Azygos Venous System Research Articles

CT Findings of Azygos Venous System: Congenital Variants and Acquired Structural Changes.

The azygos venous system is a crucial conduit of the posterior thorax and potentially vital collateral pathway. However, it is often overlooked clinically and radiologically. This pictorial essay reviews the normal azygos venous anatomy and CT findings of congenital variations and structural changes associated with acquired pathologies.

A Case Series Cadaveric Study on Acquired and Congenital Azygos Venous System Variations

The azygos venous system holds essential clinical relevance as it can provide collateral circulation in cases where the superior and inferior vena cava become obstructed. Additionally, it is important in imaging and mediastinal procedures because variations in this system may be confused with pathology. In this study, the azygos system of 31 embalmed anatomy donors was dissected, analyzed, and classified according to the Anson McVay system and Dahran and Saomes subclassification. Out of 31 donors, one (3.22%) donor was classified as Type I, 27 (87.09%) were Type II, two (6.45%) were Type III, and one (3.22%) was unobservable. These values closely replicated values previously reported in literature; however, four subjects exhibited variations that are rare or not previously reported in literature. In this paper, we describe those rare cases and consider their development and clinical relevance.

Normal variations of the superior vena cava and azygos venous system depiction by CT scan in the adult Thai population.

Identification of normal variations to the thoracic central venous system anatomy is essential in radiological intervention and cardiothoracic surgery to prevent complications. To estimate the prevalence and pattern of normal variations of superior vena cava (SVC) and azygos venous system as well as factors associated with normal variations of SVC. Venous-phase chest CT of 1336 patients were retrospectively reviewed. Age, sex, and underlying disease were recorded. SVC diameter and cross-sectional area were measured to evaluate for associations with normal variations. The prevalence of normal anatomical variations of SVC and azygos venous system were 0.3% and 1.5%, respectively. Duplicated SVC was the most common variations. The most common variation for the azygos venous system was the connection between the hemiazygos and accessory hemiazygos veins draining into the left brachiocephalic vein (12/1336 cases, 0.9%). The median (interquartile range [IQR]) cross-sectional area compared between normal SVC (297.2 mm2) and duplicated SVC (223.5 mm2) showed a statistically significant difference (P = 0.033). This study determined the prevalence of rare normal variations of the azygos venous system, a connection between the hemiazygos and accessory hemiazygos veins draining into the left brachiocephalic vein. The prevalence of normal variations of the SVC and azygos venous system in the adult Thai population was similar with that of previous publications. Cross-sectional area was the only factor with a significant association with SVC variations.

Azygous Venous System - Anatomical Variation and Its Clinical Significance

Introduction: Azygous venous system is the system of unpaired veins comprising of the azygous vein, the hemiazygous vein and accessory hemiazygous vein1. They are para vertebral in position, provided with valves and drain most of the blood from the thoracic and posterior abdominal walls. They communicate with the venacaval system infront and vertebral plexus behind. It connects the superior vena cava with the inferior vena cava. The azygous vein is inconstant in the mode of origin. Aim: To explore the anatomical variations in the course of azygous system of veins. Material and methods: The present study was done in the Department of Anatomy, Apollo institute of Medical sciences and Research, Hyderabad over a period of 2 years. The present study was conducted on 12 cadavers (irrespective of age and sex). The course of the azygos venous system in these 12 cadavers was carefully observed and documented. Results: Anatomical variation was found in two cadavers. Discussion: The azygous system of veins arises from a pair of longitudinal venous lines called right and left azygous venous lines on each side of the aorta1. On each side of the azygous venous lines lies two parallel primitive lines called right and left sub cardinal and posterior cardinal veins. It forms an important route for collateral circulation in venacaval occlusion such as in portal hypertension. It serves as the main collateral channel to shunt the blood from the upper half of the body to the inferior venacaval in case of superior vena caval obstruction. Conclusion: Identification and understanding of these variations are important during preoperative radiological investigations and surgical procedures especially spinal surgery between T7 and T12 to avoid injury which may lead to postoperative haematomas Keywords: Azygous venous system, azygous vein, venacaval system.

