Diverticulitis occurs when there is inflammation of diverticula, the abnormal outpouchings of the colonic wall. Graser first described diverticulitis in 1899. Left-sided diverticulitis is most common in the Western world and is the focus of this page.


  • Risk factors: Western diets high in red meat, fat, and refined grains, central obesity, smoking
  • Protective factors: increased fiber intake, physical activity


  • Diverticulitis occurs in a small percentage of people with diverticulosis


  • Obstruction of the orifice of a diverticulum, leading to stasis, bacterial overgrowth, inflammation, and increased pressure causing ischemia and microperforation


  • Anorexia
  • Nausea
  • Urinary urgency (if bladder is secondarily inflamed)

Physical exam

  • Fever
  • Vomiting
  • LLQ abdominal pain with localized tenderness
  • Abdominal distention
  • Change in bowel habits → diarrhea (35%) or constipation (50%)
  • Rectal bleeding is rare → consider IBD or ischemic colitis if present


  • Leukocytosis
  • Elevated ESR 
  • Elevated CRP: may be indicative of complicated diverticulitis
  • Procalcitonin
  • Fecal calprotectin: maybe associated with diverticulitis recurrence


  • Flat and upright plain films
    • Diagnose obstruction or free intraperitoneal air
    • Nonspecific  
  • CT abdomen and pelvis with water-soluble PO or rectal contrast and IV contrast
    • Best initial imaging for suspected diverticulitis (even without contrast)
    • Best for confirming diagnosis, excluding others, and classifying severity
    • Can stratify patients according to Hinchey classification
    • Findings: diverticula, colonic wall thickening, pericolic fat stranding, abscess formation
  • US, and MRI can be used for initial evaluation of suspected acute diverticulitis if CT is unavailable or contraindicated
  • Flexible endoscopy during acute diverticulitis should be used with caution, as perforation is a risk.


  • Inpatient management
    • If patient is unable to tolerate oral intake, excessively vomiting, showing signs of peritonitis, immunocompromised, at an advanced age
    • IV antibiotics (Gram-negative rods and anaerobes for 3 – 5 days) before switching to PO antibiotics (for 10 – 14 days)
      • Antibiotics are appropriate for high-risk patients with significant comorbid conditions, signs of systemic infection, or immunocompromised status
      • Nonoperative treatment of diverticulitis may include antibiotics
      • Select patients with uncomplicated diverticulitis can be treated without antibiotics
    • IVF
    • Pain management
    • Bowel rest
    • Goal: defervescence and improvement in leukocytosis for 2 – 4 days. If not, alternative diagnoses or complications should be suspected. Surgical evaluation should be considered.
    • Surgery
      • Reserved for significant complications, if there is an inability to exclude malignancy, or in those who fail nonoperative treatment
      • Restoring bowel continuity after resection should incorporate patient factors, intraoperative factors, and surgeon preference
  • Outpatient management
    • Bowel rest
    • Increased fluid intake
    • PO antibiotics (single or multiple drug regimen for Gram-negative rods and anaerobics), usually quinolones or sulfa drugs + metronidazole OR single agent amoxicillin-clavulanate
  • Abscesses
    • Abscesses > 3 cm: image-guided percutaneous drainage in stable patients
    • Abscesses < 3 cm
      • Antibiotics alone
        • Can be outpatient if patient is stable
        • If antibiotics alone fail, percutaneous drainage is considered
      • Antibiotics plus percutaneous drainage
  • Elective surgery
    • Elective colonic resection is considered after successful nonoperative treatment of diverticular abscess because the recurrence rate of diverticulitis is substantial, especially with history of diverticular abscess.
    • Elective colectomy is typically recommended for patients with diverticulitis complicated by fistula, obstruction, or stricture. 
    • Elective sigmoid colectomy should be individualized in patients who have recovered from uncomplicated acute diverticulitis. 
  • Follow-up colonoscopy is recommended 6 weeks after resolution of symptoms in order to rule out malignancy and IBD, if it was not performed recently.
    • Data suggesting follow up be conducted at 6 weeks is weak
    • CT findings suggesting occult malignancy: abscess, shouldering (leading edges of mass have a shelf-like appearance), obstruction, mesenteric or retroperitoneal lymphadenopathy

Relevant Information

  • Nuts, seeds, and popcorn are NOT associated with increased risk of diverticulosis, diverticulitis, or diverticular bleeding
  • Diverticula
    • Saccular outpouchings of the bowel wall
    • True diverticula
      • Contain all layers of the bowel wall
      • Rare, usually congenital
    • False diverticula
      • Contain only mucosa and muscularis mucosa layers of the bowel wall
  • Common incidental finding on routine colonoscopy
  • Right-sided diverticulitis is common in Asian countries. It usually affects younger patients and can be difficult to differentiate from acute appendicitis, among other diagnoses


  • Abscess formation → most common complication
  • Fistula (colovesicular fistula is most common)
  • Partial bowel obstruction or pseudo-obstruction
  • Peritonitis
  • Sepsis

Classification System

  • CT scan has a limited ability to distinguish between Grade 3 and Grade 4 → accurate diagnosis is made in the OR

Differential Diagnoses

  • Ischemic colitis
  • IBD
  • Chronic mesenteric ischemia
  • Constipation
  • Colovesicular fistula
  • Intestinal perforation
  • Irritable bowel syndrome
  • Large bowel obstruction