Evaluation of anatomic variatons of the biliary system with MRCP

The biliary tract is divided into two; intrahepatic and extrahepatic bile ducts. Besides the defined normal anatomical pattern, biliary ducts also show intra and extrahepatic variations. These variations pose a risk for iatrogenic injuries in laparoscopic and laparotomic cholecystectomy, as well as in hepatic resection and live donor liver transplantation surgery. Therefore, knowledge of the anatomy and variations of the biliary tree is important for surgery. Besides that, variations of the biliary tract are known to predispose to calculus formation, recurring pancreatitis, cholangitis and biliary malignancies. Our purpose in this study is to determine the frequency of anatomical variations of the biliary system with MRCP, and assess diagnostic value of MRCP in this context. In this retrospective study, 364 patients that were referred to our MRI unit between January 2011 and March 2014 were evaluated. 160 patients had examinations, while sufficient to evaluate for the pathology for which they were performed, not suitable for variation screening, and were excluded. Out of the 204 cases of ages between 19 and 98 (mean 49.2) included in the study, 29 were examined by using a 3 T MRI scanner (Siemens Magnetom Spectra) and the remaining 175 by using a 1.5 T MRI scanner (Siemens Magnetom Avanto). Heavily T2W and reformat MIP images aquired from the scanners were evaluated. Out of 204 cases included in the study, 91 (44.6%) demonstrated variations. Some cases showed more than one variation. 1 case had 3 variations, 20 cases had 2 and 70 cases had 1. Total number of variations was found to be 113. 3 cases (1.5%) had quadrifurcation, 21 cases (10.2%) trifurcation, 13 cases (6.3%) aberrant right posterior (opening into the main hepatic duct proximal to the cystic duct), 23 cases (11.2%) right posterior segment branch joining left hepatic duct, 1 case (0.5%) duplication variant (gallbladder uniting with right hepatic ductus and joining the left hepatic duct proximal to ampulla), 5 cases (2.4%) long cystic duct, 1 case (0.5%) short cystic duct, 23 cases (11.2%) joining from medial, 9 cases (4.4%) joining from medial distally, 4 cases (2%) pancreatic divisum, 8 cases (4%) vascular compression on the common hepatic duct, 1 case (0.5%) high localization of gallbladder and 1 case (0.5%) transverse positioned gallbladder. MRCP, is a useful, fast, reproducible and noninvasive method for examination of biliary anatomy and variations. Demonstration of these anatomic variations prior to surgery can prevent possible iatrogenic traumas