The Relationship Between Anatomic Variations Of The Cystic Duct And Gallstone,Intrahepatic Stone:an MRI Study

Objectives: To investigate the role played by the cystic duct with anatomical variations in the formation of gallstone and intrahepatic stone by MRI conventional sequences combined with Magnetic Resonance Cholangiopancreatography(MRCP).Materials and methods:The MRI and clinical data of patients who underwent MRI and MRCP at the affiliated hospital of North Sichuan Medical college from January 2013 to June 2014 was collected retrospectively. According to the level,radial orientation,and the course of the cystic duct draining into the biliary system on the MRI sequences,the cystic ducts were classified into following types.1)Middle level cystic duct,including the cystic duct with the insertion to the right(normal cystic duct),front,back,and left side of upper 1/2 part extrahepatic bile duct(EBD),and the parallel cystic duct draining into the upper half of EBD.2)Low cystic duct,including cystic duct mere insertion to the lower 1/2 part of EBD and the low cystic duct with a parallel course.3)the cystic duct insertion to hepatic biliary duct( left,right hepatic bile duct or either their branches and confluence,or accessory hepatic duct). 4)short cystic duct( the length of which was shorter than 5mm).The patients were diagnosed gallstone or intrahepatic stone if they meet one of following three diagnostic criterias:1)found gallstone or intrahepatic stone by operation,2)both MRI and ultrasonography or computed tomography found gallstone or intrahepatic stone,3)without neither the ultrasonography nor CT examination record,but had typical imaging features of gallbladder stone or intrahepatic stone on the MRI sequences.The prevalence rate of gallbladder stone or intrahepatic stone between the normal cystic duct and each variation type was compared by spss13.0 statistics software.Result:1.Of the 737 patients included in the study,324(43.96%)patients showed a normal cystic duct.The remaining 413(56.04%) patients had anatomic variations.Among these variations,middle level cystic duct with front,back and left side in 36(4.88%),186(25.24%),36(4.88%) patients respectively had been viewed,a parallel cystic duct with middle level was seen in 15 patients(2.04%), merely low cystic duct in 48(6.51%) cases was observed, low cystic duct with a parallel course in 49(6.65%) patients was detected, the cystic duct draining into hepatic bile duct in 34(4.61%) cases and short cystic duct in 9( 1.22%) patients were viewed.2.Among these variations mentioned above,only the patients with merely low cystic duct and low cystic duct with a parallel course showed significant high prevalence rate of gallstone(43.75%、46.94%)when compared with normal cystic duct patients(25.31%,P<0.05).3.The prevalence rate of intrahepatic stone between each types of abnormal cystic duct and normal cystic duct was not statistically significant(P>0.05).Conclusion:There is a high incidence of the anatomic variation of the cystic duct.They may not relate to intrahepatic stone, but low cystic duct and low cystic duct with a parallel course may promote gallstone formation.