MRCP In Diagnosis Of Variations Of Intrahepatic Bile Ducts And Cystic Duct And Clinical Value

ObjectiveTo evaluate the common anatomic variations of intrahepatic bile ducts (IHDs) andcystic duct and their incidences by magnetic resonance cholangiopancreatography (MRCP),to refinement and supplement the international common typing standard, to compare theincidences of IHDs and cystic duct variations, to explore the correlation between thevariations of IHDs and cystic duct and biliary obstructive diseases including cholelithiasisand cholangiocarcinoma.Materials and methods246cases undergoing MRCP were collected in our hospital during January2012toMarch2013, who suffered from pancreatic biliary diseases dubiously. There were137males and109females aging from13to87years old, and the average age was62.2±15.5years old. All cases were confirmed by cholecystectomy or endoscopic retrograde cholang-iopancreatography (ERCP).All subjects were examined with Siemens Avanto1.5T SQ superconductive magneticresonance scanner, using abdominal8-channel phased array surface coil. Subjects wereordered to fast for8hours before the examination. First, coronal T2WI, axial T1WI andaxial T2WI with fat suppression were acquired to position cholangiopancreatographyscanning. Then, MRCP examination was underwent for coronal FSE two-dimensional (2D)data acquisition and HASTE three-dimensional (3D) data acquisition, with respiratorygating, flowing compensation, fat suppression and image presaturation techniques. Thesource images were reconstructed by maximum intensity projection (MIP) technique toacquire3D images.In double-blind cases, the MRCP images were reviewed by two experienced radiol-ogists separately, to analyse the types of IHDs and cystic duct variations and make thediagnoses of diseases. When their opinions were different, they discussed with each otherto reach a consensus. Referring to the typing standard of IHDs variations adopted by Vijay Sharma and Jin Woo Choi, we classified the branching pattern of IHDs in this paper on thebasis of the branching pattern of the right anterior and right posterior segmental duct(RASD and RPSD, respectively), and the presence or absence of the first-order branch ofthe left hepatic duct (LHD) and an accessory hepatic duct. The variations of IHDs weredivided into: The typeⅠ pattern was typical anatomy, that is, the common hepatic duct(CHD) forming by the union of right hepatic duct (RHD) and LHD, with RHD forming bythe union of the RASD draining the right anterior segments (V and VIII), and RPSDdraining the right posterior segments (VI and VII). The typeⅡ pattern was tripleconfluence, that is, the CHD forming by convergence of the RASD, RPSD, and LHD. TheType Ⅲpattern, or anomalous drainage of the RPSD, was subdivided according to thedrainage pattern of the RPSD into types Ⅲ A (the RPSD into the LHD), ⅢB (the RPSDinto the CHD), and ⅢC (the RPSD into the CBD). In the type Ⅳpattern, an accessoryhepatic duct was present. This was subdivided according to the drainage pattern of theaccessory duct into types Ⅳ A (accessory duct to the RHD), ⅣB (accessory duct to CHD)and ⅣC (accessory duct to the LHD). The typeⅤ pattern was one in which segmentalducts from segments II and III drained separately into the RHD or CHD. By observing thelength, morphology, running, the way and site draining into the extrahepatic bile duct, weclassified the branching pattern of cystic duct in this paper, according to the research ofTaoureal and KWon about the variations of cystic duct. The type Ⅰpattern was the highdrain into the bifurcation of LHD and RHD. The typeⅡ pattern was the low drain intoCHD, and the standard was the length ratio of CHD and CBD above1. The Type Ⅲpattern was the prone or supine cystic duct bypassing CHD into the left edge. In the typeⅣ pattern, the cystic duct was parallel with CHD above2cm. The type V pattern (otherspecial types) included short cystic duct (<5mm), the cystic duct with cystiform dilationand negative angle.The data was set up and analyzed by χ2test using SPSS13.0statistical software. Theresult would be statistically significant when the value of p was less than0.05.ResultIn246cases undergoing MRCP, eight patients were excluded because of difficulty indetermining the branching patterns of IHD due to incomplete opacification. There were238cases whose IHDs were displayed clearly. The frequencies of each type of intrahepaticduct variations were as follows: typical pattern in42.9%(n=102), triple confluence in30.7%(n=73), anomalous drainage of the RPSD into the LHD in7.1%(n=17),anomalous drainage of the RPSD into the CHD in7.1%(n=17), anomalous drainage of the RPSD into CBD in0.4%(n=1), presence of an accessory duct leading to the RHD in6.3%(n=15), presence of an accessory duct leading to the CHD in2.1%(n=5), presenceof an accessory duct leading to the LHD in2.5%(n=6), segmental ducts from segments