Study of anatomical variations in the azygous venous system in human cadavers

Objectives Several variations have been reported in the azygous venous system (AZV) earlier, e.g., agenesis of azygous and hemi-azygous veins (HMAZV), incomplete accessory HMAZV, and accessory HMAZV may join the HMAZV. These variations can mimic pathologies such as aneurysms, tumors, and lymphadenopathies. The possibility of the above variations should be considered while carrying out mediastinal operations. Keeping in view the above-mentioned variations & their clinical relevance, we aimed to conduct a study to observe the course, tributaries, pattern of drainage, and termination of the azygous venous system. Material and Methods The study was carried out on 20 human adult cadavers irrespective of age and sex. The cadavers were preserved in formalin, and standard dissection steps were followed to open the posterior mediastinum. Results In the present study, five cadavers (25%) showed variations in the AZV pattern. Of the five, four (20%) were type 2 (transition), which further consists of groups 2-10. Each case showed a different type of drainage pattern & fell into group 2, 6A, 7, and 4. Variations found in Case no. 5 were not reported in previous literature, hence labeled as an atypical case. No case in the present study fits into types 1 and 3. Among the five cases, case no. 3 presented a rare variation as the 8th and 10th left posterior intercostal veins (LPICVs) bifurcated and formed two anastomotic venous rings in front of the lower thoracic vertebrae. Further, 20% of the cases showed an absence of the superior intercostal vein (SICV), 10% each on the right and left sides. Conclusion Our study has demonstrated the possible variations in the AZV system, which are to be considered during any mediastinal surgery.