Diverticulitis

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.

Etiology

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

Epidemiology

• Diverticulitis occurs in a small percentage of people with diverticulosis

Pathogenesis

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

History

• 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

Labs

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

Imaging

• 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.

Treatment

• 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

Complications

• 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

Resources

• American Society of Colon and Rectal Surgeons. “Clinical Practice Guidelines for the Treatment of Left-Sided Colonic Diverticulitis,” (2020)