Computed Tomography (CT) Scan is the Diagnostic Test of Choice for Suspected Acute Sigmoid Diverticulitis
The diagnostic test of choice for suspected acute sigmoid diverticulitis is computed tomography (CT) scan of the abdomen and pelvis (option c). This recommendation is strongly supported by the American College of Radiology due to CT's superior diagnostic accuracy and ability to detect complications 1.
Why CT is Superior
CT demonstrates exceptional diagnostic performance for acute diverticulitis with:
- Sensitivity of 94-99%
- Specificity of 96-99%
- Overall accuracy of 98% 1
These metrics significantly outperform other imaging modalities, making CT the clear first-line choice. Early studies comparing CT with barium enema found CT had a sensitivity of 93% compared to only 80% for barium enema studies 2.
Advantages of CT Over Alternative Options
CT vs. Barium/Gastrografin Enema (options a and b)
- Barium enema is contraindicated in acute diverticulitis due to risk of barium peritonitis if perforation is present 1
- Gastrografin (water-soluble contrast) enema has lower sensitivity (71.6%) and accuracy (71.3%) compared to CT (97.5% sensitivity, 97.1% accuracy) 3
- CT can identify extracolonic pathology that contrast studies cannot detect 2
CT vs. Ultrasound (option d)
- While ultrasound has reasonable sensitivity and specificity (~90%), it has significant limitations:
- Less reliable in obese patients
- Less accurate for distal sigmoid diverticulitis
- Operator-dependent 1
CT vs. Colonoscopy (option e)
- Colonoscopy is contraindicated in acute diverticulitis due to risk of perforation 4
- Should be reserved for follow-up after resolution of acute symptoms to rule out malignancy 4
Clinical Impact of CT
CT not only confirms the diagnosis but also:
- Stratifies disease severity by identifying complications (abscess, fistula, obstruction, perforation)
- Guides appropriate management decisions between conservative treatment and surgery 5
- Identifies alternative diagnoses in patients with suspected diverticulitis
- Enables CT-guided percutaneous drainage of abscesses when needed 5
Technical Considerations
For optimal CT performance:
- IV contrast enhancement is recommended to improve detection of subtle bowel wall abnormalities 1
- Low-dose techniques can reduce radiation exposure by 75-90% while maintaining diagnostic accuracy 1
Special Situations
In select cases where CT may not be immediately available or contraindicated:
- Ultrasound may serve as an alternative first-line test, particularly in young patients to reduce radiation exposure 1, 6
- MRI offers good sensitivity (94%) and specificity (88%) but is limited by longer acquisition times and motion artifacts 1
In summary, CT scan of the abdomen and pelvis represents the gold standard for diagnosing acute sigmoid diverticulitis due to its superior diagnostic accuracy, ability to detect complications, and capacity to identify alternative diagnoses.