Int J Anat Res 2014, 2(4):740-43. ISSN 2321-4287 740

CASE REPORT

ATYPIC DRAINAGE PATTERN OF POSTERIOR INTERCOSTAL VEINSINTO THE AZYGOS VENOUS SYSTEMRimpi Gupta *1, Deepak Goyal 2, APS Batra 3, Shveta Swami 4.

ABSTRACT

Address for Correspondence: Dr. Rimpi Gupta, MBBS, MS Anatomy, Assistant professor, Dept. ofAnatomy, BPS GMC For Women, Khanpur Kalan, Sonipat, India. E-Mail: dr.rimpigupta15@gmail.com

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*1 Assistant professor, Dept of Anatomy, BPS GMC For Women, Khanpur Kalan, Sonipat, India.2 Medical officer HCMS-1, PHC Dubheta,Dist Sonepat, Haryana, India.3 Professor & Head, Dept of Anatomy, BPS GMC For Women, Khanpur Kalan, Sonipat, India.4 Associate professor, Dept of Anatomy, BPS GMC For Women, Khanpur Kalan, Sonipat, India.

The azygos venous system vary greatly in their mode of origin, course,tributaries, anastomoses and terminationwhich resulst predominantly due to its complex embryological development. Azygos venous system develops asright and left azygos venous lines. Right azygos venous line develops into vertical part of azygos vein whereasthe left one develops into accessory hemiazygos and inferior hemiazygos veins. These are connected bysubcentral/ transvertebral veins. In the present case, we found an atypic drainage pattern of posterior intercostalveins into azygos venous system, left being more variable. Right superior intercostal vein formed by 2nd and 3rd

posterior intercostal veins whereas left superior intercostal vein was found to be absent. 2nd, 3rd, 4th & 5th leftposterior intercostal veins thus drained into accessory hemiazygos vein. Sixth and seventh left PICVs formed acommon trunk with accessory hemiazygous vein and drained into the azygous vein at T6 level. Eighth one unitedwith the hemiazygos vein and formed a common trunk which drained into azygos vein at T8 level. Such variationsof the azygos venous system are important for a clinician during mediastinal surgeries to prevent inadvertenthemorrhagic complications.KEY WORDS: Azygos vein, accessory hemiazygos vein, hemiazygos vein, superior intercostal vein.

INTRODUCTION

International Journal of Anatomy and Research,Int J Anat Res 2014, Vol 2(4):740-43. ISSN 2321- 4287

DOI: 10.16965/ijar.2014.537

Received: 13 Nov 2014Peer Review: 13 Nov 2014 Published (O):31 Dec 2014Accepted: 02 Dec 2014 Published (P):31 Dec 2014

International Journal of Anatomy and ResearchISSN 2321-4287

www.ijmhr.org/ijar.htm

DOI: 10.16965/ijar.2014.537

Variations related to azygos venous system arenot rare [1]. They vary much in their mode oforigin, course, tributeries, anastomosis andtermination. Azygos veins are important caval-caval and portocaval junctions, thus formingcollateral circulation in caval vein occlusion andin portal hypertension [2]. Several variations arereported in the literature viz agenesis of acces-sory hemiazygos vein with a predominant leftsuperior intercostal vein draining the upperintercostals spaces, agenesis of hemiazygos

vein [3], variant accessory hemiazygos vein withpersistant cranial segment of posterior cardinalvein, incomplete accessory hemiazygos veinwith posterior intercostals veins drainingbilaterally into the azygos vein [5], pre-aorticinterazygos vein [6] etc. Deviation in thepattern of azygos venous system result predomi-nantly due to its complex embryologicaldevelopment [1,7,8,9]. It is important to reportand document the different variations of theazygos venous system because especially in CTand MRI scans some variations of the azygos

Int J Anat Res 2014, 2(4):740-43. ISSN 2321-4287 741

Rimpi Gupta et al.. ATYPIC DRAINAGE PATTERN OF POSTERIOR INTERCOSTAL VEINS INTO THE AZYGOS VENOUS SYSTEM.

venous system can easily be confused withpathological conditions such as aneurysms,tumors and enlarged lymph nodes [3]. Finally, itis of utmost importance for surgeons to keep inmind the possibility of a variation of the azygosvenous system during the mediastinal opera-tions.

