Diverticulitis

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Diverticulitis is a diverticular disease caused by inflammation of colonic diverticula and occurs as a complication of diverticulosis, more commonly in older adults. It may remain localized (mild uncomplicated diverticulitis) or progress, resulting in complications such as abscess or perforation (complicated diverticulitis). Diverticulitis typically manifests with fever and left lower quadrant abdominal pain as the sigmoid colon is most commonly involved. CT abdomen with IV contrast is the preferred diagnostic modality in suspected acute diverticulitis. Uncomplicated diverticulitis usually responds to conservative management with bowel rest and analgesics; oral broad-spectrum antibiotics are reserved for patients at high risk of complications. In complicated diverticulitis, management consists of parenteral antibiotics, treatment of any complications, and, in some cases, emergency colonic resection. Once the acute phase has resolved, a colonoscopy is often performed to rule out malignancy. Elective colectomy is recommended for all patients with complicated diverticulitis that is managed conservatively. The procedure is not routinely indicated for uncomplicated diverticulitis.

See also “Diverticulosis.”

Inflammation or infection of colonic diverticula (typically false diverticula caused by weakness in the intestinal wall) ^[2][3]

• Incidence ^[4][5]
  • 188/100,000 person-years ^[5]
  • Increases with age
  • Occurs in ∼ 4–20% of individuals with diverticulosis
• Disease burden ^[4]
  • Accounts for > 165,000 annual hospital admissions in the US.
  • Likelihood of requiring surgery: ∼ 15%
  • Mortality: ∼ 1%

Epidemiological data refers to the US, unless otherwise specified.

• Possible risk factors include: ^[6]
  • Consumption of red meat ^[7][8]
  • Elevated BMI (especially due to visceral fat)
  • Smoking
  • Inherited connective tissue diseases: Marfan syndrome, Ehlers-Danlos syndrome, Williams-Beuren syndrome
  • HIV infection
  • Chemotherapy
• Perforated diverticulitis risk may be increased by NSAIDs, opioids, and corticosteroids. ^[6]
• See “Diverticulosis” for etiologies of the formation of diverticula.

• Formation of diverticula (most commonly in the sigmoid colon): a combination of increased intraluminal pressure (e.g., due to chronic constipation) and age-related or physiological weakness of the intestinal wall (See “Diverticulosis.”)
• Inflammation
  • Most commonly: chronic inflammation and increased intraluminal pressure → erosion of diverticula wall → inflammation and bacterial translocation
  • Rarely: stool becomes lodged in diverticula → obstruction of intestinal lumen → inflammation

• Low-grade fever
• Sigmoid colon most commonly affected → left lower quadrant pain
• Possibly tender, palpable mass (pericolonic inflammation)
• Change in bowel habits (constipation in ∼ 50% of cases and diarrhea in 25–35% of cases)
• ↑ Urinary urgency and frequency (in ∼ 15% of cases), sterile pyuria
• Acute abdomen: indicates possible perforation and peritonitis
• Rarely: hematochezia

In elderly or immunocompromised patients, clinical symptoms may only be mild.

Recommendations in this section are consistent with the 2021 American Gastroenterological Association (AGA) guidelines on the medical management of diverticulitis and the 2018 joint European Association for Endoscopic Surgery (EAES) and Society of American Gastrointestinal and Endoscopic Surgeons (SAGES) consensus statements on acute diverticulitis management. ^[6][9]

Approach ^[9][10][11]

• Suspect acute diverticulitis in adult patients presenting with LLQ pain, fever, and leukocytosis.
• The diagnosis is typically confirmed with imaging, preferably CT abdomen with IV contrast.
  • Consider obtaining imaging in patients with:
    • An unclear diagnosis
    • Immune deficiency
    • Poor response to treatment
    • Recurrent disease for which surgery is being considered
  • Can defer imaging in patients with a prior history of diverticulitis who have:
    • Symptoms similar to previous episodes
    • No signs of severe or complicated disease
• Consider colonoscopy to screen for malignancy once the acute phase has resolved and the risk of perforation is reduced.

Women presenting with LLQ pain should receive a pelvic examination in order to assess for gynecologic etiologies. ^[11]

Laboratory studies ^[10][12][13]

• CBC: leukocytosis, possible anemia
• BMP: electrolyte abnormalities, ↑ BUN, ↑ creatinine
• CRP: ↑ CRP
• FOBT: positive in patients with diverticular bleeding
• Consider the following to rule out common differential diagnoses based on pretest probability:
  • Urinalysis: to rule out UTI and nephrolithiasis
  • Urine or serum β-hCG: to rule out pregnancy, including complications of ectopic pregnancy in all women of reproductive age
  • Stool microscopy: to rule out gastroenteritis
  • See also “Diagnostics” in “Acute abdomen”.

