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Choledochal Cysts and Anomalous Pancreaticobiliary Union

Overview

Choledochal cysts are uncommon anomalies of the biliary tree characterized by cystic dilation of the intrahepatic or extrahepatic bile ducts (or both). They are often associated with an anomalous pancreaticobiliary union (APBU), especially in Asian populations, which can lead to complications such as pancreatitis and an increased risk of carcinoma.

Classification (Todani Classification)

Choledochal cysts are classified according to the scheme proposed by Todani et al.:

  1. Type I (80–90%): Involves only the extrahepatic biliary tree.
    • Type Ia: Cystic dilation of the entire extrahepatic bile duct.
    • Type Ib: Focal segmental dilation.
    • Type Ic: Fusiform dilation.
  2. Type II (2%): Extrapancreatic bile duct diverticulum.
  3. Type III (1.4–5%): Choledochoceles involving the intraduodenal part of the common bile duct (CBD).
  4. Type IV:
    • Type IV A (19%): Multiple intrahepatic and extrahepatic cysts.
    • Type IV B: Multiple extrahepatic cysts.
  5. Type V: Caroli disease—single or multiple intrahepatic cysts communicating with the biliary system.

Anomalous Pancreaticobiliary Union (APBU)

  • Definition: A common channel longer than 15 mm where the pancreatic duct and bile duct junction is outside the duodenal wall and proximal to the sphincter of Oddi.
  • Significance: Promotes reflux of pancreatic juice into the biliary tree, potentially leading to chronic inflammation and increased risk of carcinoma (2.5–17% in choledochal cyst patients).
  • Prevalence: More common in Asian populations; not always associated with choledochal cysts (22–37% cases without cysts).

Clinical Presentation

  • Symptoms in Children:
    • Recurrent abdominal pain (82%).
    • Nausea and vomiting (66%).
    • Mild jaundice (44%).
    • Abdominal mass (29%).
    • Fever (29%).
  • Classical Triad: Abdominal pain, jaundice, and abdominal mass (<20% of patients).
  • Age of Diagnosis: More than two-thirds diagnosed under 10 years; can be detected prenatally via ultrasound as early as the 15th week of gestation.

Diagnosis

Imaging Modalities

  • Ultrasound: Initial, non-invasive imaging to detect bile duct dilation.
  • Magnetic Resonance Cholangiopancreatography (MRCP):
    • Non-invasive, no radiation.
    • Assesses cyst anatomy, biliary anomalies, and complications.
  • Computed Tomography (CT):
    • High-resolution images without respiratory artifacts.
    • Multidetector CT (MD-CT) and 3D reconstructions provide detailed anatomy.
  • Endoscopic Retrograde Cholangiopancreatography (ERCP):
    • Gold standard for diagnosing choledochal cysts.
    • Invasive but allows for therapeutic interventions, especially in Type III cysts.
  • Percutaneous Transhepatic Cholangiography (PTC):
    • Used when ERCP is unsuccessful or contraindicated.

Complications

Biliary Stones

  • Prevalence: 9% in children; 24.1% in adults.
  • Locations:
    • Cholecystolithiasis (12.7%).
    • Choledocholithiasis (65.8%).
    • Hepatolithiasis (21.5%).

Pancreatitis

  • Incidence: ~30% of patients.
  • Cause: Protein plug formation leading to obstruction and increased intraluminal pressure.
  • Clinical Course: Often transient and self-limiting due to spontaneous resolution of protein plugs.

Spontaneous Perforation of the Bile Duct

  • Demographics: Mostly in children under 1 year.
  • Presentation: Bile peritonitis due to a small perforation, often on the anterior aspect of the bile duct.

Carcinoma

  • Risk Factors: Chronic inflammation from APBU and bile stasis.
  • Incidence: Ranges from 3.2% to 39.4% in choledochal cyst patients.
  • Age-related Risk:
    • <10 years: 0.7%.
    • 11–20 years: 6.8%.
    • 20 years: 14.3%.
  • Types:
    • Cholangiocarcinoma.
    • Gallbladder Carcinoma.

Management

Surgical Treatment

  • Definitive Treatment: Complete excision of the extrahepatic bile duct with Roux-en-Y hepaticojejunostomy.
  • Timing:
    • Children: Operate as soon as possible, even in neonates.
    • Adults: Immediate surgery due to increased cancer risk.
  • Type-specific Approaches:
    • Type I and IV-A: Extrahepatic bile duct excision.
    • Type II: Simple cyst excision.
    • Type III (Choledochocele):
      • Endoscopic sphincterotomy and cyst unroofing.
      • Surgical excision if endoscopic treatment fails.

Management of APBU Without Choledochal Cyst

  • Cholecystectomy: Prophylactic removal of the gallbladder due to high cancer risk.
  • Endoscopic Sphincterotomy (ES):
    • Reduces frequency of pancreatitis and abdominal pain.
    • Long-term surveillance for cancer remains unclear.

Postoperative Complications

  • Early:
    • Anastomotic leakage.
    • Bleeding.
    • Pancreatitis.
    • Ileus.
    • Pancreatic fistula.
  • Long-term:
    • Cholangitis: Due to anastomotic strictures or residual intrahepatic stones.
    • Hepatolithiasis: Requires intervention to prevent recurrent stones.
    • Carcinoma: Malignancy can still occur; lifelong follow-up is essential.

Caroli Disease (Type V)

Definition

  • Caroli Disease: Characterized by segmental, saccular dilation of intrahepatic bile ducts communicating with the biliary system.
  • Forms:
    • Simple Type: Cystic dilation without fibrosis.
    • Periportal Fibrosis Type: Associated with congenital hepatic fibrosis.

Clinical Features

  • Symptoms:
    • Recurrent cholangitis (64%).
    • Right upper quadrant abdominal pain (18%).
    • Portal hypertension (22%).
  • Complications:
    • Biliary stones.
    • Liver abscesses.
    • Cholangiocarcinoma (~7% incidence).

Diagnosis

  • Imaging:
    • Ultrasound: Detects cystic intrahepatic lesions.
    • MRCP and CT: Visualizes saccular dilations and "central dot sign" indicating portal radicles within dilated ducts.
  • Differentiation: Must distinguish from other fibrocystic liver diseases.

Management

  • Medical: Antibiotics for cholangitis; ursodeoxycholic acid for cholestasis.
  • Surgical:
    • Liver Resection: For localized disease.
    • Liver Transplantation: For diffuse disease or when complications are unmanageable.

Risk Factors for Gallbladder and Cholangiocarcinoma

  • Epidemiology:
    • Higher incidence in South America, Asia, and among Native Americans and Japanese Americans.
  • Risk Factors:
    • Chronic Inflammation: Gallstones, cholecystitis, APBU.
    • Anomalous Pancreaticobiliary Union: Increases risk for both gallbladder and bile duct cancers.
    • Chronic Infections: Liver flukes like Opisthorchis viverrini (classified as a type 1 carcinogen).
    • Lifestyle Factors: Obesity, high carbohydrate diet, alcohol, and tobacco use.

Conclusion

Choledochal cysts require prompt diagnosis and management due to the risk of severe complications, including malignancy. Surgical excision with biliary reconstruction is the standard treatment for most types, and lifelong surveillance is critical due to the potential for late complications such as carcinoma. Caroli disease, while rare, presents significant management challenges and necessitates individualized therapeutic approaches.

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