Azygos Venous System Variations: A Clinical Review

Azygos Venous System Variations: A Clinical Review

Variations in Azygos Venous System in The Eastern Indian Population: A Cadaveric Study

Background: This study aimed to classify Azygos vein patterns in the Eastern Indian population. Methods: During the routine dissection of MBBS in the 2018–2020 academic year, 20 formalin embalmed cadavers aged 50–70 were used to classify the azygos system. The cadaver’s age was verified by its entry into our institute’s anatomy register. The register confirmed that all cadavers used for dissection were of Indian origin. Though gender was not compared in this study, it was noted for record purposes by identifying the external genitalia and confirming it to the records. These were the exclusion criteria: 1) No major thoracic surgeries; 2) No major thoracic deformities. Azygos, hemiazygos, and accessory hemiazygos veins were also examined. Results: The Anson & McVay system was used to classify the recruited cadavers’ azygos system. The cadavers were classified into Type-1, Type-2, and Type-3. Type 2 was again subdivided into 5 subgroups and Type-3 into2 sub-groups. In one cadaver, Type-1 was observed, 17 cadavers had Type-2 azygos system, and 2 cadavers showed Type-3. Of the 17 cadavers of Type-2, 3 and 7 cadavers had Type-2A and -2B, respectively. Similarly, 4 and 1 cadavers had 2C and 2D patterns, respectively. Also, 2 cadavers showed 2E type. Of the 2 cadavers of Type-3, one was Type -3A and one Type-3B. The termination of the azygos vein vertebral level was between T2 and T4, of the hemiazygos vein was T8 to T11, and accessory hemiazygos veins were between T7 and T10. Conclusion: These variations should be well studied to avoid misinterpretation during radiological investigations and surgical interventions. KEY WORDS: Azygos vein, Hemiazygos vein, Posterior mediastinum, Radiological investigation, Variation.

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.

Azygos Continuation of the Inferior Vena Cava: Potential for Misdiagnosis as Lung Neoplasm.

The azygos venous system is an accessory venous pathway supplying an important collateral circulation between the superior and inferior vena cava (IVC). We report a case of complicated community-acquired pneumonia with interruption of the IVC with azygos continuation that was misdiagnosed as lung neoplasm. The aim of this case report is to emphasize the importance of recognizing an enlarged azygos vein at the confluence with the superior vena cava and in the retrocrural space to avoid misdiagnosis as a right-sided para-tracheal mass. The angiographic features and clinical importance of this condition are discussed. An enlarged azygos vein at the confluence with the superior vena cava and in the retrocrural space can be misdiagnosed as a right-sided para-tracheal mass/neoplasm or retrocrural adenopathy.Biopsy is the most important tool to confirm the diagnosis of malignancy but could be catastrophic in this situation.Re-imaging after treatment for infection and pneumonia could potentially avoid this error.

The effects of maternal position, in late gestation pregnancy, on placental blood flow and oxygenation: an MRI study.

Maternal supine sleep position in late pregnancy is associated with an increased risk of stillbirth. Maternal supine position in late pregnancy reduces maternal cardiac output and uterine blood flow. Using MRI, this study shows that compared to the left lateral position, maternal supine position in late pregnancy is associated with reduced utero-placental blood flow and oxygen transfer across the placenta with an average 6.2% reduction in oxygen delivery to the fetus and an average 11% reduction in fetal umbilical venous blood flow. Maternal sleep position in late gestation is associated with an increased risk of stillbirth, though the pathophysiological reasons for this are unclear. Studies using magnetic resonance imaging (MRI) have shown that compared with lateral positions, lying supine causes a reduction in cardiac output, reduced abdominal aortic blood flow and reduced vena caval flow which is only partially compensated for by increased flow in the azygos venous system. Using functional MRI techniques, including an acquisition termed diffusion-relaxation combined imaging of the placenta (DECIDE), which combines diffusion weighted imaging and T2 relaxometry, blood flow and oxygen transfer were estimated in the maternal, fetal and placental compartments when subjects were scanned both supine and in left lateral positions. In late gestation pregnancy, lying supine caused a 23.7% (P<0.0001) reduction in total internal iliac arterial blood flow to the uterus. In addition, lying in the supine position caused a 6.2% (P=0.038) reduction in oxygen movement across the placenta. The reductions in oxygen transfer to the fetus, termed delivery flux, of 11.2% (P=0.0597) and in fetal oxygen saturation of 4.4% (P=0.0793) did not reach statistical significance. It is concluded that even in healthy late gestation pregnancy, maternal position significantly affects oxygen transfer across the placenta and may in part provide an explanation for late stillbirth in vulnerable fetuses.

