Improperly placed venous cannula blocks which vessel?

• A. Portal vein
• B. Inferior vena cava
• C. Renal vein
• D. Hepatic vein

Answer: (D)

When a venous cannula is placed improperly into a hepatic vein, it can block the liver’s outflow. The hepatic veins are the vessels that drain blood from the liver into the inferior vena cava (IVC) just below the diaphragm. If the cannula occludes a hepatic vein, hepatic venous drainage is impeded, causing blood to back up in the liver and impair hepatic perfusion during perfusion or bypass.

Blocking the portal vein would affect inflow to the liver rather than its outflow, so it’s not the vessel whose obstruction is most likely from a misplaced venous cannula. The renal veins drain the kidneys into the IVC and are not directly involved in draining the liver. The IVC would affect systemic venous return broadly, but the question targets the specific hepatic drainage pathway, which is the hepatic vein.