Cholangiography is an examination that uses X-rays and contrast medium (dye) to view your bile ducts. It is often used to see if the bile ducts are blocked, such as in obstructive jaundice, where the bile is blocked from flowing into the duodenum and spills into the blood. Obstructive jaundice can be caused by gallstones blocking the bile ducts.
In the procedure, the contrast medium is injected into the body and a series of X-rays taken to reveal any gallstones, other obstructions or narrowing in the bile ducts.
Several techniques can be used to introduce the dye into the body.
Percutaneous transhepatic cholangiography (PTC)
The dye is injected through the skin into the bile ducts within the liver (intrahepatic biliary ducts). This is done using ultrasound to guide where the needle goes.
The dye is injected directly into the bile duct during a gallbladder operation.
Endoscopic retrograde cholangiopancreatography (ERCP)
The dye is injected into the common bile duct and the pancreatic duct through a catheter that’s passed down an endoscope. The endoscope is a thin, flexible lighted tube that is gently passed down your throat and through your stomach, until it reaches the duodenum.
Irrespective of how it is introduced, once the dye is in the bile ducts, it can spread into the whole biliary drainage system. Then X-rays can be taken to show up any narrowing or blockages in the drainage system. The resulting radiographic record is called a cholangiogram.
Magnetic resonance cholangiopancreatography (MRCP)
Magnetic resonance cholangiopancreatography (MRCP) is a relatively new technique for viewing the bile ducts, the pancreatic duct and the gallbladder. No contrast medium has to be administered for MRCP, unlike the other techniques mentioned here. MRCP uses magnetic resonance imaging (MRI) to produce detailed pictures.
Magnetic resonance imaging uses radiofrequency waves directed at the body (you do not feel anything) to excite hydrogen atoms in the molecules of water in your body. This is done in a strong magnetic field, which causes the nuclei of your hydrogen atoms to align. These nuclei emit radio signals when they return to their natural alignment. The signals are used to build up a computerised image that shows differences in body tissues based on the amount of water in them. This enables extremely clear and detailed pictures to be obtained of the bile ducts and pancreatic ducts.
MRCP is an outpatient procedure that involves lying very still in an MRI scanner for several minutes at a time. The entire experience should be over in less than 20 minutes. There is no exposure to radiation, but MRCP is not suitable for people with some types of metal objects in their body — ask the centre performing the test for more details.
MRCP is very safe and effective, with images comparable to ERCP. However, ERCP has the added advantage that therapeutic procedures can be performed at the same time. All these things will be taken into account when deciding which test to order.