CT cholangiography is a technique of imaging the biliary tree with the usage of hepatobiliary excreted contrast. It is useful in delineating biliary anatomy, identifying a bile leak or looking for retained gallstones within the biliary system.

Indications

Second-line test (after ultrasound) when investigating for right upper quadrant pain, obstructive LFTs, etc. It can also be used in the postoperative setting (e.g. post-cholecystectomy) where there is a concern for common bile duct injury or retained gallstones, or where intraoperative cholangiography (IOC) is unable to be performed due to extensive inflammation or a narrow cystic duct, proving direct cannulation difficult.

Purpose

The purpose of CT cholangiography is to identify a filling defect in the biliary tree that represents choledocholithiasis or a contrast leak from the biliary tree in case of injury. 

Contraindications

• bilirubin should be <30 µmol/L nor should it be rising rapidly (as the impaired excretory ability of hepatocytes can affect contrast excretion in bile) 

• severe hepatic or renal dysfunction

• thyroid dysfunction

• iodinated-contrast adverse reactions

Technique

CT cholangiography may be performed with either intravenous or oral cholangiographic contrast agents both of which outline the biliary tree with positive contrast. 

Agents

• meglumine iotroxate (Biliscopin): intravenous CT cholangiography agent

Findings

• choledocholithiasis

• biliary stricture

• bile leak / biloma

• aberrant biliary tree anatomy

• other causes of biliary tree obstruction, e.g. pancreatic head tumors

Alternative examinations

• magnetic resonance cholangiopancreatography (MRCP)

• contrast-enhanced MR cholangiography: with gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid

• endoscopic retrograde cholangiopancreatography (ERCP): carries a 5% risk of post-procedure pancreatitis

• intraoperative cholangiography (IOC): performed during cholecystectomy to allow intraoperative detection of retained gallstones or common bile duct injury

Mimics

• occasionally vicarious contrast material excretion can give opacification of the gallbladder and biliary system