128. Anastomoses between the systems of the both venae cavae (cava-caval anastomoses).

CAVO-CAVAL ANASTMOSIS

• Large venous anastomoses are Present between the inferior and superior vena cava, on the anterior and posterior trunk walls.

Function:

Provide collateral pathways for returning venous blood to the superior vena cava and right heart atrium in patient with outflow blockage in the IVC or common iliac veins.

Anastmoses on the anterior wall of the abdomin:

1. 1. Deep pathway (posterior to the rectus abdominis):

Inferior vena cava → common iliac vein → external iliac vein → inferior epigastric vein → superior epigastric vein → internal thoracic vein → subclavian vein → brachiocephalic vein → superior vena cava.

1. 2. Superficial pathway (anterior to the rectus abdominis):

Inferior vena cava → common iliac vein → external iliac vein → femoral vein → superficial epigastric vein/superficial circumflex iliac vein → thoracoepigastric vein/lateral thoracic vein → axillary vein → subclavian vein → brachiocephalic vein → superior vena cava.

Anastmoses on the posterior wall of the abdomen:

1. 1. A direct pathway between the ascending lumbar vein and azygos/hemiazygos vein:

Inferior vena cava → (possibly via the common iliac vein) ascending lumbar vein → azygos/hemiazygos vein → superior vena cava.

1. 2. An indirect pathway between the ascending lumbar vein and azygos/hemiazygos vein by way of horizontal trunk wall veins (intercostal and lumbar veins, mediated by venous plexuses on the spinal column; for clarity, not shown here):

Inferior vena cava → (possibly via the common iliac vein) ascending lumbar vein → lumbar veins → vertebral venous plexus → posterior intercostal veins → azygos/hemiazygos vein → superior vena cava.