CASE REPORT

During the routine undergraduate dissection ofthe posterior mediastinum of 55 year old malecadaver, we encountered an unusual variationin the drainage pattern of posterior intercostalveins (PICVs), left being more variable in theirmode of drainage. In the present case, the rightsecond and third PICVs formed the superior ICVand drained into the arch of the azygos veinwhereas the fourth PICV drained directly into theazygous vein. Then five to eleven right PICVsfollowed the normal pattern of drainage into the

azygous vein. Left PICVs showed much variationin their mode of drainage. Left superior ICV wasfound to be absent. The second and third PICVswhich normally joins to form left superior ICVdrained independently into the accessoryhemiazygous vein. Fourth and fifth left PICVsdrained normally into the accessoryhemiazygous vein. Then the sixth and seventhleft PICVs formed a common trunk which joinedthe accessory hemiazygous vein and thiscommon channel drained into the azygous veinat T6 level. Eighth left PICV instead of draininginto accessory hemiazyos vein united with thehemiazygos vein and formed a common trunkwhich then drained into azygos vein at T8 level.Ninth, tenth and eleventh left PICVs followednormal pattern of drainage into the hemiazygosvein. The first PICVs of both sides drainednormally into the brachiocephalic veins ofeither side.

Fig. 1: Right azygos venous system in present case. Fig 2: Accessory hemiazygos vein in the present case.

Right SICV

Right Sympathetic chain

Arch of Azygos vein

Azygos vein

Accessory hemiazygos vein

2nd left PICV

3RD left PICV

4TH left PICV

5TH left PICV

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Rimpi Gupta et al.. ATYPIC DRAINAGE PATTERN OF POSTERIOR INTERCOSTAL VEINS INTO THE AZYGOS VENOUS SYSTEM.

Fig. 3: Drainage pattern of 6th to 11th left posteriorintercostals veins (PICVS).

Common trunk formed by acc

hemiazygos & 6th, 7th left PICVs.

Common trunk formed by 8th PICV &hemiazygos vein.

DISCUSSION

The azygos venous system develops from a pairof longitudinal venous lines, called the right andleft azygos venous line (medial sympathetic veinline), dorsolateral to the aorta. On each side,the azygos venous line lies parallel to anothertwo parallel primitive venous lines called theright and left subcardinal and post cardinalveins. The right azygos venous line develops intothe vertical part of the azygos vein. The arch ofthe azygos is contributed partially by thepersistent cephalic part of the right posteriorcardinal vein. The caudal end of each azygosvenous line joins with the corresponding sub-cardinal vein close to the level of the intersubcardinal anastomosis. Thus the azygos veinbegins as the ascending lumbar vein on bothsides. The fate of the left azygos venous line isdifferent. Due to the development of an oblique

communication between the right and the leftanterior cardiac veins, the distal part of the leftanterior cardinal vein, the cranial part of the leftposterior cardinal vein and the left commoncardinal vein regress greatly. The first of the twostructures mentioned above persist in the adultlife as left superior intercostal vein. The leftazygos venous line gives rise to a set oflongitudinally arranged veins. The upper set,named the superior or accessory hemiazygosveins, drain the fourth to the sixth intercostalsspaces posteriorly. The lower part of the azygosvenous line gives rise to the inferior hemiazygosvein that arises as the left ascending lumbarvein, similar to the azygos vein on the right,draining the seventh and lower intercostalsspaces. The accessory hemiazygos and thehemiazygos veins usually are independentsystems and connect to the azygos vein with twotransversely oriented veins at the levels of theseventh and eighth thoracic veretebrae. Thesetransverse channels embrylogically are derivedfrom such connections between the right andthe left posterior cardinal veins [10].In the present case, the distal part of the leftanterior cardinal vein, the cranial part of the leftposterior cardinal vein which normally persistas left superior intercostal vein did not persistleading to the non- formation of left superiorintercostal vein. Hence, the second and third leftPICVs drained into accessory hemiazygos vein.

CONCLUSION

Though the anatomical variations in the azygossystem are physiologically normal, it isimportant to be aware of the unique yet normalvariations of the azygos venous system duringmediastinal surgeries to prevent inadvertenthemorrhagic complications [11]. Confusion canbe avoided in diagnosing these structures afterdetection in scans and MRI [12,13].

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[2]. Arslan G, Cubuk M, Ozkaynak C, Sindel T, Luleci E.Absence of the azygos vein. Clin Imaging. 2000; 24:157–158.

Conflicts of Interests: None

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Rimpi Gupta et al.. ATYPIC DRAINAGE PATTERN OF POSTERIOR INTERCOSTAL VEINS INTO THE AZYGOS VENOUS SYSTEM.

How to cite this article:Rimpi Gupta, Deepak Goyal, APS Batra, Shveta Swami. ATYPICDRAINAGE PATTERN OF POSTERIOR INTERCOSTAL VEINS INTOTHE AZYGOS VENOUS SYSTEM. Int J Anat Res 2014;2(4):740-743. DOI: 10.16965/ijar.2014.537

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