Mixed Choledochal Cyst (type I and II) Associated With a Malformation of the Pancreatobiliary Junction. A Case Report and Review of the Literature.

Choledochal cysts are a rare disease, with an incidence in western countries of 1 in 100 000–150 000 births. The rate is considerably higher in Asian populations, where the reported incidence is 1 in 1000 births. The exact etiology is still unknown, although they predominantly affect females with a ratio of 4:1. According to the Todani classification, the distribution of the different types of choledochal cysts is: type I 50%–80%; type II 2%; type III 1.4%–4.5%; type IV 15%–35%; type V 20%. Mixed type I and II choledochal cysts are extremely rare and represent less than 1.1% of cases. A review of the literature has found only 6 reported cases. Around 80% present with symptoms before the age of 10. The described symptomatic triad of abdominal pain, jaundice and a palpable abdominal mass occurs in less than 20%. The complications of choledochal cysts include bile stasis, the formation of calculi, recurring infections and inflammation. The initial study of these patients involves ultrasound, which is able to establish a diagnosis in most cases. The pancreato-biliary malformations entail a common canal between the junction of the pancreatic duct and the bile duct, which are outside the duodenal wall. These malformations are a risk factor for neoplasms of the biliary tract. Pancreatic juices and bile combine constantly, producing toxic substances. Due to this, the mucus of the bile tract is repeatedly damaged and repaired on many occasions, which causes an acceleration of proliferative activity and multiple gene mutations. In turn, this causes histological changes, such as hyperplastic epithelium, metaplastic epithelium, and dysplastic epithelium, which lead to carcinogenesis of the bile duct. The frequency of anomalies at the pancreato-biliary junction ranges between 0.08% and 3.2% of the population. Kimura defined 2 types of anomalies of the pancreato-biliary junction. In type 1, the pancreatic duct empties into the common bile duct at an acute angle and the distal bile duct does not have stenosis. In type 2 (95%), it is the common bile duct that empties into the pancreatic duct and the distal bile duct usually presents stenosis; therefore, there is greater and earlier dilatation of the bile duct. In this article, we report the case of a mixed type I and II choledochal cyst associated with a Kimura type 2 malformation of the pancreato-biliary junction. Case Report