Diverticulitis is highly likely in patients with LLQ pain and tenderness, no vomiting, and CRP > 50 mg/L. ^[6]

Imaging ^{[10][13][14][15][16][17]}

• CT abdomen and pelvis with IV contrast ^[14]
  • Indications
    • Preferred initial imaging modality for suspected diverticulitis ^[6][14]
    • Diagnostic confirmation in patients with no prior imaging studies ^[9]
    • Staging the severity of diverticulitis (see modified Hinchey classification of diverticulitis)
  • Supportive findings
    • Colonic outpouching
    • Signs of inflammation
      • Bowel wall thickening > 3 mm
      • Peridiverticular mesenteric fat stranding
    • Complications may also be identified
      • Peridiverticular abscess: hypodense collections with peripheral contrast enhancement
      • Diverticular perforation: pneumoperitoneum
      • Intestinal obstruction: dilated intestinal loops with multiple air-fluid levels
• MRI abdomen and pelvis (without and with IV contrast)
  • Indications: suspected diverticulitis in patients with contraindications to CT ^[14]
  • Findings: similar to those on CT scan
• Ultrasound abdomen
  • Indications
    • Formal ultrasound is typically considered as an alternative to MRI in patients with contraindications to CT
    • Point-of-care ultrasound may be considered as an initial imaging modality and can show findings of complicated diverticulitis (e.g., pneumoperitoneum, free fluid, abscess formation). ^[18]
  • Supportive findings: diverticula with surrounding inflammation (hyperechoic), abscess formation (detectable fluid), bowel wall thickening
• Abdominal x-ray ^[13]
  • Not useful in diagnosing uncomplicated diverticulitis
  • Indications
    • Suspected perforation or bowel obstruction
    • May be performed as part of the routine workup for acute abdominal pain
  • Findings that may be seen in complicated diverticulitis include
    • Bowel perforation: pneumoperitoneum
    • Bowel obstruction: dilated bowel loops and multiple air-fluid levels
• Screening colonoscopy ^{[10][13][16][19]}
  • Recommended 6–8 weeks after the resolution of the acute episode to assess the extent of diverticulitis and rule out malignancy ^[6][9][10]
  • Colonoscopy is contraindicated during an acute episode because of the increased risk of perforation.
  • Not required if a recent evaluation of the colon has been performed ^[19]

Avoid colonoscopy during the acute phase of diverticulitis because of the risk of perforation!

• To choose the best treatment approach and determine the prognosis, identifying the stage of acute diverticulitis is recommended. ^[13]
  • Uncomplicated diverticulitis: localized inflammation of a colonic diverticulum with no evidence of complications (i.e., Modified Hinchey stage 0 and stage Ia)
  • Complicated diverticulitis: inflammation of a colonic diverticulum associated with complications such as perforation, abscess, fecal peritonitis, bowel obstruction, or fistula formation (i.e., Modified Hinchey stages Ib–IV) ^[10]
• The modified Hinchey classification is based on CT findings and is the most commonly used classification. ^[6]

• Differential diagnoses of uncomplicated acute diverticulitis
  • Crohn disease, ulcerative colitis
  • Colorectal cancer
  • Intestinal ischemia (ischemic colitis)
  • Acute appendicitis
  • Ileus , colonic obstruction
  • Ectopic pregnancy
  • Ovarian torsion
  • Ovarian cancer
  • Inguinal hernia
  • Renal colic
  • Urinary tract infection
• Differential diagnoses of perforated diverticulitis: See “Gastrointestinal perforation.”
• See also “Differential diagnoses of acute abdomen.”

The differential diagnoses listed here are not exhaustive.

