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Choledochal cyst
A choledochal cyst is a congenital dilatation of the bile ducts usually caused by an abnormal junction of the pancreatic duct with the bile duct; treatment is complete excision of the cyst with a Roux-en-Y hepaticojejunostomy — not drainage — because of the risk of malignancy.
Why it matters in the exam
The exam asks about the Todani classification, the test of choice (MRCP), the reason for complete excision and the limits of resection. Type I (dilatation of the common bile duct, cystic or fusiform) is the most common; type IV includes cysts both inside and outside the liver; type III is a choledochocele within the duodenal wall; type V is Caroli disease — dilatation of the intrahepatic ducts only.
The accepted mechanism is an abnormal pancreaticobiliary junction with a "long common channel", allowing pancreatic enzymes to flow into the bile ducts, with inflammation and dilatation. In infants the presentation is cholestatic jaundice, sometimes with an abdominal mass, and the cyst is sometimes seen on fetal ultrasound. In older children — abdominal pain, recurrent pancreatitis and cholangitis; the triad of "pain, jaundice and mass" occurs only in a minority. Ultrasound is the screening test, and MRCP defines the anatomy and the pancreaticobiliary junction.
In surgery for type I the whole cyst is excised: the proximal limit is the common hepatic duct below the bifurcation, and the distal limit is the junction with the pancreatic duct, taking care not to injure it. Anastomosis between the cyst and the bowel (internal drainage) has been abandoned because it leaves mucosa that can transform into cholangiocarcinoma, and the risk of malignancy rises with age. After surgery follow for anastomotic stricture, cholangitis and intrahepatic stones. Type III can usually be treated endoscopically, and in diffuse Caroli disease liver transplantation is considered.
Key points
- Cause: an abnormal pancreaticobiliary junction with a long common channel.
- Type I is the common type.
- MRCP is the test of choice.
- Complete excision and Roux-en-Y hepaticojejunostomy — not drainage.
- The risk of cholangiocarcinoma rises with age.
Summary table
| Todani type | Description | Treatment |
|---|---|---|
| I | Dilatation of the common bile duct (the common type) | Complete excision and Roux-en-Y hepaticojejunostomy |
| II | Diverticulum of the bile duct | Excision of the diverticulum |
| III | Choledochocele in the duodenal wall | Endoscopic treatment (sphincterotomy) or local excision |
| IV | Multiple cysts, inside and outside the liver | Excision of the extrahepatic part and anastomosis; sometimes liver resection |
| V (Caroli) | Intrahepatic dilatation only | Lobectomy for localised disease; transplant for diffuse disease |
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Sources
- Holcomb and Ashcraft's Pediatric Surgery, 7th edition (2019) — Choledochal Cyst and Gallbladder Disease
- Blumgart's Surgery of the Liver, Biliary Tract and Pancreas, 7th edition (2023) — Bile duct cysts in adults and children
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.