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TRIBUTARIES OF AZYGOS D. Radhika1, B. Vijaya Nirmala2, G. Kanchana Latha3

1Associate Professor, Department of Anatomy, Guntur Medical College, Guntur, Andhra Pradesh. 2Assistant Professor, Department of Anatomy, Guntur Medical College, Guntur, Andhra Pradesh. 3Professor & HOD, Department of Anatomy, RIMS, Kadapa, Andhra Pradesh.

ABSTRACT INTRODUCTION Azygos system of taken out for study because its nearness to viscera-like intrathoracic course of esophagus, aorta, heart, lungs and its intimate relationship with contents of posterior mediastinum. Azygos system includes Azygos vein and accessory Azygos vein and . The present study carried out on hundred cadavers, out of which foetus 10, children 8, adults 82, in three years span in RIMS Medical College, Kadapa. Their formation, course, relations, termination, their tributaries and communications are explored. Different variations are observed. Knowledge of such variations and drainage pattern is significant in abdominal surgeries also plays an important role in CT and MRI studies on posterior mediastinum. Variations in Azygos system also useful for thoracic surgeon because its vulnerability to damage during the surgical procedures, injuries, firearm wounds.

KEYPOINTS Azygos system of veins, Tributaries, Variations, Posterior Mediastinum.

HOW TO CITE THIS ARTICLE: Radhika D, Nirmala BV, Latha GK. Tributaries of azygos vein. J Evid Based Med Healthc 2016; 3(1), 49-51. DOI: 10.18410/jebmh/2016/11

INTRODUCTION: Study of Azygos system is useful because drains 4th-11th intercostal spaces directly and 2 and 3rd spaces of its nearness to surrounding viscera-like intrathoracic through superior intercostal vein. course of esophagus, aorta, heart, lungs and intimate relationship to contents of mediastinum. It is also in MATERIAL AND METHODS: Cadavers’ of still-born fetuses, relationship with thoracic duct. Both of them are vulnerable adult cadavers received to Department of Anatomy for to many numbers of variations in its origin, course, level of dissection purpose fixed by 10% formalin. Total 100 anastomosis and its termination. Azygos system consists of specimens dissected through anterior abdominal wall. asymmetrical pair of veins on either side of anterolateral Relations of azygos vein with surrounding structures were aspects of vertebral column mainly right and left part. Right observed. one is longest and largest part azygos system of veins. Inferior part of left compliment is Hemiazygos and the RESULTS: Azygos vein formed by right ascending lumbar superior part being named as Accessory Hemiazygos. vein and right subcostal vein at the level of 12th thoracic Hemiazygos vein formed by the union of right subcostal and vertebra in 88% of cases (Figure 1). Azygos vein formed by right with a channel from dorsal only subcostal vein in 12% of cases (Figure 2). Azygos vein aspect of inferior vena cava about the level of renal veins. in its upward course in posterior mediastinum left side This venous trunk enter the thorax by passing through aortic deviation is described in elderly 45 to 70 years, changes are opening of diaphragm.(1) and may pass through right crus or equal in both sexes that is 66.66%- (Figure 3) Termination of behind it.(2) At level of 4th thoracic vertebra it forms an arch azygos vein varying considerably in children, fetuses and near root of right lung end in superior vena cava. It is joined adults. It is varying from 3rd to 5th thoracic vertebra. Azygos by hemiazygos veins at 8th thoracic vertebra and accessory vein ended at level of 3rd thoracic vertebra 8% of subjects Hemiazygos vein at 7th thoracic vertebra. Superior and and 4th thoracic vertebra 85%, 5th thoracic vertebra 7% of Inferior Hemiazygos veins are left compliment of Azygos vein subjects. partly overlapped by descending thoracic aorta. Hemiazygos vein–formed entering into thorax passes through left crus of Hemiazygos Veins and Accessory Hemiazygos: diaphragm. It ascends up anterolateral part of vertebral Hemiazygos vein crossing midline towards right side towards column up to level of 8th thoracic vertebra cross midline joins right side at level of 8th thoracic vertebra and accessory vein azygos vein. Accessory Hemiazygos vein–inconstant length at 7th thoracic vertebra–85% objects. Hemiazygos vein broken into 2 channels in 9 subjects 3 channels in 6 subjects. Submission 18-12-2015, Peer Review 19-12-2015, Hemiazygos is directly continuous with accessory hemiazygos Acceptance 28-12-2015, Published 04-01-2016. both of them ending in azygos vein by single common retro- Corresponding Author: aortic channel (Figure 4). Dr. D. Radhika, C/o Dr. A. Laxmi, Multiple variations in left venous channels seen in one Flat no. 401, Harivillu Residency, specimen (Figure 5). Pattabhipuram 2nd Lane, Guntur-6. a) Formation of superior intercostal vein by union of 2nd and E-mail: [email protected] rd th DOI: 10.18410/jebmh/2016/11 3 to join azygos vein at level of 4 thoracic vertebra.