Recommendations in this section are consistent with the 2021 American Gastroenterological Association (AGA) guidelines on the medical management of diverticulitis and the 2018 joint European Association for Endoscopic Surgery (EAES) and Society of American Gastrointestinal and Endoscopic Surgeons (SAGES) consensus statements on acute diverticulitis management. ^[6][9]

Approach ^[11][17][21]

• Uncomplicated diverticulitis (Modified Hinchey stage 0 and stage Ia)
  • Conservative management ^[13][17]
  • Consider broad-spectrum oral antibiotics (e.g., ciprofloxacin PLUS metronidazole) in select patient groups.
• Complicated diverticulitis (Modified Hinchey stages Ib–IV)
  • Inpatient management with broad-spectrum IV antibiotics is recommended.
  • CT-guided percutaneous drainage for abscesses > 4 cm
  • Emergency colectomy in patients with generalized peritonitis

Consider imaging, antibiotic therapy, and surgical consultation early for immunocompromised patients, as they are at high risk of developing severe or complicated disease. ^[9]

Uncomplicated diverticulitis ^{[6][9][11][13][17]}

• Antibiotic therapy: Recommended on a selective basis (not routinely) ; ^{[9][16][19][22]}
  • Indications ^{[9][16][22][23]}
    • Clinical presentation
      • Signs of generalized infection (e.g., fever)
      • Persistent symptoms
      • Vomiting
    • Preexisting conditions
      • Pregnancy
      • Immunosuppression
      • Frailty
      • Comorbidities
    • Diagnostic findings
      • CRP > 140 mg/L or WBC count > 15,000/mm³
      • Fluid collection and/or extensive inflammation on CT
  • Options: Consider any of the following broad-spectrum oral antibiotics. ^[22][23]
    • Metronidazole PLUS one of the following: ^[22]
      • Ciprofloxacin
      • Levofloxacin ^[22]
      • Trimethoprim-sulfamethoxazole ^[22]
    • Amoxicillin/clavulanate ^[22]
    • Moxifloxacin ^[22]
    • See also ”Empiric antibiotic therapy for intra-abdominal infections.”
  • Duration of therapy: 4–7 days ^[16]
• Supportive care
  • Relative bowel rest: clear liquid diet until improvement of symptoms
  • Analgesics as needed (see “Acute pain management.”) ^[11]
    • First-line treatment for mild to moderate disease: acetaminophen and antispasmodics (e.g., dicyclomine)
    • Reserve use of NSAIDs and opioid analgesics for refractory pain.
  • Antiemetics as needed
• Disposition and follow-up
  • Outpatient treatment ^[6]
  • Follow-up in 2–3 days for evaluation of progression (earlier if symptoms worsen)
  • If no improvement: Consider inpatient management; repeat imaging to evaluate for complications.
  • Screening colonoscopy (after the first episode) once symptoms have resolved if the patient has not had a colonoscopy within the past year ^[6][9]
  • Consider surgical consult for recurrent uncomplicated diverticulitis.
  • GI consultation for patients with frequent, recurrent episodes, chronic symptoms, or unclear diagnosis (e.g., possible inflammatory bowel disease) ^[11][22]

Patients without severe symptoms or comorbidities can be managed in an outpatient setting if they have uncomplicated diverticulitis, oral intake is tolerated, and adequate follow-up can be ensured. ^[11]

Complicated diverticulitis ^{[6][11][16][17][19][22]}

• Antibiotic therapy: broad-spectrum IV antibiotics are routinely recommended (see “Empiric antibiotic therapy for intra-abdominal infections.”)
• Management of complications
  • Abscess ^[13][17][24]
    • Size < 4 cm: trial of conservative management with IV antibiotics
      • Signs of improvement in 48–72 hours: Start enteral feeds; consider switching to oral antibiotics.
      • No signs of improvement in 48 hours: Repeat imaging and consider percutaneous drainage.
    • Size ≥ 4 cm
      • Ultrasound- or CT-guided percutaneous drainage
      • Consider laparoscopic or open surgical drainage if percutaneous drainage is not feasible.
      • Continue IV antibiotic therapy.
      • Send aspirate or pus for cultures and tailor antibiotic treatment accordingly.
  • Perforation with generalized peritonitis (i.e., clinical signs of diffuse peritonitis or modified Hinchey stage III and stage IV on imaging): emergency surgery ^[6][16][17]
    • Hemodynamically stable patients: laparoscopic or open colectomy and primary anastomosis with/without a temporary diverting stoma
    • Critically ill patients: Hartmann procedure
  • Bowel obstruction
    • See “Treatment of paralytic ileus.”
    • See “Management of bowel obstruction.”
• Supportive care
  • Complete bowel rest (NPO)
  • IV fluids (see IV fluid therapy)
  • Analgesics as needed (see acute pain management)
  • Antiemetics as needed (see antiemetics)
• Disposition and follow-up: inpatient treatment with surgery and/or interventional radiology consultation
  • Screening colonoscopy once symptoms have resolved if the patient has not had a colonoscopy within the past year ^[9]
  • Consider surgical consult for elective colectomy if not performed during admission.

Obtain an urgent surgical consult in patients with features of generalized peritonitis or sepsis.

