Choledochal Cyst

Published on 19/07/2015 by admin

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Last modified 22/04/2025

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 Diagnosis requires excluding other causes of biliary dilatation, including tumor, stone, or stricture

image Commonly associated with cholelithiasis, cystolithiasis, choledocholithiasis, and hepatolithiasis
• Classified into 5 types based on Todani classification

image Type I: Fusiform/cystic dilation of extrahepatic duct
image Type II: True diverticulum of supraduodenal ED
image Type III: Dilation limited to intraduodenal segment of ED (a.k.a. choledochocele), with dilated segment of duct located within duodenal wall
image Type IV: Presence of multiple biliary cysts, at least 1 of which must involve extrahepatic bile duct
image Type V: Single or multiple intrahepatic biliary cysts, with multiple intrahepatic cysts known as Caroli disease

PATHOLOGY

• Etiology may be related to anomalous pancreaticobiliary junction or congenital ductal plate malformation

CLINICAL ISSUES

• Most common in female patients, often of Asian descent
• Usually diagnosed in infancy and childhood
• Classic triad of symptoms: Recurrent RUQ pain, jaundice, and palpable mass
• Complications: Stones, cholangitis, pancreatitis, or malignant degeneration (cholangiocarcinoma or gallbladder cancer)
• Treatment varies depending on type of choledochal cyst, but type I and IV cysts typically undergo surgical excision and reconstruction by Roux-en-Y hepaticojejunostomy
image
(Left) This graphic shows the Todani classification of choledochal cysts. Note that type I is fusiform dilation of the extrahepatic duct (ED). Type II is a true diverticulum of the supraduodenal ED. Type III is an isolated choledochocele. Type IV is fusiform dilation of the extrahepatic duct and intrahepatic ducts, and type V is synonymous with Caroli disease.

image
(Right) Coronal CECT reformation of a type I choledochal cyst shows fusiform dilatation of the extrahepatic duct image. Type I lesions are the most common type of choledochal cyst.
image
(Left) Curved multiplanar CECT reformation along the length of the extrahepatic duct shows a small choledochocele image protruding into the duodenal lumen and mild dilation of the common bile duct image. This is either a type III or IVb choledochal cyst, depending on whether the ED is considered to be involved.

image
(Right) Coronal MRCP in the same patient nicely shows the choledochocele image protruding into the duodenal lumen and the mildly dilated extrahepatic duct image, along with numerous stones in the gallbladder image.

TERMINOLOGY

Synonyms

• Biliary cyst

Definitions

• Congenital segmental cystic dilatation of intrahepatic or extrahepatic bile ducts, most commonly affecting main portion of extrahepatic duct (ED)

IMAGING

General Features

• Best diagnostic clue

image MR cholangiopancreatography (MRCP): Fusiform dilatation of bile duct
• Location

image Most commonly affects extrahepatic CD (80-90%)
• Size

image Varies from 2-15 cm
• Morphology
• Rare disorder usually diagnosed in infancy and childhood, but is most common congenital lesion of large bile ducts

image Often coexists with other cystic and fibrotic disorders of liver (e.g., Caroli disease, biliary hamartomas, congenital hepatic fibrosis)
• Segmental cystic dilatation of bile ducts with dilated segments maintaining communication with biliary tree

image Diagnosis requires excluding other causes of biliary dilatation, including tumor, stone, or stricture
image Commonly associated with cholelithiasis, cystolithiasis (stones within choledochal cyst), choledocholithiasis, and hepatolithiasis
image Most commonly classified into 5 different types based on Todani classification 

– 2003 modification of Todani classification incorporates presence of abnormal pancreaticobiliary junction (APBJ)
– Type I: Solitary fusiform or cystic dilation of extrahepatic bile duct (ED)

image Type Ia: Cystic dilation of entire ED; associated with abnormal pancreaticobiliary junction (APBJ)
image Type Ib: Focal dilation of ED (often distal); no association with APBJ
image Type Ic: Fusiform dilation of entire ED; associated with APBJ
image Most common type, constituting 50-85% of choledochal cysts
image Much more common in females than males (3:1) and may present with pain, jaundice, or gallstone formation (due to bile stasis)
image Differentiate from distal obstruction of ED (e.g., stone or tumor) or mild normal dilatation of ED after cholecystectomy
image Mild dilation of right and left ducts may blur distinction with type IVa
– Type II: True diverticulum of supraduodenal ED 

image Very rare, accounting for only 2% of cases
image Only a few reports of type II choledochal cysts in literature
– Type III: Dilation limited to intraduodenal segment of ED (a.k.a. choledochocele), with dilated segment of ED located within duodenal wall

