Intercostal Venous Drainage

venae intercostales — systema

The posterior intercostal veins drain into the azygos venous system: the right upper two or three intercostals drain to the right superior intercostal vein (to the azygos); the left upper two or three drain to the left superior intercostal vein (to the left brachiocephalic); the remaining intercostals drain directly to the azygos (right) and hemiazygos/accessory hemiazygos (left), which then cross to the azygos via the transverse anastomotic channels. The azygos arch drains to the SVC.

Region: Chest

Clinical Relevance

Clinical Notes

The intercostal venous system is the primary collateral route in SVC obstruction and provides the pathway for metastatic spread from pelvic and abdominal organs to the thoracic spine (Batson's plexus connection). The azygos vein provides the surgical anastomosis target for oesophagogastric reconstruction when the stomach conduit cannot reach and for superior vena cava reconstruction. In coarctation of the aorta, the intercostal arteries (not veins) dilate as collaterals, but the venous system also becomes enlarged. The intercostal veins are damaged during thoracotomy and posterolateral approach to the thoracic spine.

Pathology

Common Injuries & Conditions

Intercostal Venous Collateralisation in SVC Obstruction

SVC obstruction from malignant or thrombotic causes forces the thoracic venous drainage through the intercostal-azygos system in reverse flow, producing visible engorged chest wall veins and upper body venous hypertension; endovascular SVC stenting restores direct SVC drainage and rapidly relieves venous hypertension.