MRCP is short form of Magnetic Resonance Cholangio-Pancreatography. The investigation is a type of MRI. It evaluates gall bladder, biliary tree (e.g. CBD, CHD, RHD, LHD & IHBR), pancreas and pancreatic duct (MPD). Most of the gall bladder (and biliary tree) stones are radio-lucent, i.e. they can not obstruct the x-rays (or x-rays can pass through the stones). So they are not visible on either x-ray or CT scan. USG (sonography) can show gall bladder stones, but these stones are not appreciated on CT scan. So when patient is asked to undergo cholecystectomy (removal of gall bladder), he / she is advised for MRCP.
What are the advantages of MRCP over CT scan or USG?
(1) MRCP works on principle of magnetism. So there is no risk of radiation or complications related to radiation. Even pregnant lady can undergo MRCP investigation without fear of radiation to the fetus.
(2) Almost all stones are appreciated on MRCP. So if there is any small stone in CBD, which is not appreciated on USG, then it is appreciated on MRCP and it can be removed before going for cholecystectomy. Because later on this unattended stone may cause jaundice.
(3) MRCP will give idea about anatomy of biliary tree in a patient. This is the most important information that we can get from MRCP and neither from CT scan nor USG. Few patients have slightly different anatomy of biliary tree and it is very much essential for a surgeon to know anatomy of biliary tree. Because, if during surgery, unknowingly biliary duct is injured due to different anatomy, it can lead to biliary leak and it is one of the complications of cholecystectomy surgery.