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

Background: The azygos system includes those veins which are straight in course, paravertebral in positionand not accompanied with the corresponding arteries. The azygos vein may arise as lumbar azygos veinfrom the back of inferior vena cava or by the union of right subcostal and right ascending lumbar veins. Itenters the thorax, receives lower 8 right posterior intercostal veins, superior intercostal vein, hemiazygosand accessory hemiazygos veins and ends by joining the superior vena cava. The hemiazygos vein is formedon the left in a manner similar to that of azygos vein. The aim of the present study was to investigate thevarious patterns of the azygos venous system.Methods: A total number of 30 cadavers were studied and were evaluated based on the study of Anson BJand Mcvay CB.Conclusion: Out of 30 specimens studied, 17 (56%) specimens showed normal pattern, 5 (16%) specimensshowed 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 inferiorvena cava in case of obstruction. The knowledge of various patterns could be useful for radiologists andsurgeons to prevent intra-operative hazards.