Unit
- Liver lobes: The liver is divided into right and left lobes by the falciform ligament. The right lobe is larger and includes the caudate and quadrate lobes as anatomical subregions important for surgical planning.
- Segmental anatomy (Couinaud): The liver is divided into eight functional segments, each with independent vascular inflow, outflow, and biliary drainage. Segment identification guides precise resection boundaries.
- Portal vein: The portal vein supplies approximately 75% of hepatic blood flow, delivering nutrient-rich blood from the gastrointestinal tract. It branches into left and right main trunks before segmental division.
- Hepatic artery: The proper hepatic artery provides the remaining 25% of blood flow, carrying oxygenated blood. Variations in origin and branching are common and must be identified preoperatively.
- Hepatic veins: Three major hepatic veins (right, middle, left) drain into the inferior vena cava. The middle hepatic vein serves as the boundary between right and left hemi-livers.
- Biliary tree: Bile flows from hepatocyte canaliculi through bile ducts in each segment, converging into right and left hepatic ducts, then the common hepatic duct. The cystic duct joins to form the common bile duct.
- Ligamentous attachments: The liver is stabilized by the coronary, falciform, triangular, and hepatogastric ligaments. These structures contain vessels that must be controlled during mobilization.
- Lymphatic drainage: Hepatic lymph drains to hilar, celiac, and para-aortic nodes. Understanding drainage patterns helps in staging malignancies and predicting spread.
- Gallbladder and cystic duct: The gallbladder lies in the fossa between the right and quadrate lobes. The cystic duct joins the common hepatic duct to form the common bile duct. Variant insertions, such as a low or posterior joining, occur in up to 20% of patients and must be identified on preoperative imaging to avoid intraoperative complications. The cystic artery typically arises from the right hepatic artery but may have aberrant origins that require careful dissection.
- Hilar plate anatomy: The hilar plate is the dense fibrous sheath containing the bile ducts, portal veins, and hepatic arteries at the porta hepatis. Dissection of the hilar plate allows safe identification and isolation of these structures for individual ligation during hepatectomy. The plate is continuous with the Glissonian sheath extending into the liver along portal triads. Understanding its relationship to the caudate lobe and segment I is essential for hilar dissection and control of inflow vessels; variations require careful intraoperative assessment.
- Accessory hepatic veins: In addition to the three major hepatic veins, small accessory veins frequently drain directly from the caudate lobe or right posterior segments into the retrohepatic vena cava. These veins are often encountered during mobilization of the liver and must be identified and controlled to avoid avulsion and hemorrhage. Preoperative identification on cross-sectional imaging helps plan the surgical approach, particularly in living donor hepatectomy where preservation of accessory veins may be necessary.
- Pringle maneuver: The Pringle maneuver involves temporary occlusion of the portal vein and hepatic artery within the hepatoduodenal ligament to control inflow during parenchymal transection. This technique reduces blood loss but induces ischemic injury; intermittent clamping with short reperfusion intervals of five to ten minutes is standard practice to minimize damage, especially in patients with underlying liver disease. Total clamp time should be limited, and the maneuver remains a cornerstone of hepatic resection surgery.
Scope of Practice
Role: Hepatobiliary Surgeon
Within scope:
- Interpreting cross-sectional imaging to identify segmental anatomy and vascular variations before surgery
- Performing anatomical resections based on Couinaud segments to preserve functional parenchyma
- Identifying and controlling hepatic vessels during open and laparoscopic procedures
Outside scope:
- Diagnosing hepatic parenchymal disease beyond surgical context; requires hepatologist
- Performing liver transplantation without specialized fellowship training
- Interpreting intraoperative cholangiography independently; requires radiologic consultation for complex cases
Quick Revision
- The liver has two lobes and eight Couinaud segments, each with independent vasculature.
- Portal vein and hepatic artery supply dual blood flow; hepatic veins drain to IVC.
- Biliary drainage follows segmental anatomy; variations require preoperative mapping.
- Ligaments and lymphatics are critical for surgical mobilization and cancer staging.
Disclaimer
Educational use only. Not intended for practical surgery, incisions, or other surgical procedures. It does not qualify you to perform physical operations.