Study of Various Patterns of Azygos Venous System and its Clinical Significance

Abstract

Background: The azygos system includes those veins which are straight in course, paravertebral in position
and not accompanied with the corresponding arteries. The azygos vein may arise as lumbar azygos vein
from the back of inferior vena cava or by the union of right subcostal and right ascending lumbar veins. It
enters the thorax, receives lower 8 right posterior intercostal veins, superior intercostal vein, hemiazygos
and accessory hemiazygos veins and ends by joining the superior vena cava. The hemiazygos vein is formed
on the left in a manner similar to that of azygos vein. The aim of the present study was to investigate the
various patterns of the azygos venous system.
Methods: A total number of 30 cadavers were studied and were evaluated based on the study of Anson BJ
and Mcvay CB.
Conclusion: Out of 30 specimens studied, 17 (56%) specimens showed normal pattern, 5 (16%) specimens
showed caterpillar pattern and rest 8 (26%) specimens showed ladder pattern.
Azygos system of veins serve as an alternative drainage channel between superior vena cava and inferior
vena cava in case of obstruction. The knowledge of various patterns could be useful for radiologists and
surgeons to prevent intra-operative hazards.