Objective To explore the pathogenesis of congenital choledochal cysts (CCC) by detecting enteric neural abnormalities in CCC.Methods From 2007 to 2009,36 children with CCC underwent choledochal cyst excision and hepaticojejunostomy.Their proximal and distal cystic wall specimens were incised respectively and selected as the experimental group.At the same time,the extrahepatic bile ducts of 15 fetus who were late terminated because of unplanned pregnancy were selected as the control group.The expression of NGF and its receptors (p75NGFR and TrkA),NSE,S-100,Cajal interstitial cells and SY between two groups were compared and the correlation between each index and cysts' diameters was analyzed in order to understood the relationship between the pathogenesis of CCC and neural abnormalities.Results The expression levels of all indicators in the distal cysts were weaker than those in the proximal ones (F=2.694,2.667,1.833,1.750,1.667,2.139,0.861,P<0.05).There was significant difference in the expression of indicators except SY between distal cysts and fetal bile duets ( F =2.734,3.552,3.448,2.996,3.337,3.155,P <0.05) ; There was no significant difference between the proximal cysts and fetal bile ducts except TrkA and S-100 ( F =0.040,0.885,1.246,1.016,0.242,P >0.05 ).The expression of NGF,NSE,S-100 and c-kit in distal cysts had a negative correlation with the diameter of cysts ( rs =- 0.739,- 0.787,- 0.577,- 0.798,P < 0.05 ) ; There was a positive correction between the expression of NGF with p75NGGR,NSE,S-100 and c-kit in distal cysts ( P < 0.05 ),between the expression of c-kit with p75NGFR,NSE,S-100,as well as between the expression of NSE with S-100.Conclusion The restriction of enteric nerve distribution and maturation in distal biliary tract,coupled with nerve-muscle transmission badness due to embryonic dysplasia may cause CCC.The size of cyst is closely related to the upgrowth,distribution and nerve conduction of enteric nerve cells in distal biliary tract. Key words: Congenital choledochal cysts; Enteric nerve; Dysplasia