Which imaging study is appropriate to evaluate for abdominal metastases in suspected colorectal cancer after colonoscopy-detected adenocarcinoma?

• A. PET scan
• B. Chest X-ray
• C. MRI brain
• D. CT scan of the abdomen

Answer: (D)

The key idea is how to stage colorectal cancer by looking for spread beyond the colon, with attention to the liver as the most common site of metastasis. A CT scan of the abdomen (often with IV contrast and includes the pelvis) is the best initial imaging test for this purpose. It provides detailed cross‑sectional images of the liver, peritoneum, and regional lymph nodes, allowing detection of liver metastases and assessment of disease extent to guide treatment planning or surgical decisions.

Other options aren’t as suitable for evaluating abdominal metastases first. A PET scan can detect metabolically active disease but is usually used when CT findings are inconclusive or for restaging, not as the first-line test for abdominal metastases. A chest X-ray mainly screens the thorax and is less sensitive for liver metastases. MRI of the brain isn’t relevant unless there are neurologic symptoms, since the question focuses on abdominal spread.