image Type IIIa: Cystic dilation of intraduodenal ED
image Type IIIb: Diverticulum of intraduodenal ED
image Constitutes 1-5% of cases
image Cyst may be lined by either duodenal or biliary epithelium
image Large choledochoceles may obstruct duodenum, present with jaundice, or cause pancreatitis
– Type IV: Presence of multiple biliary cysts, at least 1 of which must involve extrahepatic bile duct

image IVa: Involvement of both intrahepatic and extrahepatic ducts; 2nd most common overall, comprising 40% of cases diagnosed in adults
image IVb: Multiple extrahepatic cysts with no intrahepatic cysts
image Constitutes 15-35% of cases
– Type V: Single or multiple intrahepatic biliary cysts, with presence of multiple intrahepatic cysts known as Caroli disease

image No involvement of extrahepatic duct

Radiographic Findings

• Radiography

image Upper gastrointestinal series

– Anterior displacement of 2nd part of duodenum and antrum
– Inferior displacement of duodenum
– Widening of duodenal sweep
• ERCP: Considered gold standard modality for diagnosis of choledochal cysts

image Accurate means of evaluating pancreaticobiliary junction
image May have trouble delineating some portions of biliary tree in cases with coexistent strictures

CT Findings

• Nonenhancing cystic structure (types I, II, or IV) in porta hepatis contiguous with biliary tree

image Multiplanar images critical for establishing contiguity of cyst with biliary tree
• Cystic intramural mass within wall of proximal duodenum communicating with CBD (type III)
• Multiple intrahepatic cysts in close contiguity with intrahepatic bile ducts (type IV)

MR Findings

• Best noninvasive modality for assessing biliary tree, choledochal cysts, and anomalous pancreaticobiliary junction
• MRCP images nicely demonstrate cystic dilatation of biliary tree and relationship (and communication) of cysts with adjacent bile ducts
• Choledochal cysts should mirror signal intensity of normal bile ducts (hypointense on T1WI, hyperintense on T2WI, and no perceptible wall enhancement on T1WI C+)
• Presence of abnormal wall hyperenhancement or thickening should raise concern for superinfection or malignancy (particularly with nodular or irregular wall thickening)

Ultrasonographic Findings

• Grayscale ultrasound

image Anechoic lesion in porta hepatis (types I, II, or IV) with posterior acoustic enhancement 

– Can be confused with gallbladder or mesenteric cyst, unless communication with extrahepatic bile duct is established
– Gallstones may be present within cyst (with posterior acoustic shadowing)
image Multiple intrahepatic cysts (type IV or V) with acoustic enhancement

– Communication with biliary tree may be difficult to establish for intrahepatic cysts using ultrasound

Nuclear Medicine Findings

• Hepatobiliary (HIDA) scan

image Photopenic area in liver or porta hepatis that shows late filling and prolonged retention (often > 24 hours) of radiotracer
image Presence of radiotracer within cyst definitely identifies structure as communicating with biliary tree

– May be confused with other causes of obstructed bile ducts

Imaging Recommendations

• Best imaging tool

image MRCP; ERCP if endoscopic intervention is being considered

DIFFERENTIAL DIAGNOSIS

Malignant Common Bile Duct (CBD) Obstruction

• Often secondary to pancreatic adenocarcinoma, ampullary carcinoma, or distal CBD cholangiocarcinoma
• Dilatation of bile ducts proximal to obstruction, with pancreatic duct also dilated with most pancreatic and ampullary tumors
• Abrupt, irregular narrowing of distal CBD differentiates tumor from choledochal cyst
• Extrahepatic: Short stricture or small polypoid mass
• CECT: Hypovascular, delayed enhancing mass surrounding CD
• ERCP: Abrupt irregular obstruction of antegrade and retrograde flow of contrast

Primary Sclerosing Cholangitis

• Idiopathic inflammatory condition leading to progressive fibrosis and strictures of intra- and extrahepatic bile ducts
• Multifocal “beaded” strictures with alternating sites of stricture, dilatation, and normal-sized ducts
• Bile duct wall may be thickened and hyperenhancing in setting of acute inflammation
• “Beading” and irregularity of ducts (with only minimal ductal dilatation) distinct from cystic or fusiform dilatation of choledochal cysts

Recurrent Pyogenic Cholangitis

• Formation of pigment stones throughout biliary tree (both intrahepatic and extrahepatic) with multiple biliary strictures, recurrent bouts of cholangitis, and dilatation of both intrahepatic and extrahepatic bile ducts
• Disproportionate dilatation of extrahepatic and central intrahepatic ducts, but may cause localized intrahepatic biliary dilatation (often in left lobe)

image Cylindrical morphology of dilated ducts with intervening strictures (unlike cystic dilatation of choledochal cysts)
• Inhabitants or immigrants from southeast Asia

