Colonic Diverticulitis

ByJoel A. Baum, MD, Icahn School of Medicine at Mount Sinai;
Rafael Antonio Ching Companioni, MD, HCA Florida Gulf Coast Hospital
Reviewed/Revised Oct 2022
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Diverticulitis is inflammation with or without infection of a diverticulum, which can result in phlegmon of the bowel wall, peritonitis, perforation, fistula, or abscess. The primary symptom is abdominal pain. Diagnosis is by CT. Treatment is with bowel rest, sometimes antibiotics, and occasionally surgery.

A colonic diverticulum is a saclike pouch of colonic mucosa and submucosa that protrudes through the muscular layer of the colon; because it does not contain all layers of the bowel, it is considered a pseudodiverticulum (see also Definition of Diverticular Disease).

Many people have multiple colonic diverticula (diverticulosis). The incidence of diverticulosis rises with increasing age; it is present in 75% of people > 80 years. In people > 50 years, acute diverticulitis is most common among women; in those < 50 years, it is most common among men. Patients with HIV and those undergoing chemotherapy are at increased risk of developing acute diverticulitis (1).

Diverticula are usually asymptomatic but sometimes become inflamed (diverticulitis). One study reported that 4.3% of patients with documented diverticulosis developed diverticulitis over an 11-year follow-up period (2).

Diverticulitis that is managed nonoperatively can recur as either an acute or chronic process. The risk of a recurrent acute episode is up to 39%, although reported rates vary widely (3). A large population-based study found that after an episode of acute diverticulitis the recurrence rate at 1 year was 8% and at 10 years was 22% (4). About half of second episodes of diverticulitis occur within 12 months. In some patients, however, recurrence manifests as chronic, ongoing abdominal pain; this may develop after one or more acute episodes.

General references

  1. 1. Francis NK, Sylla P, Abou-Khalil M, et al: EAES and SAGES 2018 consensus conference on acute diverticulitis management: Evidence-based recommendations for clinical practice. Surg Endosc 33(9):2726–2741, 2019.

  2. 2. Shahedi K, Fuller G, Bolus R, et al: Long-term risk of acute diverticulitis among patients with incidental diverticulosis found during colonoscopy. Clin Gastroenterol Hepatol 11(12):1609–1613, 2013. doi: 10.1016/j.cgh.2013.06.020

  3. 3. Sallinen V, Mali J, Leppäniemi A, Mentula P: Assessment of risk for recurrent diverticulitis: A proposal of risk score for complicated recurrence. Medicine (Baltimore) 94(8):e557, 2015. doi: 10.1097/MD.0000000000000557

  4. 4. Bharucha AE, Parthasarathy G, Ditah I, et al: Temporal trends in the incidence and natural history of diverticulitis: A population-based study. Am J Gastroenterol 110(11):1589–1596, 2015. doi: 10.1038/ajg.2015.302

Etiology of Colonic Diverticulitis

Gastrointestinal Myths

The etiology and pathophysiology of diverticulitis are not fully understood and may vary among patients. It has long been thought that diverticulitis occurs when a micro or macro perforation develops in a diverticulum, resulting in the release of intestinal bacteria and triggering inflammation. However, emerging data suggest that in some patients, acute diverticulitis is more of an inflammatory than infectious process. Furthermore, cytomegalovirus may be a trigger of that inflammation; active viral replication has been found in affected colon tissue in over two thirds of patients with diverticulitis.

Studies have suggested a direct correlation between red meat consumption per week, smoking, obesity, and the incidence of diverticulitis (1, 23, 4). There is no association between consumption of nuts, seeds, corn, or popcorn and development of diverticulitis as was previously thought. Physical activity and dietary fiber have been shown to help prevent formation of diverticula and development of diverticulitis (3, 4).

Etiology references

  1. 1. Cao Y, Strate LL, Keeley BR, et al: Meat intake and risk of diverticulitis among men. Gut pii: gutjnl-2016-313082, 2017. doi: 10.1136/gutjnl-2016-313082

  2. 2. Strate LL, Keeley BR, Cao Y, et al: Western dietary pattern increases, and prudent dietary pattern decreases, risk of incident diverticulitis in a prospective cohort study. Gastroenterology 152(5):1023–1030.e2, 2017. doi: 10.1053/j.gastro.2016.12.038

  3. 3. Bohm SK, Kruis W: Lifestyle and other risk factors for diverticulitis. Minerva Gastroenterol Dietol 63(2):110–118, 2017. doi: 10.23736/S1121-421X.17.02371-6

  4. 4. Schultz JK, Azhar N, Binda GA, et al: European Society of Coloproctology: Guidelines for the management of diverticular disease of the colon. Colorectal Dis 22 (supplement 2):S5–S28, 2020. doi: 10.1111/codi.15140

Classification of Colonic Diverticulitis

Acute diverticulitis can be classified as

Complications can develop after perforation of an inflamed diverticulum.

About 15% of patients with acute complicated diverticulitis have a pericolic or intramesenteric abscess.

