What is the best imaging modality for diagnosing diverticulitis (inflammation of the diverticula)?

Best Imaging for Diverticulitis

For non-pregnant adults with suspected acute diverticulitis, abdominal computed tomography (CT) with intravenous contrast is the recommended initial diagnostic imaging modality. 1

Imaging Options by Patient Population

Non-Pregnant Adults

• First-line: CT abdomen and pelvis with IV contrast

  • Sensitivity: 92-99%
  • Specificity: 97-100% 1
  • Provides excellent visualization of colonic wall thickening, inflamed diverticula, and pericolic inflammation
  • Can identify complications such as abscess, perforation, or fistula formation

• When CT is unavailable or contraindicated:

  • Ultrasound (US) or Magnetic Resonance Imaging (MRI) are acceptable alternatives 1
  • MRI sensitivity: 94%, specificity: 88% 1

Pregnant Patients

• Either ultrasound or MRI can be considered
• No clear recommendation for one over the other due to limited evidence 1

CT Protocol Considerations

• Contrast administration:

  • IV contrast is strongly preferred as it helps characterize and detect subtle bowel wall abnormalities 1
  • Non-contrast CT is an acceptable alternative when IV contrast is contraindicated 2
  • While non-contrast CT is non-inferior for diagnosing diverticulitis itself, it has lower sensitivity for complications (abscess, perforation) 2

• Oral/rectal contrast:

  • Not routinely required for diagnosis of uncomplicated diverticulitis
  • May improve visualization of abscesses by distinguishing them from adjacent bowel 1

Ultrasound Considerations

• More operator-dependent than CT
• Most useful in early, uncomplicated diverticulitis 3
• Diagnostic criteria include:
  1. Short-segment colonic wall thickening (>5 mm)
  2. Inflamed diverticulum in the thickened area
  3. Noncompressible hyperechoic pericolic tissue 1
• Less reliable in obese patients or for distal sigmoid diverticulitis 1
• Requires significant operator experience (estimated 500 examinations for competency) 1

MRI Considerations

• Findings similar to CT: colonic diverticula, thickened diverticulum, and pericolic inflammation
• More affected by patient motion than CT 1
• Less sensitive than CT for detecting extraluminal gas 4
• May be preferred in young patients or those requiring repeated imaging to reduce radiation exposure

Clinical Impact of Imaging Selection

• CT not only confirms diagnosis but also:

  1. Evaluates disease severity and complications
  2. Guides treatment planning (medical vs. surgical management)
  3. Helps identify alternative diagnoses 5
  4. Predicts outcomes - longer segments of involved colon, retroperitoneal abscess, and extraluminal air are associated with recurrence, failure of medical management, and need for surgery 1

• The severity of diverticulitis on CT is statistically predictive of:

  1. Risk of medical treatment failure during acute phase (26% for severe vs. 4% for moderate diverticulitis)
  2. Chances of poor secondary outcomes after successful medical treatment (36% vs. 17%) 6

Common Pitfalls

• Relying on plain radiography, which has very limited utility for diverticulitis diagnosis
• Using ultrasound as first-line imaging in obese patients where visualization is limited
• Failing to use IV contrast when available, which reduces sensitivity for complications
• Not considering alternative diagnoses that may mimic diverticulitis (appendicitis, inflammatory bowel disease, gynecological conditions, colonic malignancy)

CT with IV contrast remains the gold standard for diagnosing diverticulitis, offering superior diagnostic accuracy and the ability to identify complications that may require urgent intervention.