Role of CT Scan in Diagnosing and Treating Diverticulitis
CT scan with intravenous contrast is the recommended initial imaging modality for diagnosing suspected acute diverticulitis due to its high diagnostic accuracy of 98% and ability to detect complications that influence treatment decisions. 1
Diagnostic Value of CT in Diverticulitis
- CT abdomen and pelvis is the imaging examination of choice for evaluating patients with suspected diverticulitis, offering superior diagnostic accuracy, reproducibility, and the ability to identify alternative diagnoses 1
- CT helps confirm the diagnosis of diverticulitis, evaluate disease extent, detect complications, and guide appropriate treatment decisions 1, 2
- Misdiagnosis based on clinical assessment alone occurs in 34-68% of cases, making imaging crucial for accurate diagnosis 1
- Early CT diagnosis can reduce hospital admission by more than 50% and shorten hospital length of stay 1, 2
Optimal CT Protocol
- IV contrast significantly improves characterization and detection of subtle bowel wall abnormalities and complications such as abscesses, fistulas, and perforations 1, 2
- While IV contrast is preferred, CT without IV contrast is still more accurate than clinical evaluation alone and can be used in patients with contraindications to contrast material 1, 3
- Oral contrast is generally not necessary for most patients with suspected diverticulitis 2
- Low-dose CT techniques can achieve radiation dose reduction of 75-90% compared to standard-dose CT while maintaining similar sensitivity and specificity 1
Key CT Findings in Diverticulitis
- Colonic wall thickening (>5mm) in the affected segment, most commonly in the sigmoid colon 3
- Pericolonic fat stranding adjacent to the inflamed diverticulum 3
- Presence of diverticula with a thickened diverticulum at the epicenter of inflammatory changes 3
- Extraluminal gas indicating perforation 3
- Pericolic abscess appearing as rim-enhancing fluid collection adjacent to affected bowel 3
- Fascial thickening in the affected area 3
CT for Disease Stratification and Treatment Planning
- CT findings help stratify patients for operative versus non-operative treatment 1
- CT assists in determining inpatient versus outpatient management 1
- CT can identify complications requiring specific interventions:
- CT may predict recurrence risk, with colonic wall thickness <9 mm associated with a 19% recurrence risk 1
Alternative Imaging When CT is Unavailable or Contraindicated
- If CT is unavailable or contraindicated, ultrasound (US) or magnetic resonance imaging (MRI) are suggested as alternative diagnostic modalities 1
- US has the advantage of being real-time, noninvasive, and can be directed to the area of maximal pain 1
- MRI shows promising diagnostic potential with reported sensitivity of 86-94% and specificity of 88-92%, though motion artifacts may limit image quality in acutely ill patients 1
- In pregnant patients, US or MRI should be considered instead of CT to avoid radiation exposure 1
Common Pitfalls to Avoid
- Relying solely on clinical assessment without imaging can lead to high misdiagnosis rates 1, 2
- Underestimating the value of IV contrast can result in lower sensitivity for detecting inflammation and complications 2
- Delaying imaging can lead to increased hospital admission rates and longer hospital stays 1, 2
- Small diverticula may be missed if the bowel is not adequately distended 3
- Distal sigmoid diverticulitis may be more difficult to visualize due to its pelvic location 3
Special Considerations
- For patients who cannot receive IV contrast, non-contrast CT remains diagnostically valuable 3
- In elderly patients, CT with IV contrast is particularly important as clinical presentation may be atypical 2
- Colonoscopy should not be performed during an acute flare-up but should be considered six weeks after symptom resolution in patients with complicated diverticulitis who haven't had a recent high-quality colonoscopy 4