The thoracoepigastric vein is a valveless superficial venous channel running on the lateral trunk from the lateral thoracic vein (draining to the axillary vein) superiorly to the superficial epigastric vein (draining to the femoral vein) inferiorly, providing a portosystemic collateral pathway between the thoracic and abdominal superficial venous systems. It is normally not visible but becomes prominent as a collateral in superior vena cava obstruction (SVCO) and portal hypertension.
Prominent thoracoepigastric veins on the trunk are a clinical sign of SVCO: obstruction of the SVC forces venous blood from the head, arms, and upper thorax to drain inferiorly through the thoracoepigastric-epigastric-femoral pathway to reach the inferior vena cava. In portal hypertension, the caput medusae pattern at the umbilicus may connect upward through the thoracoepigastric veins. The thoracoepigastric vein is also the basis for the thoracoepigastric tube pedicle flap used in staged breast and upper extremity reconstruction.
SVC obstruction from lung cancer, lymphoma, or central venous catheter thrombosis diverts cephalic venous drainage through the thoracoepigastric collateral pathway, producing visible dilated veins running caudally on the trunk from the axilla toward the groin; the direction of flow (downward on the thorax) distinguishes SVCO from IVC obstruction where the veins run upward.
