CT cholangiography
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) was unable to be performed due to extensive inflammation or a narrow cystic duct, proving direct cannulation difficult.
Contraindications
- bilirubin should be < 30 mmol/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 hypersensitivity or allergy
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
