove all diverticula bearing colon. Proximal resection margin is decided intra-operatively based on anatomy. This is up to area of proximal non inflamed, non-hypertrophied and compliant colon. However since diverticulum is an area of weakening in the colon, care should be taken not to incorporate them in the anastomosis. Distal margin is of great importance in decreasing incidence of recurrent disease. Report from Mayo clinic compared 501 patients undergoing sigmoid colectomy with either colo-sigmoid or colo-rectal anastomosis. Recurrent disease was 12.5 % in colo-sigmoid anastomosis group compared to 6.7 % in colo-rectal anastomosis group. 151 Similar findings were reported by Thaler et al who demonstrated a 4 times higher risk of recurrence if distal sigmoid colon was used for anastomosis compared to upper rectum. 152

Anastomotic leak after colectomy has significant morbidity and mortality. High ligation of inferior mesenteric artery (IMA) is considered important step in oncologic resection for sigmoid and rectal cancers. However this is not considered mandatory in sigmoid resections for diverticular disease. Studies have examined the role of inferior mesenteric artery (IMA) preservation on the rate of anastomotic leak. A retrospective review of 130 patients by Lehmann et al showed no increase in leak rate when IMA was sacrificed. 153 Similar results were reported in a meta-analysis by Cirocchi et al. No statistically significant difference was found in rate of anastomotic leak when IMA was preserved or sacrificed during sigmoid colectomy. 154 This finding has been confirmed in recent studies and meta-analysis. Recent studies are in agreement with these earlier studies. A recent study looked at role of IMA preservation in regards to functional outcomes after sigmoid colectomy. The idea was that more proximal vascular transection will lead to colonic denervation and worse functional outcomes. The study results confirmed that in 54 out 107 patients in whom IMA was preserved, defecatory function and overall quality of life indices were better compared to those in whom IMA was sacrificed. 155 This study highlights the possible role of IMA preservation in improving functional outcomes after diverticular surgery. Overall, currently there is not enough evidence to support routine preservation of IMA in surgical management of diverticular disease.

Tension at colorectal anastomosis is an important technical factor with risk of higher rates of anastomotic strictures and leaks. Splenic flexure mobilization (SFM) is one of the maneuvers undertaken to decrease tension at anastomosis. Cadaveric study showed an additional colon length of 10.7 cm achieved with SFM. This is increased to 28.3 cm with distal transverse colon mobilization. 156 However there is no consensus regarding need for routine SFM for left sided colectomy. Studies in patients with rectal cancers have shown that routine SFM is associated with longer operative time with no difference in anastomotic complications, local recurrence and postoperative morbidity and mortality. 157,158 Recent review on SFM in colon resection for diverticulitis also showed no benefits of routine mobilization and showed a trend towards more minor post-operative complications. 159 Hence while there has been an increase in the use of SFM in patients undergoing laparoscopic surgery for diverticulitis, there appears to be no benefit with routine use of this approach. The decision to perform SFM should be individualized based on intra-operative findings.

Leak test should be routinely performed after colectomy for sigmoid diverticulitis. This will identify suboptimal anastomosis and allow for recreation or repair of anastomosis and guide decision for need to divert proximally. Ricciardi et al showed that rate of clinical leaks was higher in patients with positive intra-operative leak test. He also showed that suture repair after positive leak test was associated with higher postoperative leak rate compared with recreation of anastomosis or proximal diversion. 160

Summary

The management of uncomplicated diverticulitis is changing. Use of antibiotics has been questioned. It appears that antibiotic use can be avoided in select groups of patients. Surgical intervention appears to improve patient’s quality of life. The decision to proceed with surgery is recommended in an individualized manner. Meticulous adherence to standard surgical techniques will help to improve outcomes for patients with this disease.