If acute diverticulitis does not heal completely, chronic diverticulitis will develop.

Chronic diverticulitis can be classified as

  • Chronic uncomplicated diverticulitis: Defined as thickening of the colonic wall or chronic mucosal inflammation in the absence of stricture

  • Chronic complicated diverticulitis: Includes stenotic disease, which may cause acute colon obstruction and fistula formation (most commonly to the bladder)


Symptoms and Signs of Colonic Diverticulitis

Patients have left lower quadrant abdominal pain and tenderness and often have a palpable sigmoid; pain is occasionally suprapubic. However, Asian patients with diverticulitis often present with right-sided pain due to right colon involvement. The pain can be accompanied by nausea, vomiting, fever, and sometimes even urinary symptoms as a result of bladder irritation. Peritoneal signs (eg, rebound or guarding) may be present, particularly with abscess or free perforation. Fistula may manifest as pneumaturia, fecaluria (feces in the urine), feculent vaginal discharge, or a cutaneous or myofascial infection of the abdominal wall, perineum, or upper leg. Patients with bowel obstruction have nausea, vomiting, and abdominal distention. Bleeding is uncommon.

Recurrent episodes of acute diverticulitis manifest similar to initial episodes; they are not necessarily more severe.

Diagnosis of Colonic Diverticulitis

  • Abdominal and pelvic CT

  • Colonoscopy after resolution

Clinical suspicion is high in patients with known diverticulosis who present with characteristic abdominal symptoms. However, because other disorders (eg, appendicitis, colon or ovarian cancer, inflammatory bowel disease) may cause similar symptoms, testing is required.

Diverticulitis is evaluated with CT of the abdomen and pelvis with water-soluble contrast given orally and rectally; IV contrast also is given when not contraindicated. However, findings in about 10% of patients cannot distinguish diverticulitis from colon cancer. MRI is an alternative for pregnant and young patients (1, 2).

Colonoscopy is often recommended 1 to 3 months after resolution of the episode to assess for cancer. However, in the absence of high-risk signs (eg, complicated diverticulitis, uncomplicated diverticulitis with imaging abnormalities or atypical course, family history of colorectal cancer, anemia, weight loss), the likelihood of malignant lesions or advanced adenomas after an episode of acute uncomplicated diverticulitis is low (2).

Diagnosis references

  1. 1. Stewart DB: Review of the American Society of Colon and Rectal Surgeons clinical practice guidelines for the treatment of left-sided colonic diverticulitis. JAMA Surg 156(1):94–95, 2021. doi: 10.1001/jamasurg.2020.5019

  2. 2. Francis NK, Sylla P, Abou-Khalil M, et al: EAES and SAGES 2018 consensus conference on acute diverticulitis management: Evidence-based recommendations for clinical practice. Surg Endosc 33(9):2726–2741, 2019. doi: 10.1007/s00464-019-06882-z

Treatment of Colonic Diverticulitis

  • Varies with severity

  • Sometimes antibiotics

  • CT-guided percutaneous drainage of abscess

  • Sometimes surgery

A patient who is not very ill is treated at home with rest. Symptoms usually subside rapidly. An unrestricted diet, if tolerated, is preferable for patients with acute uncomplicated diverticulitis. No data support dietary restrictions.


Antibiotics were traditionally recommended for all cases of acute diverticulitis whether or not they were complicated. However, data suggest that antibiotics may not improve outcome in uncomplicated diverticulitis, therefore, patients who are otherwise healthy and have uncomplicated sigmoid diverticulitis can be safely managed without antibiotics. (See also the American Gastroenterological Association's 2015 guidelines on management of acute diverticulitis.)

Antibiotic therapy should be reserved for patients with acute complicated diverticulitis, immunosuppression, sepsis, or significant comorbidities.

If antibiotics are used, they should cover gram-negative rods and anaerobic bacteria.

Oral antibiotic regimens that can be given to outpatients for whom treatment is elected include 7 to 10 days of

IV antibiotic regimens for hospitalized patients are selected based on many factors, including the severity of illness, risk of adverse outcome (eg, due to other illnesses, older age, immunosuppression), and likelihood of resistant organisms. Many regimens exist.

There are no well-defined standards relating abscess size to the need for surgery or interventional (ultrasound- or CT-guided) drainage. However, small pericolic abscesses (less than 2 to 3 cm in diameter) often resolve with broad-spectrum antibiotics and bowel rest alone.

Percutaneous drainage or endoscopic ultrasound-guided drainage

CT-guided percutaneous or endoscopic ultrasound-guided drainage is becoming the standard of care for larger abscesses (over 3 cm in diameter), for abscesses that do not resolve with antibiotics, and/or for clinical deterioration. However, abscesses that are multiloculated, inaccessible, or not improving with drainage require surgical intervention.


Surgery is required immediately for patients with free perforation or when feculent peritonitis is suspected based on clinical examination or imaging. Other indications for surgery include severe symptoms that do not respond to nonsurgical treatment within 3 to 5 days and increasing pain, tenderness, and fever. About 15 to 20% of people admitted with acute diverticulitis require surgery during that admission (1).

