ANATOMIC VARIATIONS OF INTRAHEPATIC BILIARY SYSTEM AT MAGNETIC RESONANCE CHOLANGIO-PANCREATOGRAPHY: A SINGLE INSTITUTION EXPERIENCE AND A SYSTEMATIC REVIEW OF THE LITERATURE

The twofold purpose of this study was firstly to analyse the imaging features of various anatomical variants of the intra-hepatic biliary tree using magnetic resonance cholangio-pancreatography (MRCP) and to document the prevalence of each type in our population. The second aim was to perform a systematic review in order to evaluate the prevalence of anatomic variations of the intrahepatic biliary system in different studies and with different imaging methods. Patients who underwent MRCP between January 2009 and December 2011 were included and analyzed. All examinations were obtained using 1.5 Tesla MRI and 8 channel phased-array coil. In order to compare data coming from the present study and different series published by other authors, a comprehensive literature search using the MEDLINE and Pubmed databases was performed, covering the period from January 1980 to December 2017. Among 534 patients, normal morphology of the intrahepatic biliary system (Type 1) was found in 55% of cases. The second most frequent presentation, in about 19.8% of patients, was Type 3a with right posterior duct (RPD) emptying into the left hepatic duct. Triple confluence morphology (Type 2) was found in 10.1% of cases; only 6.7% of patients presented with Type 3b variant with aberrant RPD draining into the common hepatic duct. In about 8.4% of cases, more complex biliary variants were found. At the time of this review, thirty studies employing different imaging methods were identified in the literature search, of which fifteen used MRCP, eleven used intra-operative cholangiography, three used CT-cholangiography and one ERCP. Taking into account all of the studies, the total number of patients was 14,322. Type 1 presentation ranged from 40% to 80%. A correct understanding of the biliary three anatomy through MRCP study is feasible and it may be very useful in order to plan complex hepatobiliary surgeries and to prevent iatrogenic injuries