The HV drained the lower four left posterior intercostal veins in 33 % of cadavers, with its termination being between T6 and T10.
The right superior intercostal vein drained the upper four right posterior intercostal veins into the AV in 30 % of cadavers.
The AV may have one or more origins, but usually drains the lower eight right posterior intercostal veins directly, as well as the right superior intercostal vein, which in turn drains the four upper right posteriorintercostal veins.
In one type 2A a long vein was observed to communicate with the left superior intercostal vein and then descend to receive tributaries from the 4th to 9th left posterior intercostal veins: it terminated by joining the HV at the level of T10-T11 after crossing anteriorly to the 10th left posterior intercostal vein.
This could be due to the HV also receiving blood from the abdomen and lower left posterior intercostal veins. In 46 % of cadavers the AHV communicated with the left superior intercostal vein, which probably received some middle left posterior intercostal veins that normally drained into the left brachiocephalic vein.
Intervertebral veins directly connecting the vertebral venous system to the azygos venous system rather than the proximal end of the posterior intercostal veins. Rev.
These communications drain the left posterior intercostal veins through a venous plexus located on the lateral aspect of the vertebral column.
Type 2E with more than five retroaortic communications draining the left posterior intercostal veins after forming a plexus on the lateral aspect of the vertebral column.
Below this level the AV and HV drained the right and left posterior intercostal veins respectively.
In 53 % of cadavers the left superior intercostal vein communicated with the azygos system, either directly without communicating with the AHV (7 % of cadavers) or via the AHV with or without communicating with the AV (46 % of cadavers): it drained into the left brachiocephalic vein in all cadavers.