For uncomplicated diverticulitis, surgical resection was previously recommended based on the number of recurrences. Currently, the American Society of Colon and Rectal Surgeons (ASCRS) and other practice guidelines recommend a case-by-case evaluation rather than mandatory elective segmental colectomy after a second episode (26; see also the Japan Gastroenterological Association's 2019 guidelines for colonic diverticular bleeding and colonic diverticulitis and the ASCRS' 2020 guidelines for the treatment of left-sided colonic diverticulitis). Patients for whom recurrent attacks pose a higher risk of death or complications are typically considered candidates for surgery.

For complicated diverticulitis, surgical recommendations vary. An elective segmental colectomy is not routinely recommended for patients after a conservatively managed episode of acute complicated diverticulitis (7). Surgery is recommended for patients with chronic complicated diverticulitis where fistulas and persisting abscesses are present.

The involved section of the colon is resected. The ends can be reanastomosed immediately in healthy patients without perforation, abscess, or significant inflammation. Other patients have a temporary colostomy with anastomosis carried out in a subsequent operation after inflammation resolves and their general condition improves.

Treatment references

  1. 1. Wieghard N, Geltzeiler CB, Tsikitis VL: Trends in the surgical management of diverticulitis. Ann Gastroenterol 28(1):25–30, 2015.

  2. 2. Feingold D, Steele SR, Lee S, et al: Practice parameters for the treatment of sigmoid diverticulitis. Dis Colon Rectum 57:284–294, 2014. doi: 10.1097/DCR.0000000000000075

  3. 3. Regenbogen SE, Hardiman KM, Hendren S, Morris AM: Surgery for diverticulitis in the 21st century: A systematic review. JAMA Surg 149(3):292–303, 2014. doi: 10.1001/jamasurg.2013.5477

  4. 4. Comparato G, Di Mario F: Recurrent diverticulitis. J Clin Gastroenterol 42(10):1130–1134, 2008. doi: 10.1097/MCG.0b013e3181886ee4

  5. 5. Young-Fadok TM: Diverticulitis. N Engl J Med 379(17):1635–1642, 2018. doi: 10.1056/NEJMcp1800468

  6. 6. Stewart DB: Review of the American Society of Colon and Rectal Surgeons clinical practice guidelines for the treatment of left-sided colonic diverticulitis. JAMA Surg 156(1):94–95, 2021. doi: 10.1001/jamasurg.2020.5019

  7. 7. Schultz JK, Azhar N, Binda GA, et al: European Society of Coloproctology: Guidelines for the management of diverticular disease of the colon. Colorectal Dis 22 (supplement 2):S5–S28, 2020. doi: 10.1111/codi.15140

Key Points

  • Diverticulitis is inflammation and/or infection of a diverticulum.

  • Inflammation remains uncomplicated in about 75% of patients; the remainder develop abscesses, peritonitis, bowel obstruction, or fistulas.

  • Diagnose using abdominal and pelvic CT with oral, rectal, and IV contrast; do colonoscopy 1 to 3 months after the episode to look for cancer.

  • Management depends on severity but typically includes conservative management, often antibiotics, and sometimes percutaneous or endoscopic ultrasound-guided drainage or surgical resection.

More Information

The following English-language resources may be useful. Please note that THE MANUAL is not responsible for the content of these resources.

  1. American Gastroenterological Association: Guidelines on management of acute diverticulitis (2015)

  2. Japan Gastroenterological Association: Guidelines for colonic diverticular bleeding and colonic diverticulitis (2019)

  3. American Society of Colon and Rectal Surgeons: Guidelines for the treatment of left-sided colonic diverticulitis (2020)

Segmental Colitis Associated With Diverticulosis (SCAD)

Segmental colitis associated with diverticular disease refers to chronic colonic inflammation affecting the interdiverticular mucosa. Diagnosis is by endoscopy. Treatment is symptomatic.

(See also Colonic Diverticulosis.)

Segmental colitis associated with diverticulosis (SCAD) and chronic recurrent diverticulitis are terms used to describe chronic colonic inflammation attributed to diverticulosis. SCAD usually affects the interdiverticular mucosa and is usually present on the left side sparing the rectum and ascending colon.

The cause of SCAD is unknown and may be multifactorial. Mucosal prolapse, fecal stasis, localized ischemia, alterations in the gut microbiota, and/or chronic inflammation may play a role. It is unclear how much the relationship between the diverticulosis and colitis is causal, is due to a common underlying factor, or is coincidental: the histologic characteristics contain features similar to those seen in inflammatory bowel disease, infectious colitis, and ischemic colitis. The prevalence of SCAD in people with diverticulosis is very low (1%). SCAD usually affects males > 60 years of age.

Symptoms of SCAD include hematochezia, abdominal pain, and diarrhea.

The diagnosis of SCAD is suggested when endoscopy reveals erythematous, friable, and granular mucosa with either a diffuse or patchy distribution involving the interdiverticular mucosa.

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