Choledochal cyst

Choledochal cysts represent congenital cystic dilatations of the biliary tree. Diagnosis relies on the exclusion of other conditions (e.g. tumour, gallstone, inflammation) as a cause of biliary duct dilatation.


Choledochal cysts are rare, with an incidence of 1:100,000-150,000. Although they may be discovered at any age, 60% are diagnosed before the age of 10 years 1.  There is a strong female predilection with a M:F ratio of 1:4. There is a greater prevalence in East Asia.

Clinical presentation

Classically presentation includes the triad of 1:

  • abdominal pain
  • jaundice
  • abdominal mass

This triad is however only present in ~40% (range 19-60%) of cases, with palpable mass being the least common manifestation.


Their aetiology is uncertain but a close association with anomalous formation of the pancreaticobiliary ductal junction is reported in some subtypes 1. Due to this anomaly, there is a large common channel draining pancreatic and bile duct. Thus the pancreatic juices cause cholangitis and bile duct wall destruction, which together with distal stenosis due to scarring, result in formation of choledochal cyst.


A number of associations are recognised, including 1


Commonly accepted classification currently is one devised by Todani et al. There are five main types, with several subtypes some of which can be pathologically unrelated:

  • type I: most common, accounting for 80-90% 1 (this type can present in utero)
    • Ia: dilatation of extrahepatic bile duct (entire)
    • Ib: dilatation of extrahepatic bile duct (focal segment)
    • Ic: dilatation of the common bile duct portion of extrahepatic bile duct
  • type II: true diverticulum from extrahepatic bile duct
  • type III: dilatation of extrahepatic bile duct within duodenal wall (choledochocoele)
  • type IV: next most common
    • IVa: cysts involving both intra and extrahepatic ducts
    • IVb: multiple dilatations/cysts of extra hepatic ducts only
  • type V: multiple dilatations/cysts of intra hepatic ducts only (Caroli disease)

The Todani classification scheme has been called into question in surgical literature, with claims that it may unfairly link multiple distinct processes into a spuriously coherent grading scheme 7,8.

The Komi classification classifies choledochal cyst into 3 types based on the anomalous union of the pancreatic-bile duct (AUPBD) 2.

Radiographic features

Imaging of the biliary tree can be achieved with ultrasound, CT, direct contrast studies (ERCP, PTC) or MRI.


Key to the diagnosis is a dilated cystic lesion which communicates with the bile duct and is separate from the gall bladder. Careful search for other causes needs to also be undertaken (see differential below), remaining cognisant that both stone formation and malignancy are associated with choledochal cysts.


Findings are similar to US, with a greater ability to demonstrate intrahepatic disease. It is important to remember that with CT IVC the contrast mixing in the cyst may be inhomogeneous. It does however have the advantage that it conclusively demonstrates communication with the biliary tree 1.

Treatment and prognosis

The only feasible treatment is surgical excision, with reconstruction. A number of possible approaches exist, depending on cyst location and other factors. Typically a Roux-en-Y hepaticojejunostomy is performed 1.


The two most frequent complications of choledochal cysts are stone formation and malignancy. Complications include:

  • stone formation: most common
  • malignancy
  • cyst may rupture leading to bile peritonitis
    • most frequently seen in neonates 1
  • pancreatitis

Differential diagnosis

General imaging differential considerations include:

See also

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