Biliary imaging

Ultrasound

• Initial study of choice
• Gallstones - echogenic focus with characteristic shadowing. Differentiate from polyps by moving the patient.
• Sludge moves more slowly and does not have the sharp echogenic pattern of gallstones
• Cholesterolosis - accumulation of cholesterol in GB mucosal macrophages

HIDA scan (Hepatic IminoDiacetic Acid)

• Doesn't provide anatomic information or see gallstones, but evaluates the physiologic secretion of bile
• Iminodiacetic acid is processed in the liver and secreted with bile
• Failure to fill the GB two hours after injection indicates obstruction of the cystic duct (acute cholecystitis)
• Will also identify CBD obstruction and bile leaks
• Administration of a fatty meal/injection of CCK during the scan can be used to identify biliary dyskinesia - an ejection fraction of <35-40% is considered abnormal, but not diagnostic. False positives can be seen in diabetes, obesity, cirrhosis, etc. Re-image about 45 minutes after fatty meal to calculate EF.

Normal study:

Acute cholecystitis (no GB filling):

GB dyskinesia (no emptying of GB):

CT

• Most gallstones are radiographically isodense to bile

MRCP (magnetic resonance cholangiopancreatography)

• Uses the water in bile to delineate the biliary tree

ERCP

• See topic under endoscopy

PTC (percutaneous trans-hepatic cholangiography)

• Needle passed directly into the liver to access one of the biliary radicals
• Catheters can be directly inserted for drainage/biopsy