Complicated Diverticular Disease

Complicated diverticulitis is defined as diverticulitis associated with localized or generalized perforation, localized or distant abscess, fistula, stricture or obstruction. The Hinchey classification system has been used to compare and stratify patients with complicated diverticulitis. Hinchey Stage I diverticulitis is associated with pericolic abscess, Stage II with more distant abscess like pelvic or retroperitoneal abscess, Stage III with purulent diverticulitis and Stage IV patients include those with feculent peritonitis. Modified Hinchey Classification was proposed by Warsavary et al., but the original Hinchey Classification is still the most used clinical classification in practice. ( ) Another modification based on CT findings was proposed as well. 161 ( )

Diverticular abscess

Diverticular abscess can occur in about 10 – 15% of cases. 162 The incidence of diverticular abscess has increased over the last decade likely due to increased utilization of cross-sectional imaging in the last 10 – 20 years. These cases can present either locally around the sigmoid colon (pericolic, mesocolic or pelvic) or at more distant sites in the form of subhepatic abscess. Clinical symptomatology depends on the location of the abscess and the extent of inflammation and peritoneal contamination. Radiological cross-sectional imaging with CT scan is the most effective way to diagnose diverticular abscess. Clinical exam along with the information from cross sectional imaging would help with formulating treatment plans for patients with diverticular abscess. The size of the abscess, its location, presence of loculation and the extent of the peritoneal contamination or presence of peritonitis has been used to decide the treatment algorithm for the individual patient.

Perforated Diverticulitis

Complicated diverticulitis presenting as free perforation occur in about 1% of patients presenting with diverticulitis. Patients may manifest with symptoms of generalized or localized peritonitis at the time of presentation in the emergency room or during the first 24 – 48 hours after admission to the hospital. Free perforation usually occurs on the first attack of diverticulitis and is not usually seen in patients who have had multiple attacks of diverticulitis. Clinical presentation may include signs of localized peritonitis or generalized peritonitis. Generalized peritonitis may present with hemodynamic instability. The presence of feculent or purulent peritonitis, the extent of contamination and hemodynamic status and associated comorbidity decide the treatment options for the patients. 162

Diverticular Fistulas

Fistulas complicating diverticular disease occurs in about 2% of the patients. The localized inflammatory process associated with the colon decompressing into the adjacent viscera leads to the formation of the fistulous process. Fistulous process associated with diverticular disease is usually a chronic presentation and symptomatology associated with the fistula is related to the type of fistula with usually fewer abdominal signs and symptoms. Colo cutaneous fistula could be a sequel of peri colonic abscess. Colo vesical, Colovaginal, coelenteric, Colo colonic, Colo uterine or other common fistulation process. Colo appendiceal, Colo gastric, Colo venous, Colo perineal, Colo perianal, and Colo ureteral are other uncommon internal / external presentations associated with complicated acute diverticulitis. 163–166

Colovesical fistula

Colovesical fistula is the most common type of (65%) of internal fistulation process associated with complicated diverticulitis. It is usually a mature fistula and occurs usually in association with chronic diverticulitis. Colo vesical fistulas are more common in men with a male-to-female ratio of 2 to 3:1 likely due to intervening broad ligament and uterus between the urinary bladder and sigmoid colon. More than 50% of women with colovesical fistula have had previous hysterectomy which supports the above theory. The mean age at the time of presentation is between 55 and 75 years. 166–168 Patients with Colo vesicular fistula typically present with pneumaturia, fecaluria, dysuria and recurrent urinary tract infections. Most patients have urinary tract infections and dysuria. Pneumaturia and fecaluria are pathognomonic symptoms of colovesical fistula and seen in 75% and 50% only respectively. Poppy seed test is diagnostic in 94.6% patients, CT in 60.0%, MRI in 60.0%, retrograde colonic enema in 35.7%, Cystogram in 16.7%, Cystoscopy in 10.2%, and Colonoscopy in 10.2% patients. 164 ( )

Recurrent urinary tract infections could be presenting symptoms without any associated prior episodes of diverticulitis. CT scan of the pelvis is helpful in the diagnosis with inflammation usually localized to the dome of the bladder, with or without air within the lumen of the bladder. Cystoscopy when performed shows inflammation at the dome of the bladder and on occasion, food material like vegetable matter could be seen in the urine.

Colovaginal and Colouterine fistula

Colovaginal fistulas are the most common diverticular fistula to the female genital organ and most commonly occur in older women with history of prior hysterectomy. History of diverticulitis preceding colovesical fistula diagnosis is noted in only a third of the patients. Presenting symptoms include vaginal discharge (95%), passage of air or stool through the vagina. Abdominal pain is reported in only 50% of patients. 166,169 These patients usually present to their primary physicians or were seen by their gynecologist. Cross sectional imaging would help with the diagnosis with the inflammatory process involving the colon over the vaginal cuff. ( ) An opening seen at the apex of the vagina is seen in 30–87% patients, and most commonly on the left side. 169,170

Colouterine fistulas are rare phenomenon and literature about them is limited to case reports only. It is more likely that colouterine fistulas are likely from non-diverticulitis related etiology like secondary to obstetric trauma, pelvic malignancy and effects of radiation therapy.