Long-term management

• Elective colectomy ; ^{[10][13][17][19]}
  • Indications
    • Routinely recommended 6–8 weeks after resolution of complicated diverticulitis
    • Select groups of patients after resolution of uncomplicated diverticulitis, including: ^[13][16][17]
      • Patients at high risk of recurrence with complications ^[13]
      • Patients with persistent abdominal symptoms after resolution of an acute episode
    • Chronic complications of diverticulitis (e.g., fistula, colonic strictures)
  • Procedure: laparoscopic or open colectomy ^[13][16]
• Secondary prevention (reducing recurrence risk) ^[9][16][19]
  • Avoid nonaspirin NSAID use, if possible.
  • The use of mesalamine, rifaximin, or probiotics to prevent recurrences is no longer recommended. ^[9]
  • See “Prevention” in “Diverticulosis” for primary prevention of diverticulitis, e.g., dietary and lifestyle modification.

Uncomplicated diverticulitis ^[6][9][10]

• Clear liquid diet
• Supportive care
• Consider broad-spectrum oral antibiotics in patients at high risk for complications (not routinely indicated). ^[23]
• Outpatient treatment with follow-up in 2–3 days or earlier if symptoms worsen
• Consider referral for colonoscopy after the resolution of symptoms

Complicated diverticulitis ^{[6][9][17][24]}

• Urgent surgery consult
• NPO
• IV fluids
• Broad-spectrum IV antibiotics: See empiric antibiotic therapy for intra-abdominal infections.
• Manage complications, if present.
  • Perforation with fecal peritonitis: See bowel perforation.
  • Bowel obstruction: See “Bowel obstruction” and “Paralytic ileus.”
  • Abscess
    • Size < 4 cm: Continue antibiotics.
    • Size ≥ 4 cm: IR consult for image-guided percutaneous drainage
• Parenteral analgesics (see acute pain management)
• Parenteral antiemetics
• Inpatient treatment
• Serial abdominal examination for patients not undergoing emergency surgery
• Refer for colonoscopy after the resolution of symptoms

Early ^[20]

• Perforation
  • Locally-contained perforation: can lead to the formation of an abscess or phlegmon ^[20]
  • Intraperitoneal perforation
    • Caused by:
      • Rupture of an inflamed diverticulum; → free communication with the peritoneum → generalized fecal peritonitis
      • Rupture of a diverticular abscess → generalized purulent peritonitis
    • Can present with symptoms of acute abdomen and widespread intraperitoneal free air on imaging
• Abscess
  • Peridiverticular localization
  • Causes symptoms similar to those of acute diverticulitis
  • Suspect an abscess in patients with persistent fever and abdominal pain despite antibiotic treatment.
• Intestinal obstruction (rare)
  • Etiology
    • Narrowing due to inflammatory swelling
    • Compression through abscesses
    • Ileus caused by localized irritation
  • Clinical findings
    • Abdominal pain and distention
    • Constipation
    • Nausea, vomiting
    • Acute abdomen
• Bleeding: Although diverticular bleeding occurs commonly as a complication of diverticulosis, it does not frequently coexist with diverticulitis. ^[25]
• Pylephlebitis: Most commonly affecting the superior mesenteric vein, portal vein, and inferior mesenteric vein ^[20]

Late ^[20]

• Fistulas ^[26]
  • Epidemiology
    • Most commonly colovesical
    • Other forms: colovaginal, coloenteric, colocutaneous
  • Clinical findings
    • Pneumaturia and fecaluria
    • May cause recurring urinary tract infections, including urosepsis
  • Diagnosis: CT with oral contrast
    • Localized thickening of the colon and bladder
    • Air or contrast material in the bladder
  • Treatment
    • Resection and primary anastomosis
    • Antibiotics if surgery is not possible
• Recurrent diverticulitis ^[5]
  • ∼ 13–23% of patients with uncomplicated diverticulitis ^[6]
  • Up to 40% of patients with complicated diverticulitis
  • Refer patients with recurrence risk factors for specialist consultation to discuss long-term preventative therapy. ^[6]
• Colon cancer: possibly increased short-term risk following an episode of acute diverticulitis. ^[9][27]

We list the most important complications. The selection is not exhaustive.

• One-Minute Telegram 74-2023-2/3: Respect the decision to resect
• One-Minute Telegram 44-2022-1/3: The ACP’s new diverticulitis guidelines
• One-Minute Telegram 21-2021-2/3: Amoxicillin-clavulanate: An alternative to fluoroquinolones in treating diverticulitis?

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