Caroli Disease

• Considered type V choledochal cyst in new classification: Saccular dilatation of intrahepatic bile ducts with intervening normal caliber bile ducts
• Autosomal recessive disorder resulting from ductal plate malformation of large intrahepatic bile ducts
• CECT: Multifocal cystic dilatation of the biliary tree with central dot sign (enhancing portal vein radicles indenting cystic spaces)

Pancreatic Pseudocyst or Pancreatic Cystic Neoplasm

• May abut duodenum or CBD and mimic type II or III cyst
• Key to diagnosis is lack of communication with CBD and identifying site of origin in pancreas

Duodenal Diverticulum

• Diverticulum from 2nd/3rd portions of duodenum should be differentiated from type III choledochal cysts, which arise within duodenal wall and directly communicate with CBD

Simple Hepatic Cysts

• Do not communicate with biliary tree (unlike type IV or V choledochal cysts with intrahepatic involvement)
• May be extensive with polycystic hepatorenal syndrome and superficially resemble type V cysts

PATHOLOGY

General Features

• Etiology

image No consensus on etiology, but several hypotheses

– Congenital ductal plate malformation
– Anomalous junction of CBD and pancreatic duct proximal to duodenal papilla forming long common channel

image Higher pressure in pancreatic duct and absent ductal sphincter
image Free reflux of enzymes into CBD causes weakening of CBD wall and subsequent dilatation
image 60-90% of patients with choledochal cysts (especially type I and IV) have anomalous pancreaticobiliary junction
– Increased pressure in biliary tree due to webs or sphincter of Oddi dysfunction
• Associated abnormalities

image Gallbladder: Aplasia or double gallbladder
image Biliary anomalies, including biliary atresia (usually of distal biliary tree) or stenosis
image Other forms of fibropolycystic disease, including congenital hepatic fibrosis and biliary hamartomas
image Annular pancreas

Staging, Grading, & Classification

• Classification of APBJ

image Type P-B: Perpendicular insertion of pancreatic duct into CBD (fusiform)
image Type B-P: Perpendicular insertion of CBD into pancreatic duct (cystic)
image 2 major duct unions are associated with type I choledochal cyst
• Classification according to angle of ductal union

image Right-angled union: Cystic dilatation of CBD
image Acute-angled union: Fusiform dilatation of CBD

Gross Pathologic & Surgical Features

• Cystic/fusiform dilated sac with bile, stones, or sludge
• Long ectatic common channel with pancreatic duct

image Normal length: 0.2-1.0 cm; average: 0.5 cm

Microscopic Features

• Widespread ulceration and denuded mucosa in dilated CBD
• Thickened ductal wall consists of chronic inflammatory cells and fibrous tissue

CLINICAL ISSUES

Presentation

• Most common signs/symptoms

image Classic triad of symptoms (most common in children): Recurrent RUQ pain, jaundice, and palpable mass
image Infants: Intermittent jaundice and abdominal mass
image Children and adults: Intermittent fever, vomiting, jaundice, pain, and pruritus

– Symptoms related to cholangitis, pancreatitis, and gallstones

Demographics

• Age

image Can present from birth to old age, but usually diagnosed in infancy and childhood

– 80% are diagnosed in childhood; of these, 25% are detected before age 1, and 60% present before age 10
– Only 20% are diagnosed in adults
• Gender

image M:F = 1:4
• Epidemiology

image Prevalence: 1:13,000 admissions and 1:150,000 people
image Strong predominance in Asian populations

Natural History & Prognosis

• Complications

image Stone formation most common complication (within cyst itself, gallbladder, intrahepatic ducts, or pancreatic duct)

– Intrahepatic stones are common (∼ 25%) in patients with intrahepatic cysts
image Recurrent cholangitis or cholecystitis
image Recurrent or chronic pancreatitis (possibly due to anomalous pancreaticobiliary junction)
image Large cysts may rupture (extremely rare and reported only in infants) and cause bile peritonitis
image Secondary biliary cirrhosis due to long-standing biliary obstruction or repeated bouts of cholangitis
image Malignant degeneration: Most commonly cholangiocarcinoma or gallbladder cancer

– True risk of malignancy unknown, but increased risk primarily with type I or IV cysts

image Incidence of malignancy reported as 10-30% with increased risk in older patients
– Increased risk of malignancy possibly attributable to pancreaticobiliary reflux secondary to APBJ
– Risk persists in intrahepatic ducts even if extrahepatic choledochal cyst has been resected, necessitating long-term surveillance
• Prognosis

image Usually good after surgical repair
image Poor if malignant degeneration occurs

Treatment

• Treatment varies depending on type of choledochal cyst

image Type I and IV cysts: Surgical excision and reconstruction by Roux-en-Y hepaticojejunostomy due to risk of malignancy and complications (e.g., stones, cholangitis)
image Type II cysts: Surgical excision of diverticulum
image Type III cysts: May or may not be treated in asymptomatic patients due to perceived lower risk of malignancy

