In suspected acute diverticulitis with LLQ pain and mass, which imaging test has the highest sensitivity and specificity for confirming the diagnosis?

• A. Abdominal radiograph
• B. Abdominal ultrasound
• C. CT scan of the abdomen
• D. MRI of the abdomen

Answer: (C)

For suspected acute diverticulitis with left lower quadrant pain and a palpable mass, you want imaging that can confirm inflammation of the diverticula and identify complications. A CT scan of the abdomen with IV contrast provides the highest sensitivity and specificity for this diagnosis. It reliably shows colonic wall thickening, diverticula, and pericolic fat stranding, and it can detect abscesses, phlegmons, perforation, or obstruction. This information not only confirms the diagnosis but also guides management, such as deciding between antibiotics alone versus drainage for an abscess.

Abdominal radiographs offer limited diagnostic value for diverticulitis and are mainly used to assess for complications like obstruction or free air. Ultrasound can detect some features like wall thickening and fat changes but is highly operator-dependent and less reliable, reducing its overall accuracy. MRI provides excellent soft-tissue detail but is not practical in most acute settings due to availability and time; it’s reserved for specific situations (e.g., contrast allergy, pregnancy) rather than routine confirmation.