Gastrointestinal and Hepatobiliary Radiology
Gastrointestinal and Hepatobiliary Radiology
This domain tests liver lesion characterization, biliary obstruction, pancreatic disease, and acute bowel pathology. LI-RADS and complication recognition are high-yield.
Core rules
- LI-RADS in cirrhosis: arterial phase hyperenhancement plus washout and/or capsule, with size ≥10 mm, gives LR-5 (definite HCC). LR-4 is probable HCC; LR-M includes cholangiocarcinoma and other malignancies.
- Hemangioma: peripheral nodular enhancement with centripetal fill-in and no washout. Focal nodular hyperplasia: arterial enhancement, central scar, and persistent delayed enhancement.
- Biliary obstruction: dilated intra- and extrahepatic ducts; the level is shown by duct cutoff. Choledocholithiasis is usually a filling defect on MRCP or CT.
- Acute pancreatitis: interstitial edematous versus necrotizing; look for pseudocyst, walled-off necrosis, and vascular complications.
Worked example
A 58-year-old with cirrhosis has a 2.5 cm lesion. It shows arterial hyperenhancement, portal venous washout, and a thin enhancing capsule. These are LI-RADS major features; the lesion is LR-5, so HCC can be diagnosed without biopsy in a high-risk patient. If it instead showed peripheral rim enhancement and targetoid appearance, LR-M would prompt biopsy.
Traps
Calling hemangioma malignant because of nodular enhancement; forgetting that FNH does not wash out; missing pneumatosis or portal venous gas in bowel ischemia; mislabeling a dilated bile duct as a cyst; ignoring that LI-RADS applies only in cirrhosis or chronic hepatitis B.