What is the recommended imaging study and treatment for suspected diverticulitis, particularly when considering CT contrast?

CT Imaging for Suspected Diverticulitis

For patients with suspected diverticulitis, CT abdomen and pelvis with IV contrast is the recommended initial imaging modality due to its high diagnostic accuracy (98%) and ability to detect complications that impact treatment decisions. 1, 2

Optimal CT Protocol for Diverticulitis

• CT with IV contrast is the preferred imaging modality for suspected diverticulitis as it improves characterization and detection of subtle bowel wall abnormalities and complications such as diverticular abscess 1
• While IV contrast is usually appropriate, CT without IV contrast may still be appropriate in patients with contraindications to contrast and remains more accurate than clinical evaluation alone 1, 3
• CT findings in diverticulitis include colonic wall thickening (>5mm), pericolonic fat stranding, inflamed diverticula, and potential complications like abscess or extraluminal air 2
• Early CT imaging can reduce hospital admission rates by more than 50% and shorten hospital length of stay by enabling appropriate triage decisions 3, 4

Alternative Imaging Modalities

• If CT is unavailable or contraindicated, ultrasound or MRI are reasonable alternatives 1
• Ultrasound has reported sensitivities of 61-100% and specificities of 99-100% for diverticulitis, though results may be limited by abdominal tenderness or patient obesity 1, 3
• MRI shows promising diagnostic potential with sensitivity of 94% and specificity of 88%, but may be limited by availability, cost, and patient factors such as claustrophobia 1
• For pregnant patients with suspected diverticulitis, ultrasound or MRI should be considered as initial imaging options to avoid radiation exposure 1

Clinical Impact of CT Findings

• CT findings help stratify patients for operative versus non-operative treatment, with severe findings on CT predicting higher risk of medical treatment failure (26% vs 4% for moderate findings) 1, 2, 5
• CT accurately identifies complications requiring intervention, such as abscesses ≥3 cm that need percutaneous drainage 2, 6, 4
• The severity of diverticulitis on CT is predictive of both acute treatment failure and long-term outcomes 2, 5
• CT can identify alternative diagnoses in patients with left lower quadrant pain, avoiding misdiagnosis rates of 34-68% that occur with clinical assessment alone 3, 4

Treatment Approach Based on CT Findings

• Uncomplicated diverticulitis (localized inflammation without abscess, perforation, or peritonitis) can typically be managed as an outpatient with selective use of antibiotics 6
• Small abscesses can be managed with bowel rest and antibiotics, while abscesses 3-5 cm should be drained percutaneously 6, 4
• Peritonitis or sepsis requires fluid resuscitation, antibiotics, and urgent surgical intervention 6
• Follow-up colonoscopy is recommended for all patients with complicated diverticulitis approximately 6 weeks after CT diagnosis 6

Common Pitfalls to Avoid

• Relying solely on clinical assessment without imaging can lead to misdiagnosis and inappropriate treatment 3, 5
• Underestimating the value of IV contrast can result in lower sensitivity for detecting inflammation and complications 2, 3
• Small diverticula may be missed if the bowel is not adequately distended 2
• Distal sigmoid diverticulitis may be more difficult to visualize due to its pelvic location 2