Choledochal Cysts

I. Introduction and Epidemiology

Choledochal cysts are congenital malformations of the biliary tree, characterized by cystic dilations of the bile ducts. Although most cases present in early childhood, they can be diagnosed at any age. The incidence varies geographically:

• Western populations: ~1 in 100,000 live births
• Asian populations: ~1 in 13,000 live births

They occur more frequently in females than males and may be discovered incidentally in adults during imaging for unrelated conditions.

II. Pathogenesis

The exact cause remains unclear, but several theories exist:

• Anomalous pancreaticobiliary junction (APBJ): Allows reflux of pancreatic enzymes into the bile duct, causing inflammation, stasis, and ductal dilation.
• Biliary obstruction or sphincter of Oddi dysfunction: Leads to increased pressure and reflux.
• Congenital deficiency of ganglion cells: May impair bile flow and promote dilation.

III. Classification (image)

Choledochal cysts are classified into five main types, with Type I and Type IV being the most common.

Type I: Extrahepatic Cyst (80–90%)

• Type IA: Large saccular dilation of the common bile duct (CBD); gallbladder connects directly to the cyst
• Type IB: Focal saccular dilation of the CBD
• Type IC: Fusiform dilation of the CBD and common hepatic duct

Type II: CBD Diverticulum (~2%)

Isolated outpouching of the extrahepatic bile duct

Type III: Choledochocele

Cystic dilation of the distal CBD within the duodenal wall at the pancreaticobiliary junction

Type IV: Multiple Cysts

• Type IVA: Intrahepatic and extrahepatic ductal dilations
• Type IVB: Multiple extrahepatic ductal dilations only

Type V: Caroli Disease

Multiple intrahepatic cysts without extrahepatic involvement

IV. Clinical Presentation

Symptoms vary by age and cyst type. Classic pediatric presentation includes:

• Jaundice
• Acholic stools
• Palpable right upper quadrant mass

Other possible manifestations:

• Abdominal pain
• Cholangitis
• Pancreatitis
• Hepatitis
• Coagulation abnormalities
• Biliary peritonitis (rare, due to rupture)

In adults, up to 30% of cases are discovered incidentally. In Asian populations, choledochal cysts carry a significant risk of malignant transformation:

• ~10% by the second decade
• Up to 50% after age 60

V. Diagnosis

First-line Imaging

• Ultrasound: Often the initial and most accessible modality; considered the gold standard for early detection

Advanced Imaging

• MRCP (Magnetic Resonance Cholangiopancreatography): High sensitivity (90–100%), non-invasive, excellent for ductal anatomy
• CT Scan: Useful for anatomical detail and complications
• ERCP (Endoscopic Retrograde Cholangiopancreatography): Diagnostic and therapeutic, especially useful for Type III cysts; invasive and technically challenging in children

VI. Management

Surgical Resection

• Type I and Type IV: Complete excision of the extrahepatic cyst with hepaticojejunostomy (Roux-en-Y) or hepaticoduodenostomy
• Type II: Simple cyst excision
• Type III: Endoscopic sphincterotomy and drainage
• Type V (Caroli Disease): Segmental disease: liver resection; diffuse disease: liver transplantation

Rationale for Surgery

Prevent complications such as:

• Cholangitis
• Pancreatitis
• Biliary obstruction
• Malignant transformation (e.g., cholangiocarcinoma)

VII. Prognosis and Follow-Up

• Postoperative outcomes are generally favorable with early intervention
• Long-term surveillance is essential due to residual risk of malignancy
• Liver function tests and imaging should be monitored periodically

VIII. Conclusion

Choledochal cysts are rare but clinically significant congenital anomalies of the biliary system. Early recognition, accurate classification, and timely surgical management are critical to preventing serious complications, including malignancy. Advances in imaging and minimally invasive techniques continue to improve diagnostic accuracy and therapeutic outcomes.