IIand III separately leading to the RHD or CHD in2.1%(n=5). In the136cases with thevariations of IHDs,26cases were discovered with hepatolithiasis,110cases withouthepatolithiasis;10cases were discovered with cholangiocarcinoma,126cases withoutcholangiocarcinoma. In the102cases with typical anatomy of IHDs,9cases werediscovered with hepatolithiasis,93cases without hepatolithiasis;6cases were discoveredwith cholangiocarcinoma,96cases without cholangiocarcinoma. The incidences ofhepatolithiasis between the cases with the variations and typical anatomy of IHDs werecompared by χ2test (χ2=4.924，P=0.026). There was significant difference, so the caseswith variations got higher incidence of hepatolithiasis than those with normal anatomy.The incidences of cholangiocarcinoma between the cases with the variations and typicalanatomy of IHDs were compared by χ2test (χ2=0.201，P=0.654). The statistical resultindicated that the cases with the variations and typical anatomy of IHDs had insignificantdifference in the incidence of cholangiocarcinoma.In246cases undergoing MRCP, there were188cases whose cystic ducts weredisplayed clearly and107cases with the cystic duct variations, so the incidence ofvariations is56.9%. The cases of each type of cystic duct variations were as follows: highdrain into the bifurcation of LHD and RHD in11cases, low drain into CHD in6cases,pronation or supination bypassing CHD into the left edge in22cases, parallelism withCHD in51cases, short cystic duct in4cases, negative angle in24cases, cystiform dilationin4cases. In the107cases with the variations of cystic duct,76cases were discoveredwith gallstone and cholecystitis,31cases without gallstone and cholecystitis;11caseswere discovered with cholangiocarcinoma,96cases without cholangiocarcinoma. In the81cases with typical anatomy of cystic duct,46cases were discovered with gallstone andcholecystitis,35cases without gallstone and cholecystitis;5cases were discovered withcholangiocarcinoma,76cases without cholangiocarcinoma. The incidences of gallstoneand cholecystitis between the cases with the variations and typical anatomy of cystic ductwere compared by χ2test (χ2=4.102，P=0.043). There was significant difference, so thecases with variations got higher incidence of gallstone and cholecystitis than those withnormal anatomy. In this paper, we made statistics of the cases of each type of cystic ductvariations with gallstone and cholecystitis. The result was as follows: high drain into thebifurcation of LHD and RHD in8cases, low drain into CHD in3cases, pronation or supination bypassing CHD into the left edge in16cases, parallelism with CHD in38cases,short cystic duct in2cases, negative angle in15cases, cystiform dilation in2cases,parallelism with CHD into the left edge in5cases, parallelism with CHD and low draininto CHD in1cases. Thus, the cases with the cystic duct parallel with CHD were mostlikely to suffer from gallstone and cholecystiasis. The incidences of cholangiocarcinomabetween the cases with the variations and typical anatomy of cystic duct were compared byχ2test (χ2=0.999，P=0.318).The statistical result indicated that the cases with thevariations and typical anatomy of cystic duct had insignificant difference in the incidenceof cholangiocarcinoma.The incidences of the variations of IHDs and cystic duct were compared by χ2test (χ2=0.002, P=0.962). The statistical result indicated that there was insignificant differencein the incidences of the variations of IHDs and cystic duct.ConclusionThe incidences of IHDs and cystic duct variations are high and have insignificantdifference. In this paper, the branching pattern of IHDs was atypical in57.1%of cases, andthe most common variation was triple confluence of the RASD, RPSD and LHD (30.7%).The branching pattern of cystic duct was atypical in56.9%of cases, and the most commonvariation was the cystic duct parallel with CHD (27.1%).Compared with the international common typing standard, anomalous drainage ofRPSD into the cystic duct was not seen in this paper. We supplemented another two types,that is, anomalous drainage of the RPSD into CBD and presence of accessory duct leadingto the LHD.The ones with variations of IHDs and cystic duct are more likely to suffer fromhepatolithiasis and gallstone than those with typical anatomy of IHDs and cystic duct. Theone with the cystic duct parallel with CHD is most likely to suffer from gallstone andcholecystiasis.The accurate rate of diagnosing biliary obstructive diseases by MRCP is very high.Thus, MRCP can provide important reference value for differentiating pancreaticobiliaryduct system diseases.The variations of IHDs and cystic duct could be displayed clearly by MRCP. As aroutine examination before surgery or interventional therapy, MRCP is of greatsignificance for avoiding iatrogenic duct injuries and reducing the incidence ofpostoperative complications.