MRI can be performed with a variety of specific sequences, one of which is a heavily T2-weighted fluid-sensitive 3-D sequence, acquired over 3 to 5 minutes in the coronal plane using respiratory triggering or diaphragmatic gating, which is called MRCP [47]. This sequence uses the intrinsic differential T2 contrast between the fluid in the biliary tree (very high T2 relaxation time) and the remaining organs (much lower T2 relaxation time) to generate a cholangiogram without requiring contrast injection. Source images from a 3-D MRCP sequence have been shown to be useful in depicting the 3-D anatomy of the biliary and pancreatic ducts [48,49]. For detection of ductal calculi, MRI (with or without MRCP sequences) is more sensitive than CT or US [26,34,50-53]. IV contrast administration with MRCP is not necessary in the evaluation of patients with suspected CBD stones; however, IV contrast improves the sensitivity of MRCP for the detection of peribiliary enhancement (a finding in cholangitis, which can complicate an obstructing CBD stone) and improves the confidence in the diagnosis and staging of unsuspected pancreaticobiliary tumors [54-56]. For diagnosis of CBD stones, MRCP (without IV contrast) has a reported sensitivity ranging from 77% to 88%, specificity between 50% to 72%, accuracy of 83%, positive predictive value between 87% to 90%, and negative predictive value between 27% to 72%, as compared to the gold standard of ERCP [57,58]. However, MRCP has diminishing sensitivity with decreasing stone sizes of <4 mm [58-60]. The reasons for the low specificity of MRCP for tiny CBD stones are multifactorial. One such factor is that there is an increased likelihood for spontaneous stone passage when stones are <4 mm in size; therefore, the stone may be present for the MRCP but have passed by the time of the ERCP. Similarly, the sensitivity of MRCP may be affected by stones in the gallbladder that pass into the CBD between the MRCP and the ERCP [60].
Jaundice. MRI can be performed with a variety of specific sequences, one of which is a heavily T2-weighted fluid-sensitive 3-D sequence, acquired over 3 to 5 minutes in the coronal plane using respiratory triggering or diaphragmatic gating, which is called MRCP [47]. This sequence uses the intrinsic differential T2 contrast between the fluid in the biliary tree (very high T2 relaxation time) and the remaining organs (much lower T2 relaxation time) to generate a cholangiogram without requiring contrast injection. Source images from a 3-D MRCP sequence have been shown to be useful in depicting the 3-D anatomy of the biliary and pancreatic ducts [48,49]. For detection of ductal calculi, MRI (with or without MRCP sequences) is more sensitive than CT or US [26,34,50-53]. IV contrast administration with MRCP is not necessary in the evaluation of patients with suspected CBD stones; however, IV contrast improves the sensitivity of MRCP for the detection of peribiliary enhancement (a finding in cholangitis, which can complicate an obstructing CBD stone) and improves the confidence in the diagnosis and staging of unsuspected pancreaticobiliary tumors [54-56]. For diagnosis of CBD stones, MRCP (without IV contrast) has a reported sensitivity ranging from 77% to 88%, specificity between 50% to 72%, accuracy of 83%, positive predictive value between 87% to 90%, and negative predictive value between 27% to 72%, as compared to the gold standard of ERCP [57,58]. However, MRCP has diminishing sensitivity with decreasing stone sizes of <4 mm [58-60]. The reasons for the low specificity of MRCP for tiny CBD stones are multifactorial. One such factor is that there is an increased likelihood for spontaneous stone passage when stones are <4 mm in size; therefore, the stone may be present for the MRCP but have passed by the time of the ERCP. Similarly, the sensitivity of MRCP may be affected by stones in the gallbladder that pass into the CBD between the MRCP and the ERCP [60].