Colocutaneous fistula

Colo cutaneous fistula is uncommon and result from inadvertent incision and drainage of abdominal wall abscess associated with acute complicated diverticulitis associated with parietal wall abscess. ( & ) Patients who have had percutaneous drainage of diverticular abscess may also present with Colo cutaneous fistula prior to their elective resection. Patients who have had sigmoid colectomy for diverticular disease with anastomosis to the distal sigmoid rather than proximal rectum are at higher risk for Colocutaneous fistula with recurrent diverticulitis involving the distal sigmoid colon. Patients with Colocutaneous fistula may also have unsuspected Crohn’s disease. 171

Coloenteric Fistula

Coloenteric fistulas are uncommon fistulas and comprise between 3 to 7% of all diverticular fistulas. 166,172 It is usually between a redundant sigmoid colon and terminal ileum and less commonly with jejunal loops. Presenting symptoms include diarrhea, which presents as sudden development of severe watery diarrhea. Abdominal pain and weight loss secondary to diarrhea are other common presenting symptoms. CT scan may help with the diagnosis and malignant fistula should be excluded with colonoscopy. 173 Coloenteric fistula may be accompanied by distal sigmoid stricture as well. 174

Colonic Stricture and obstruction

Colonic stricture and obstruction can have either an acute or may have a more chronic clinical presentation. ( ) Complicated diverticulitis with significant inflammation can present with an inflammatory stricture or phlegmon can present with partial or complete large bowel obstruction. These patients would require more urgent surgical intervention.

Patients who have had multiple episodes of diverticulitis over many years treated conservatively may present with chronic left lower quadrant cramping abdominal pain. Barium enema or flexible sigmoidoscopy may demonstrate the obstruction and usually mandate surgery to address obstruction. Colon cancer and ischemic strictures are important differential diagnosis when large bowel obstruction is the presentation.

Diverticular hemorrhage

Diverticular bleeding accounts for nearly 200,000 hospital admissions in the United States annually and occurs in 3–5% of patients with diverticulosis. It usually presents as painless, intermittent and large volume lower GI bleeding. 174 Diverticular bleeding is the most common cause of lower gastrointestinal bleeding, accounting for 20.8 to 41.6% of cases of lower gastrointestinal bleeding. 175

Advanced age, NSAID, anticoagulant as well as antiplatelet use are the most common risk factors for the incidence diverticular bleed. 176 The nature and color of the bleeding depends on the intensity of the bleeding, with right sided diverticular bleeding presenting more like Malena and left sided diverticular bleeding present as bright red bleeding per rectum. In stable patients, colonoscopy remains the gold standard in diagnosis and treatment of diverticular bleeding. Stigmata of bleeding, including active hemorrhage, visible vessel, adherent clot to the diverticulum are diagnostic of diverticular hemorrhage. 177 Patient factors, such as the use of oral anticoagulants or antiplatelet agents, hemorrhagic shock on presentation and major stigmata of bleeding in colonoscopy are risk factors for rebleeding. 178,179 Patients who remain hemodynamically unstable after initial resuscitation and are unable to tolerate a bowel preparation for colonoscopy, should get a CT angiography, followed by embolization if an active bleeding source has been identified. 180

Immunocompromised Patients

Patients with immunocompromised status and acute diverticulitis are a special category of patients and managed differently. This group of patients include those with immunocompromised disease like untreated HIV, organ transplant recipients on immunosuppressants, systemic steroids, diabetes mellitus, renal failure, cirrhosis and underlying malignancy patients on chemotherapy or radiation therapy. Immunocompromised patients are more likely to present with free perforation due to inability to mount appropriate inflammatory response to the acute events. These patients are likely to require emergency surgery with resultant increased risk of perioperative complications. 181

Role of Colonoscopy

After an episode of acute diverticulitis, routine colonoscopy has been recommended by ACPBGI and ASCRS. Colonoscopy is advocated to exclude the presence of colorectal cancer or presence of alternative diagnosis like is