Gastrointestinal and Abdominal Imaging
Gastrointestinal and Abdominal Imaging tests acute abdominal CT, liver lesion characterisation, biliary and pancreatic disease and the use of multiphase protocols.
Acute abdomen
Appendicitis: appendix over 6 mm, wall thickening, fat stranding, appendicolith. Diverticulitis: pericolic fat stranding with a diverticulum, often sigmoid. Small bowel obstruction: dilated loops over 3 cm with a transition point; large bowel over 6 cm. Perforation: free intraperitoneal air, best seen on lung windows. Ischaemia: pneumatosis, portal venous gas, absent enhancement.
Liver
LI-RADS 5 in a cirrhotic patient requires arterial phase hyperenhancement plus washout, capsule or threshold growth, with size at least 10 mm; this is diagnostic of hepatocellular carcinoma and needs no biopsy. Haemangiomas show peripheral nodular enhancement with centripetal fill-in; metastases are typically hypovascular with ring enhancement.
Biliary and pancreas
Ultrasound is first line for gallstones; MRCP for ductal anatomy. Pancreatic duct dilation with a double-duct sign suggests a pancreatic head tumour.
Worked example
A 60-year-old with hepatitis C cirrhosis has a 22 mm segment VII lesion with arterial hyperenhancement, portal venous washout and a capsule. This meets LI-RADS 5 because all three major features are present and size exceeds 10 mm; the correct next step is multidisciplinary discussion for curative treatment, not biopsy.
Traps
Using single-phase CT for liver lesions; misclassifying a haemangioma as hepatocellular carcinoma because of enhancement; forgetting that LI-RADS applies only to at-risk patients; calling dilated bowel obstruction without a transition point.