Can Non-Contrast CT Detect Non-Inflamed Diverticula?
Yes, non-contrast CT can visualize non-inflamed colonic diverticula as outpouchings of the bowel wall, though this is not the primary clinical indication for non-contrast imaging. 1
Direct Evidence from Imaging Studies
The 2024 ACG and Society of Abdominal Radiology consensus guidelines demonstrate that diverticula themselves are visible on non-contrast CT, as shown in their published case example where a diverticulum in the transverse colon was clearly identified on the non-contrast phase (arrow in Figure 3A) before any contrast administration. 1
Multiple studies confirm that diverticula are detectable on CT in 84% of diverticulitis cases, and these structural outpouchings would be visible regardless of whether inflammation is present. 2
What Non-Contrast CT Actually Shows
Non-contrast CT visualizes diverticula as:
- Outpouchings of the colonic wall extending beyond the normal bowel contour 1
- Air-filled or fluid-filled sacs protruding from the colon 2
- Structural anatomic features that don't require contrast enhancement to be seen 1
Critical Limitations You Must Understand
Non-contrast CT cannot assess for inflammation or complications, which is the clinically relevant question in most scenarios:
- Cannot detect inflammatory changes: Active inflammation requires IV contrast to visualize mural enhancement, hyperemia, and inflammatory changes 3, 4
- Misses early diverticulitis: Wall thickening and pericolic fat stranding are poorly assessed without contrast 3
- Significantly lower sensitivity for complications: Abscess and perforation detection sensitivities are 15-17% lower on non-contrast CT compared to contrast-enhanced CT 5
Clinical Context Matters
For asymptomatic older adults with incidental diverticula (diverticulosis):
- Non-contrast CT will show the diverticula as anatomic structures 1, 2
- However, there is no clinical indication to order CT imaging solely to detect non-inflamed diverticula 1
- Colonoscopy remains the standard for evaluating colonic anatomy when clinically indicated 1
If you're evaluating for diverticular disease complications:
- Always use IV contrast unless absolutely contraindicated 1, 3, 4
- The ACR Appropriateness Criteria designate CT abdomen/pelvis with IV contrast as the examination of choice for suspected diverticulitis 1
- Non-contrast CT has "poorer performance" and should not be relied upon for evaluating inflammatory conditions 3
Common Pitfall to Avoid
Do not confuse "can see diverticula" with "adequate diagnostic study"—while the anatomic outpouchings are visible, non-contrast CT provides no information about the clinically critical question of whether inflammation, microperforation, abscess, or other complications are present. 3, 4, 5