Imaging Services
MRCP of the Biliary System
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Basics: What is an MRCP of the biliary system?
MRCP (Magnetic Resonance Cholangiopancreatogram) is a lengthy term, which simply means evaluating the bile ducts (biliary system) within the liver, outside of the liver (common hepatic and common bile duct), the gallbladder, and the outflow tract of the gallbladder (the cystic duct). In addition, the pancreatic duct is visualized. MRCP is extremely important in visualizing a number of pathologies that affect the biliary system, as well as the gallbladder, liver, and pancreas.
ERCP is an invasive procedure requiring anesthesia that combines endoscopy with the injection of an iodinated contrast agent into the biliary and pancreatic ducts. ERCP allows the physician to obtain small tissue samples, in addition to performing manometry, and stenting if needed; the ampulla can be directly visualized as well. However, ERCP carries a significant risk of complications, including pancreatitis, hemorrhage, and perforation. The complication rate is typically in the 5% to 10% range. In addition, ERCP may be difficult in patients with post-surgical anastomotic complications.
MRCP is a less costly, non-invasive, and sensitive technique for evaluating the biliary and pancreatic ductal systems. In MRCP, multiplanar images are obtained parallel to the orientation of the biliary tree, using an MR sequence that is sensitive to static fluid without the need for exogenous contrast agents. Fluid in the ducts appears bright against the darker tissue. Image post-processing (maximal intensity projection) is used to make multi-dimensional images of the entire biliary tree and the pancreatic ducts. MRCP shows the ducts in their natural, non-distended state and can easily be combined with MRI of the surrounding viscera.
* MRCP is usually obtained at the same time as a contrast MRI of the abdomen is performed.
Diseases Diagnosed by MRCP:
MRCP can diagnose the presence of bile duct obstruction and the level of obstruction in most cases; as a matter of fact, biliary calculi as small as 2 mm can be seen. Primary sclerosing cholangitis can be diagnosed from the multiple irregular strictures seen in the biliary ducts. Benign and malignant causes of biliary dilatation can be differentiated and, as MRI of the abdomen is obtained at the same time, with imaging of the adjacent organs, malignant neoplasms and metastatic disease can be detected and evaluated. MRCP has an advantage over ERCP for the detection of cholangiocarcinoma. There is a risk of serious infection following ERCP. Post-operative bile-duct injuries and anastomotic leaks can be readily detected with MRCP and it is suitable for assessment of the biliary tree after liver transplantation.
In patients with recurrent pancreatitis, MRCP can be performed to look for stones, pancreatic divisum, or strictures. MRCP in conjunction with MRI can be used to evaluate parenchymal changes due to pancreatitis or to detect pancreatic cancer. No patient preparation is required for MRCP but fasting 2-4 hours prior to the examination can be beneficial because it reduces the fluid in the gastric antrum and the duodenum, which may overlie the ducts. The MRCP examination with MRI of the abdomen takes about an hour and IV contrast is usually given for the MRI abdomen portion.
Discussion of images above:
The four images above are combined images from an MRI of the liver, as well as an MRCP. The first, third, and fourth images provide excellent visualization of the liver parenchyma, pancreas, and pancreatic duct. The second image is a 3D rendering of the MRCP. It demonstrates a very unusual finding, that of a duplicated gallbladder (arrow). The remainder of the biliary system is normal.