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Jebmh.com Original Article b) Formation of Accessory hemiazygos vein by 4 to 7 intercoastal veins. c) Formation of Hemiazygos vein 8-11 intercostal veins. d) Vertical anastomosis of Hemiazygos vein and accessory Hemiazygos. e) A post-aortic anastomotic channel between junction of accessory Hemiazygos and Azygos veins. At 5th thoracic vertebra. f) Saccular dilatation of Hemiazygos and accessory Hemiazygos vein joins with azygos vein at 7th thoracic vertebra.

Fig. 3: Communication of hemi-azygos vein and azygos vein with multiple channels

Fig. 1: Azygos vein formed by right ascending lumbar vein and right subcostal vein at the level of 12th thoracic vertebra Fig. 4: Hemiazygos and accessory hemiazygos communicating azygos vein with single aortic channel

Fig. 2: Formation of azygos vein by subcostal

Fig. 5: Multiple variations of left venous channel

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Jebmh.com Original Article

Total connects hemiazygos and accessory hemiazygos vein Number Formation of remainder of left and right posterior cardinal veins.(5) Deviation Termination of Azygos Vein Hemiazygos–Hemiazygos vein ends at level of 8th thoracic Cases vertebra to join Azygos vein may join with additional 4th thoracic transverse branches below the level of its ending and found Ascending lumbar Left side vertebra -85 2 or more braches in 12.5%.(6) 100 and right deviation- 3rd thoracic In our study, crossing midline at 8th thoracic vertebra in subcostalvein-88 66.66 vertebra-8 70% of subjects and 9th thoracic vertebra in 3% of subjects. Only subcostal No deviation- 5th thoracic Normal ending by single channel of vertical anastomoses with

vein-12 33.34 vertebra hemiazygos and accessory Hemiazygos in 12% of subjects. 5) Table 1: Azygos Vein Hemiazygos ending in multiple channels in 15%. We got multiple variations in 1 case of 100 studies fig- multiple channels–3 transverse post-aortic channels Accessory Variations Hemiazygos Vein Hemiazygos Vein communicating the accessory hemiazygos and Azygos vein. 7th thoracic A case of multiple abnormalities of azygos system Ending 8th thoracic vertebra-70 vertebra-70 reported by Pyrozwiski et al. reported in the 76 old Caucasian 9th thoracic th th 9th thoracic vertebra-3 male, interazygos vein formed by 9 and 11 left posterior vertebra-3 intercostal veins and 7th and 8th by left intercostal veins.(6) Vertical 12 cases 12 cases anastomosis CONCLUSIONS: The isolated anomalies of azygos Ending in multiple 14 cases 14 cases hemiazygos/accessory hemiazygos veins are very rare. They channels are invariably associated with anomalies of lymphoid tissue Table 2: Hemiazygos vein and and polysplenism are associated anomalies of superior vena accessory hemiazygos vein-100 cases cava. It is very important to identify variations in azygos system, especially CT of mediastinum easily confused with Multiple variations in left venous channels-1 case. Aneurism and lymphadenopathy. Anomalies of venous system are well known and they are DISCUSSION: Azygos vein typically receives all right the detected during surgeries, Haemorrhage is one of the intercostal spaces, whether directly or indirectly lower common complication. Knowledge of such variations are very intercostal veins tend to enter segmental fashion though 2 useful for surgeons operating on posterior mediastinum. successive veins may fuse to form a common stem.(3) drains intercostal spaces. Its arched portion is joined by superior REFERENCES: intercostal vein usually drains 2nd and 3rd intercostal spaces. 1. Hamilton Boyd JD. Text book of human anatomy, Vivid analysis of sibs work in 1934 is given by Hollinshed, 1958;1st edition:375. right subcostal vein joining ascending lumbar vein in 94%, 2. Susan Standring, Neil R Borley, Patricia Collins alan r remaining 6% only by right subcostal vein. In our work 88% crossman. Grays Anatomy. 2008;40th edition:91. of cases formed by right subcostal vein and right ascending 3. Henry Hollin Shed. Anatomy for surgeons. lumbar vein, whereas subcostal vein in 12% of subjects. 1961;2(73):188. Kangami and Sakai 1990 investigated the deviation of 4. Kangami and Sukai, Okajimas, Folia. Anatomy. Jap Aug Azygos vein in posterior mediastinum, crossing of azygos in 1990;67(2-3):11-14. midline in 84.7%, ascending in midline 11.5% in one body 5. Srinivas Rao, Arindom banerjee. Anatomical variations ascending in right side. Probably aging process contributes of the azygos venous system. International journal of deviation to left side of mediastinum.(4) biomedical & research Res. 2014;5(4):4535-4538. Knowledge of development of Azygos system is necessary 6. Pyrozwiski J, Spondnik JH, Lewicka A, et al. A case of to understand variations. Azygos venous system generates multiple abnormalities of the azygos venous system: a from subcardinal vein. Rt. cardinal vein develops into Azygos praeaortic interazygos vein. Folia Morphol (Warsz). Nov vein. Lt. Cardinal Vein develops into hemiazygos. Left 2007;66(4):353-5. superior intercostals vein and accessory hemiazygos vein derived from left posterior cardinal vein. The part that

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