Choledochal Cysts: Presentation, Clinical Differentiation, and Management

摘要

Abbreviations and Acronyms APBDU: anomalous pancreaticobiliary duct union; BA: biliary atresia; CBA: cystic biliary atresia; CBD: common bile duct; CC: choledochal cyst; CHD: common hepatic duct; MRCP: magnetic resonance cholangiopancreatography; OLT: orthotopic liver transplant; RYHJ: Roux en Y hepaticojejunostomy. Choledochal cysts (CC) are a rare congenital cystic dilation of the biliary tract, first described by Vater and Ezler in 1723.1 They present primarily in female infants and young children and are more prevalent in East Asian populations. Although benign, CC can be associated with serious complications including malignant transformation, cholangitis, pancreatitis, and cholelithiasis.2 We herein provide a state-of-the-art, evidence-based review of CC with particular emphasis on clinical differentiation and approach to management. A search of the available electronic databases, including MEDLINE/Pubmed, using the term choledochal cyst as well as under the MeSH database subheading choledochal cyst, was performed. Criteria for inclusion included English articles (Fig. 1).Figure 1.: A Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) diagram defining the method of inclusion and exclusion for studies used.Incidence and epidemiology Approximately 80% of CC are diagnosed in infants and young children within the first decade of life.3,4 The incidence of CC ranges from 1 in 100,000 to 1 in 150,000 individuals in Western countries5 to 1 in 13,000 individuals in Japan.6 Choledochal cysts are 4 times more common in females.2,7,8 Although the exact etiology is unknown, anomalous pancreaticobiliary duct union (APBDU) is seen in 30% to 70% of all CC where the common bile duct (CBD) and pancreatic duct junction occurs outside the duodenum, allowing reflux of pancreatic fluid into the biliary tree.9-13 The exposure of biliary epithelium to digestive and caustic pancreatic enzymes may contribute to CC formation. In 1969, Babbitt14 initially described APBDU, and it is believed to be secondary to arrest in migration of the choledochopancreatic junction into the duodenal wall, leading to a long common channel (Fig. 2).15 A long common channel is defined as insertion of the CBD farther than 15 mm from the ampulla of Vater.16 It occurs in less than 2% of the population,16 although it is more commonly seen in pediatric CC patients. Eighty percent to 96% of pediatric CC are associated with APBDU.2,13,17 In one series of 2,885 patients undergoing ERCP, nearly 90% of patients diagnosed with an APBDU had a CC.16 Animal studies have given credence to this theory since iatrogenic APBDU in murine models demonstrated cystic dilatation of the CBD.18,19 Amylase levels in the fluid contained in the gallbladder and CC are typically elevated in patients with APBDU.13 Other pathophysiologic mechanistic hypotheses for CC include a weak bile duct wall, sustained increased intrabiliary pressure, inadequate autonomic innervations, sphincter of Oddi dysfunction, and distal obstruction of the CBD.5,20,21Figure 2.: Common channel in a 4-year-old girl. (A) ERCP image revealing dilated intra- and extrahepatic ducts. Notice that the pancreatic duct (PD) drains (arrow) into the mid common duct (CD). (B) MRCP in the coronal oblique plane showing better delineation of the insertion point (arrow) of the pancreatic duct. The right (Rt) and left (Lt) intrahepatic ducts are also well visualized. Notice debris in the distal common duct.Classification Alonso-Lej and colleagues20 proposed the first CC classification in 1959. Komi and associates11 later proposed a new CC classification according to the type of APBDU based on 2 unique features: a long common channel and the angle of the junction between the pancreatic duct and distal CBD as they converge on the sphincter of Oddi.5 However, the most widely accepted classification was reported by Todani and colleagues22 in 1977, derived from the original Alonso-Lej classification and based on the site