– Symptomatic choledochoceles often treated with endoscopic resection
image Choledochal cysts with intrahepatic involvement (types IV or V): Conservative management with possible need for liver transplantation in some patients

DIAGNOSTIC CHECKLIST

Consider

• Rule out other conditions that can cause marked biliary dilatation

Image Interpretation Pearls

• MRCP or ERCP: Cystic or fusiform dilation of bile ducts without obstructing lesion
image
(Left) Coronal volume-rendered CECT in a newborn demonstrates massive dilatation of the extrahepatic duct image, with a lesser degree of dilatation of the intrahepatic ducts image, compatible with a type IVa choledochal cyst.

image
(Right) Coronal MRCP MIP reconstruction in a young child nicely demonstrates massive dilatation of the extrahepatic duct image, as well as focal cystic dilatation of the left hepatic duct image, compatible with a type IVa choledochal cyst.
image
(Left) Coronal MRCP shows massive dilation of the intrahepatic and proximal extrahepatic bile ducts image with a sudden transition to a normal distal bile duct image. This is a type IVa choledochal cyst.

image
(Right) Ultrasound image demonstrates a cystic mass image with internal debris image arising in the porta hepatis. Note that the cyst communicates with mildly dilated intrahepatic ducts image, compatible with a choledochal cyst (probably type IVa).
image
(Left) Axial CECT shows a huge laminated stone image within a type IV choledochal cyst, with marked dilation of the intrahepatic image and extrahepatic ducts (better seen on other sections).

image
(Right) Axial CECT in the same patient shows an enhancing mass image arising from the wall of the choledochal cyst. Both stones and cholangiocarcinoma are recognized complications of longstanding choledochal cysts.
image
MRCP shows a type IVa choledochal cyst with fusiform dilatation of the intra- and extrahepatic bile ducts and abnormal entrance of the CBD into the pancreatic duct image.

image
Axial CECT of a type I choledochal cyst shows a markedly dilated extra- and intrapancreatic CBD image.
image
Axial CECT shows a spherical cystic lesion image within the medial wall of the duodenum, while the rest of the biliary tree was normal in this type III choledochocele.
image
Axial CECT shows a type I choledochal cyst with cholangiocarcinoma. Note the dilated CD image with irregular wall thickening and a mass image invading the adjacent liver.
image
Coronal MRCP MIP reconstruction demonstrates diffuse, fusiform dilatation of the CD image, as well as focal cystic dilatation of a segment of the left hepatic duct image, in keeping with a type IV choledochal cyst.
image
Axial CECT demonstrates focal cystic dilatation image of the extrahepatic bile duct, with subtle internal soft tissue image within the duct at this site. This was found to be a cholangiocarcinoma arising within a type I choledochal cyst.
image
Coronal MRCP MIP reconstruction demonstrates an exophytic cyst image arising adjacent to the gallbladder and abutting the proximal CD. This cyst was resected and confirmed to be type II choledochal cyst, the most rare subtype.
image
Coronal MRCP MIP reconstruction demonstrates focal cystic dilatation image of the proximal CBD, causing moderate dilatation of the upstream intrahepatic biliary tree, compatible with either a type I or IVa cyst.
image
Frontal cholangiogram in a young child demonstrates massive dilatation of the extrahepatic duct image. The intrahepatic ducts are moderately dilated image. This constellation of findings is compatible with a type IVa choledochal cyst.
image
Coronal MRCP MIP reconstruction demonstrates cystic dilatation image of the distal CBD, in keeping with a type I choledochal cyst. Type I cysts can have either a fusiform or cystic morphology.
image
Coronal T2 HASTE MR demonstrates fusiform dilatation image of the extrahepatic bile duct, in keeping with a type I choledochal cyst. Type I cysts are the most common type, accounting for 50-85% of all choledochal cysts.
image
Coronal MRCP shows diffuse fusiform dilation of the extrahepatic CD image, a type I choledochal cyst in the Todani classification. This is the most common type of choledochal cyst.
image
Film from an ERCP in the same patient shows the same fusiform dilation of the common duct with normal intrahepatic ducts. ERCP offers more detailed visualization of the ductal anatomy, but is usually redundant to MRCP, unless endoscopic intervention is being considered.
image
Coronal MRCP shows diffuse dilation of the extrahepatic CD image, plus moderate irregular dilation of the right and left main ducts, a type IVa choledochal cyst.
image
ERCP shows fusiform dilatation of CD, dilated intrahepatic bile duct, and near perpendicular entrance of CBD into pancreatic duct image, compatible with a type IVa choledochal cyst.

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