What is the best imaging modality for diagnosing diverticulitis?

Best Imaging for Diverticulitis

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

Imaging Options for Diverticulitis

CT Scan (First-Line)

• Sensitivity: 92-99%

• Specificity: 97-100% 1

• Key advantages:

  • Most accurate diagnostic tool for diverticulitis
  • Can identify complications (perforation, abscess, pylephlebitis, bowel obstruction, bleeding, fistula)
  • Can rule out alternative diagnoses
  • Reduces hospital admissions by >50% and shortens hospital stays 1
  • Predicts recurrence risk based on colonic wall thickness 1

• Contrast considerations:

  • IV contrast is usually appropriate and helps detect subtle bowel wall abnormalities 1
  • Non-contrast CT is still accurate when IV contrast is contraindicated 1
  • Radiation dose-reduced CT (50-90% less than standard) maintains similar accuracy 1

Alternative Imaging (When CT is unavailable/contraindicated)

Ultrasound (US)

• Sensitivity: 61-100% (in patients with abdominal pain) 1
• Specificity: 99-100% (in patients with abdominal pain) 1
• Diagnostic criteria:
  • Short-segment colonic wall thickening (>5 mm)
  • Inflamed diverticulum in thickened area
  • Noncompressible hyperechoic pericolic tissue 1
• Limitations:
  • Less accurate in obese patients
  • Limited in patients with distal sigmoid diverticulitis
  • Requires higher level of operator training
  • May be limited by abdominal tenderness 1

MRI

• Sensitivity: 94% (95% CI: 82-99%)
• Specificity: 88% (95% CI: 47-100%) 1
• Limitations:
  • Less readily available than CT
  • More affected by patient motion
  • Less studied for diverticulitis diagnosis 1
  • May cause distress for patients with noise sensitivity or claustrophobia 1

Special Populations

Pregnant Patients

• Either US or MRI can be considered for imaging
• Current evidence insufficient to recommend one over the other 1
• CT should be avoided due to radiation exposure concerns

Clinical Impact of Imaging Choice

The severity of diverticulitis on CT is predictive of:

• Risk of medical treatment failure during acute phase
• Chances of poor outcomes after successful medical treatment 2

Common Pitfalls and Caveats

1. Misdiagnosis: CT helps differentiate diverticulitis from colon cancer, which can present similarly. Key CT findings favoring diverticulitis include:

   • Presence of non-inflamed diverticula
   • Inflamed diverticula
   • Mild degree of enhancement
   • Small lymph node size 3

2. Underestimating severity: Contrast enema significantly underestimates the severity of diverticulitis compared to CT, particularly in detecting abscesses (only 29% of abscesses seen on CT are detected by contrast enema) 4, 2

3. Radiation concerns: While CT is the most accurate test, radiation exposure is a legitimate concern. Consider radiation dose-reduced protocols when appropriate 1

4. Contrast reactions: Be aware of potential contrast-associated side effects, including contrast-induced nephropathy 1

5. Plain radiography: Not useful as initial imaging for suspected diverticulitis due to low sensitivity and specificity compared to CT 1