HEMIAZYGOYS VEIN:

It is called INFERIOR AZYGOUS VEIN  because it is the mirror image of the lower part of the   azygous vein.

formation:

it is either from the left renal vein or by the union of left ascending lumbar and left subclavian vein

.  It pierces the left crus of the diaphragm and passes left to  the vertebra. Crosses to the opposite side at the level of eigth thoracic vertebra by passing behind aorta and oesophagus and drains into azygous vein.

Tributaries:

1. Left Ascending Lumbar Vein

2. Left Subcostal Vein

3. ninth to eleventh posterior intercostal vein.