Biliary Tract: Anatomy & Physiology

Normal Sizes

• CBD < 6-8 mm
  • 10 mm After Cholecystectomy
  • Increases 1 mm Every 10 Years After Age 60
• Gallbladder Wall < 4 mm
• Pancreatic Duct < 4 mm

Gallbladder Anatomy

• Structure
  • Fundus – Round Distal Projection
  • Body – Largest Portion
  • Neck – Tapered Portion Continuous with Cystic Duct
• Layers
  • Mucosa – Columnar Epithelium
  • No Submucosa
• Gallbladder Lies Beneath Liver Segments IV/V

Biliary Tract

• Left & Right Hepatic Ducts Combine to Form Common Hepatic Duct (CHD)
  • Left Haptic Duct is Longer Than Right
  • Left Haptic Duct is More Likely to Dilate in Distal Obstruction
• Cystic Duct Enters Common Hepatic Duct to Form Common Bile Duct (CBD)
  • Heister Valve – Spiral Valves in Cystic Duct with No Valve Function
• CBD & Pancreatic Duct Unite Outside Duodenal Wall
  • Traverse Wall as Single Duct
• Sphincter of Oddi
  • Muscular Fibers within Wall of Duodenum Around Ampulla of Vater
  • Components
    • Sphincter Choledochus (Sphincter of Boyden) – Encircles CBD
    • Sphincter Pancreaticus – Encircles Pancreatic Duct
      • Interlocks with Sphincter Choledochus to form Figure-of-Eight

Accessory Structures

• Rokitansky-Aschoff Sinuses
  • Epithelial Invaginations in Gallbladder Wall
  • From Increased Pressure (Chronic Cholecystitis)
• Ducts of Luschka
  • Accessory Bile Ducts in Gallbladder Fossa
  • Can Leak After Cholecystectomy

Vascular Supply

• Gallbladder
  • Cystic Artery – Off Right Hepatic Artery
    • Found in Triangle of Calot
    • Branches: Superficial & Deep
  • Cystic Vein – Into Right Branch of Portal Vein
• CBD
  • Marginal Arteries at 3-o’clock and 9-o’clock on ERCP
  • Supply
    • Lateral Portion (Proximal): Right Hepatic Artery
    • Medial Portion (Distal): GDA (Retroduodenal Branches)

Lymphatics

• Lie to the Right of CBD

Nerves

• Parasympathetics – Left Vagus Trunk (Anterior)
• Sympathetics – Splanchnic & Celiac Ganglions

Triangle of Calot

• Borders:
  • Lateral: Cystic Duct
  • Medial: Common Hepatic Duct
  • Superior: Liver
• Contents:
  • Cystic Artery
  • Node of Calot (Cystic Node)
    • First Site of Mets
• Rouviere’s Sulcus – Naturally Occurring Cleft in the Right Lobe of the Liver, Anterior to Segment 1
  • Used as Landmark to Begin Dissection of Calot’s Triangle
  • Present in 80% of Normal Livers

Aberrant Anatomy

• Biliary System:
  • Anatomic Variation Frequency: 30-40%
  • Most Variable Course: Right Posterior Hepatic Duct
  • Anomalies:
    • Trifurcation: Right Posterior Joins with Right Anterior & Left Hepatic Ducts Together (10-11%)
    • Crossover Anomaly: Right Posterior Joins with Left Hepatic Duct (11-15%)
      • Most Common Anomaly
    • Other Anomalies:
      • Right Posterior Joins with Common Hepatic Duct (6%)
      • Right Posterior Joins with Cystic Duct (2%)
      • Right Hepatic Duct Drains into the Cystic Duct
      • Accessory Hepatic Ducts
    • *Multiple Different Classification Systems with Different Types Have Been Proposed
• Vascular System:
  • Cystic Artery Origin Variations: Common Hepatic, Gastroduodenal or SMA
  • Double Cystic Arteries Seen in 10%