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KEY POINTS
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Key Points

  • Choledochal cyst refers to dilation of the common bile duct, with type I being the most common and the only prenatally diagnosed form.

  • Prenatal diagnosis is based on the visualization of a single simple cystic structure near the gallbladder.

  • Differential diagnosis includes hepatic, adrenal or renal cysts, duodenal duplication, and gallbladder duplication.

  • There is no need to alter the management of pregnancy, nor the timing or mode of delivery, following the prenatal diagnosis of choledochal cyst.

  • During the newborn period, detailed imaging of the biliary system is required to exclude biliary atresia, including radionuclide imaging.

  • Definitive treatment requires surgical excision of the cyst, and long-term outcome is excellent.

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CONDITION
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Choledochal cysts are rare congenital cystic dilations of the biliary tree and are classified by the portion of the biliary tree affected. The most common form consists of fusiform dilation of the common bile duct (Figure 67-1). Type I choledochal cyst accounts for 85% to 90% of all cases. All cases of choledochal cyst that have been diagnosed prenatally, to date, have been of the type I variety (Bancroft et al., 1994). The less common forms of choledochal cyst include diverticulum of the common bile duct (type II), which are intraduodenal or intrapancreatic; choledochocele (type III); multiple extrahepatic cysts with or without intrahepatic cysts (type IV); and Caroli’s disease, which consists of single or multiple intrahepatic cysts associated with hepatic fibrosis and a normal extrahepatic biliary tree (type V) (Caroli et al., 1958).

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Figure 67-1

Classification scheme of choledochal cysts. Type I is the most common form, with cystic dilation of the extrahepatic bile ducts but normal intrahepatic ducts. Type II is a cystic diverticulum of the common bile duct. Type III is a diverticulum of the distal common bile duct or choledochocele. Both types II and III are rare. Type IV is the second most common form, with cystic dilation of both the extrahepatic and intrahepatic ducts. Type V, or Caroli’s disease, has cystic dilation of the intrahepatic ducts but relatively normal extrahepatic ducts. In forme fruste (FF), the extrahepatic ducts are diseased but have only mild or negligible cystic dilation and the intrahepatic ducts have cystic dilation.

Graphic Jump Location
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The wall of a choledochal cyst is usually thickened with dense connective tissue interlaced with strands of smooth-muscle fibers associated with some inflammatory reaction (O’Neill et al., 1987). Normal biliary mucosal lining is absent, although sparse islands of columnar epithelium and microscopic bile ducts within the wall may be seen. In older patients, stones may be seen within the choledochal cyst or within intrahepatic ducts (Landing, 1974; Bhagvat and Chaudhrey, 1989). Most newborns with choledochal cysts have complete biliary obstruction at the level of the duodenum, which has been likened to a form of ...

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