Detection of Diverticulitis on CT Without Contrast

Diagnostic Accuracy of Non-Contrast CT for Diverticulitis

Non-contrast CT is more accurate than clinical evaluation alone for diagnosing diverticulitis and can be used effectively in patients with contraindications to IV contrast material 1, 2
According to the American College of Radiology (ACR) Appropriateness Criteria, unenhanced CT without oral contrast receives a rating of 6 out of 9 (may be appropriate) for suspected diverticulitis, compared to 8 out of 9 (usually appropriate) for contrast-enhanced CT 3

Contrast-enhanced CT is superior for detecting complications of diverticulitis, such as abscesses and perforations, with IV and oral contrast helping to distinguish abscesses from adjacent bowel 1
Unenhanced CT with oral contrast is more accurate than unenhanced CT without any contrast 1
Subtle bowel wall abnormalities may be missed without IV contrast 2

When IV contrast is contraindicated, non-contrast CT remains a viable diagnostic option 2
For patients with suspected complications, contrast-enhanced CT should be strongly preferred when possible 1
The American College of Radiology recommends contrast-enhanced CT as the first-line imaging modality for suspected diverticulitis due to its superior diagnostic accuracy 2
Early CT diagnosis can reduce hospital admission by more than 50% and shorten hospital length of stay 2

Ultrasound may be considered as an alternative when CT with contrast is contraindicated, though it is more operator-dependent and less reliable in obese patients 5
MRI shows promise but is currently considered a second-line imaging examination with insufficient published data to support routine use 1, 2

For patients with suspected uncomplicated diverticulitis and no contraindications to contrast, the American College of Radiology suggests using contrast-enhanced CT 1, 2
For patients with contraindications to IV contrast, non-contrast CT is appropriate and diagnostically valuable 2
For patients with suspected complications, every effort should be made to use contrast-enhanced CT if safely possible 1

The American College of Radiology recommends CT scans for patients with suspected diverticulitis, showing characteristic findings including pericolonic fat stranding, bowel wall thickening, and diverticula with a diagnostic accuracy of 98% 6, 7
Colonic wall thickening (>5 mm) in the affected segment, most commonly in the sigmoid colon, is a key finding in diverticulitis 6, 8
Inflamed diverticulum appears as a thickened diverticulum at the epicenter of inflammatory changes 9
Pericolic abscess is seen as rim-enhancing fluid collection adjacent to the affected bowel segment in approximately 35% of cases 10
Free fluid may be present in the abdomen or pelvis 9
Extraluminal gas is present in uncomplicated or complicated cases, with small-volume pericolic air (<5 cm from affected segment) or distant air (>5 cm) 11
Fascial thickening is present in the affected area 9
Arrowhead sign is an arrowhead-shaped configuration of contrast material at the orifice of the inflamed diverticulum 12

CT can predict which patients are likely to experience recurrent diverticulitis, with colonic wall thickness <9 mm having a 19% recurrence risk 6
CT findings help in risk-stratification for operative versus non-operative treatment 6, 7
CT assists in determining inpatient versus outpatient triage, with early CT reducing hospital admission by more than 50% 13
CT helps identify complications requiring intervention, such as abscesses ≥3 cm requiring catheter drainage 6
Free perforation and peritonitis require surgical intervention 6
Fistulas and strictures can be identified 11

IV contrast improves detection of subtle bowel wall abnormalities and complications like abscesses 13
Unenhanced CT is more accurate than clinical evaluation alone and can be used in patients with contraindications to IV contrast 13
Radiation dose-reduced CT (50%-90% less than standard dose) maintains similar sensitivity and specificity 13

Small diverticula may be missed if bowel is not adequately distended 9
Distal sigmoid diverticulitis may be more difficult to visualize due to its pelvic location 8