the choledochal cyst can be defined as a congenital anomaly of the biliary system , characterized by cystic dilatation of the intrahepatic duct and the extrahepatic biliary tree individually , or cystic dilatation of both these parts simultaneously .
it has been reported that the incidence of choledochal cyst in western countries ranges from 1:100,000 to 1:150,000 live births , and its incidence in japan has been frequently reported to be 1:1,000 live births .
however , the precise incidence of choledochal cyst in korea has not been reported so far .
it has been known that choledochal cysts are caused by two main factors , namely , weakening of the bile duct walls and an obstruction distal to it .
in addition to the causes of this disease , a close relationship between the choledochal cyst and pancreaticobiliary malunion ( pbmu ) has also been revealed .
also , the probability of occurrence of pbmu related to the position of the opening of the papilla of vater and the probability of the occurrence of choledochal cyst related to such a situation has been considered to be one of the causes , and recently a series of reports have been made available . in this connection
, we report our experience of choledochal cyst with pbmu and the papilla of vater positioned in the third portion of the duodenum , in a 30-month - old boy .
a 30-month - old boy , who was suffering from vomiting and abdominal pain since the past 20 days , underwent abdominal computed tomography ( ct ) scans at another hospital and was then transferred to our hospital under the impression of choledochal cyst .
there was no particular past medical history or family history , except for the history of hospitalization for treatment of pneumonia one month prior to being admitted to our hospital .
laboratory data including complete blood count and urinalysis were within the normal limits , but blood biochemistry revealed the following : aspartate aminotransferase 121 iu / l , alanine aminotransferase 155
iu / l , gamma - glutamyl transpeptidase 168 iu / l , amylase 292 iu / l and lipase 129 u / l , showing elevated levels and t - bilirubin / d - bilirubin were 0.59 mg / dl and 0.16 mg / dl respectively , showing normal levels .
abdominal ct demonstrated dilatation of the extrahepatic bile duct and central dilatation of the intrahepatic bile duct ( fig .
1 ) . also magnetic resonance cholangiopancreatography demonstrated findings similar to abdominal ct but it could not identify the pbmu ( fig .
, the hepatic uptake appeared to be within the normal range , however , the accumulation of isotope at the common bile duct ( cbd ) and delayed excretion into the duodenum were confirmed based on the findings . under the diagnosis of choledochal cyst
the operation was carried out , and the p - b type of pbmu , in which the pancreatic duct joins the cbd , and the papilla of vater is positioned in the third portion of the duodenum were identified through the operative cholangiography ( fig .
, the diagnosis of a type i choledochal cyst was confirmed , and hence excision of the choledochal cyst and , roux - en - y hepaticojejunostomy were carried out .
the patient was discharged on postoperative day 11 without any problems and in good general health condition .
choledochal cysts are congenital anomalies of the biliary system and consist of cystic dilatation of the extrahepatic biliary tree , intrahapatic biliary ducts or both . based on the clinical and anatomic findings of choledochal cysts , todani and
others argued that choledochal cysts can be divided into 5 major types and these types can be further divided into 3 subcategories . despite their classification into many types , the surgical method of treatment for each type is not far different from the conventional method of treatment for choledochal cysts .
many studies on the pathogenesis of various types of choledochal cysts and their relationship with the adjacent structures are in full swing and are being reported .
and in cholangiographic techniques , there has been a series of reports which suggest that there is a high possibility of a relationship between the choledochal cyst and pbmu .
a hepatic diverticulum appears in the ventral wall of the primitive midgut early in the 4th week of intrauterine life in the development of the human embryo .
the extrahepatic bile duct system and the ventral pancreas arise from the hepatic diverticulum during the 4th to 6th week of intrauterine life .
the main duct of the ventral pancreatic bud develops near the entry of the cbd into the duodenum . as the duodenum rotates to the right and
become c - shaped , the ventral pancreatic bud is carried dorsally with the bile duct .
the superior ventral branch of the ventral pancreas joins the distal portion of the dorsal pancreatic duct to form the main pancreatic duct , which merges with the cbd , inserting into the duodenum via the papilla of vater .
the papilla of vater is generally situated halfway down the medial wall towards the posterior aspect of the descending or second part of the duodenum .
there have been rare cases in which the papilla of vater was found in a position other than its normal position and such cases have been reported sporadically .
however , such cases are interesting in the anatomical context . especially , very few cases have been reported in which the papilla of vater opens in the third portion of the duodenum [ 8 - 10 ] . in a series of recent studies , it has been reported that the frequency of choledochal cyst in patients was higher when the papilla of vater was positioned distal to its normal position . in this context from the anatomical viewpoint ,
the ectopic distal location of the papilla of vater represents the ectopic distal budding of the hepatic diverticulum during early embryonic life , it is straightforward to postulate that the longer distance between the ventral and dorsal pancreatic buds may result in a delay in communication of the ventral duct with the dorsal duct or failure of communication . and also the formation of pbmu at the early embryonic stage is caused by canalization of ventral pancreatic duct and the anomalous union of pancreaticobiliary duct , which originate from the dislocation of the ventral pancreas , and it is also caused by the stretching of primitive common channel and cbd in accordance with the lengthening , which will result in a long cbd and a long common channel .
therefore , if growth of the epithelium in the cbd , the common channel and the pancreatic duct fails keep up with this anomalous elongation during fusion , the ducts may become attenuated , resulting in stenosis and weakness of the duct walls , and subsequent dilatation of the ducts , a phenomenon that has been observed clinically .
this suggests that the lengths of the common channel and the cbd in patients with choledochal cyst correlate strongly with the location of the papilla of vater , i.e. , the more distal the papilla of vater is , the longer the common channel and the cbd . in conclusion ,
we have reported a case of a 30-month - old child with choledochal cyst , in whom the form of pbmu occurred simultaneously and the papilla of vater was positioned in the third portion of the duodenum .
there is no difference in the conventional surgical method of treatment in such cases despite the variation in the opening position of the papilla of vater .
but the likely relationship between the opening position of the papilla of vater and choledochal cyst should be considered when a variation in the opening position of the papilla of vater is detected before surgery .
 in cholangiographic techniques , the close relationship between choledochal cyst and anomalous union of pancreaticobiliary duct has attracted medical attention . 
 there have been rare cases in which the papilla of vater was found in a position other than its normal position , and such cases have been reported sporadically . 
 however , such cases are interesting in the anatomical context . in this review 
 , we present our experience of choledochal cyst in a 30-month - old boy in whom the papilla of vater was positioned in the third portion of the duodenum . 
INTRODUCTION
CASE REPORT
DISCUSSION