Is a CT (Computed Tomography) scan of the abdomen without contrast useful in diagnosing diverticular disease?

CT Scan for Diverticular Disease: Value of Non-Contrast Imaging

CT scan without contrast is not the optimal imaging choice for diagnosing diverticular disease, as IV contrast significantly improves detection of inflammation, complications, and alternative diagnoses. 1

Optimal Imaging for Suspected Diverticular Disease

• CT abdomen and pelvis with IV contrast is the recommended first-line imaging modality for suspected diverticulitis due to its superior diagnostic accuracy (98%) and ability to distinguish complicated from uncomplicated disease 1, 2
• IV contrast significantly enhances detection of:
  • Subtle bowel wall abnormalities
  • Mural enhancement associated with inflammation
  • Complications such as abscess formation, fistulas, and perforation 1, 2
• Early CT imaging can reduce hospital admission rates by more than 50% and shorten hospital length of stay by enabling outpatient management of uncomplicated cases 2

Non-Contrast CT: Limited but Still Useful

• For patients who cannot receive IV contrast (renal impairment, severe allergy), non-contrast CT is still more accurate than clinical evaluation alone 1, 2
• Unenhanced CT can detect:
  • Colonic wall thickening
  • Diverticula
  • Inflammatory changes in pericolic fat
  • Large abscesses
  • Extraluminal air 2, 3
• However, non-contrast CT has reduced sensitivity for detecting subtle inflammation and small abscesses compared to contrast-enhanced studies 1, 2

Alternative Imaging Options

• Ultrasound (transabdominal):
  • Can diagnose diverticulitis with sensitivity of 77-98% and specificity of 80-99% 2
  • Less accurate than CT, especially in obese patients 2
  • May miss up to 80% of complicated diverticulitis cases 2
• MRI:
  • Second-line option with diagnostic potential (sensitivity 86-94%, specificity 88-92%) 2
  • Less sensitive for extraluminal gas than CT 2
  • More affected by motion artifacts, especially in acutely ill patients 2

Clinical Implications and Pitfalls

• Relying solely on clinical assessment can lead to misdiagnosis rates of 34-68% when imaging is not performed 1
• CT findings influence treatment decisions by:
  • Differentiating complicated from uncomplicated diverticulitis
  • Identifying patients who can be managed as outpatients
  • Detecting complications requiring intervention (drainage, surgery) 4
• CT can predict unfavorable outcomes based on findings such as:
  • Longer segments of involved colon
  • Retroperitoneal abscess
  • Extraluminal air
  • Size of abscess and inflamed diverticula 2

Bottom Line for Clinical Practice

• For optimal diagnosis of diverticular disease, CT with IV contrast is strongly preferred 1, 2
• Non-contrast CT is a reasonable alternative when IV contrast is contraindicated, but clinicians should be aware of its limitations in detecting subtle inflammation and complications 2, 1
• Clinical assessment alone is insufficient and imaging-based diagnosis significantly improves patient outcomes 1, 4