An observational study on morphology of azygos vein

Introduction: Azygos system of veins comprising unpaired azygos vein and its main tributary, the hemiazygos veins. Variations have been observed in formation, course of azygos vein, also in its, tributaries and anastomoses. Objectives: To observe azygos venous system pattern. Materials: 50 embalmed human cadavers irrespective of their sex and age. Methods: Following Anson’s classification system in which azygos venous system having vertical and horizontal connections which include three basic types, primitive or embryological types, transient type, and single type as and their eleven subgroups. Results: The basic type pattern in all the specimens (100%) was transitional type. In subgroups: atypical type observed in 12 specimens (24%). group 5 & group 6B was observed in 11 specimens (22%), group 2 was observed in five specimens (10%), group 4 was observed in five specimens (10%), group 7 was observed in 3 specimens (06%), group 10 was observed in 03 specimens (06%). Conclusion: The importance’s of variations in the pattern of azygos venous system which has to be identified during computed tomography and magnetic resonance imaging of mediastinum may be confused with aneurysm, lymphadenopathy and other abnormalities like tumor. During surgery of large vessel and the mediastinal operations, these kinds of azygos venous system pattern variations have to keep in the mind. Keywords: Azygos vein, Morphology, Azygos venous system types.

An abnormal course of the interazygos vein: a case report

BackgroundThe azygos venous system in the posterior mediastinum has a complex developmental pattern.Case presentationDuring the dissection of this region, we encountered a variation in this system. In this case, we observed that the accessory hemiazygos and hemiazygos veins in the left side passed anterior to the aorta and drained to the azygos vein located on the left side of the vertebral column. Other structures were normal in this area.ConclusionsThis variation is important in mediastinal surgery and radiographic interpretation.

The Azygos Vein From A to Z.

Congenital and acquired abnormalities of the azygos vein can affect its size and position. Alteration of contrast material flow dynamics of the azygos vein on computed tomography can be an indication of superior vena cava obstruction. Recognition and accurate characterization of abnormalities of the azygos vein on imaging studies is critical to facilitate prompt diagnosis and direct workup when necessary. The main purpose of this article is to illustrate and describe the radiologic features of various congenital and acquired abnormalities affecting the azygos venous system.

A rare variation of the hemiazygos vein draining into the persistent left superior vena cava

During an educational dissection of a 72-year-old Chinese male cadaver, the hemiazygos vein (HAV) coursing the left side that drains into the persistent left superior vena cava was observed. The HAV was formed at the junction of the 9th to 11th right posterior intercostal veins, right subcostal vein, 5th to 11th left posterior intercostal veins, and left subcostal vein; it then ascended posteriorly to the thoracic aorta. After collecting the accessory hemiazygos vein, it crossed over the aorta and the pedicle of the left lung via the hemiazygos arch, then converged with a communicative branch (vein of Marshall) that emerged from the left brachiocephalic vein to form the persistent left superior vena cava and entered the pericardium at the level of the sixth thoracic vertebra. Upon opening the pericardium of our cadaver, the persistent left superior vena cava was found to drain directly into the significantly dilated coronary sinus at the level of the eighth thoracic vertebra. The azygos vein was formed by the union of the first to eighth right posterior intercostal veins and appeared to be finer and shorter than the HAV. The persistent left superior vena cava might be the result of incomplete degeneration of the left posterior cardinal vein. Knowledge of such variations could be of great value to surgeons placing peripherally inserted central catheters because incorrect placement of the azygos venous system can be detrimental to the patient. In addition, during heart surgery, awareness of such variations may prevent major complications, such as hemorrhage or damage to vascular structures, and possibly also provide new insights and perspectives to cardiovascular surgeries.

Unusual collateral vessel from right subclavian vein to left atrium, a rare complication of superior vena cava obstruction

The most commonly reported collateral systems in the setting of superior vena cava obstruction are azygos venous system, vertebral venous system, external and internal thoracic venous system based on McLntire and Sykes classification. A 49-year-old female with renal disease complained dyspnea on exertion. Transesophageal echocardiography showed significant mitral annular calcification, large multi-lobulated mass at posterior aspect of RA, and complete obstruction of superior vena cava by thrombus formation. Computed tomography angiography showed a collateral vein to the left atrium (LA) roof. This case report is the first one which shows development of collateral vein from right subclavian to LA.

Prominent Accessory Hemiazygos Vein representing Persistence of Cranial Portion of Posterior Cardinal Vein: Embryological Variant

ABSTRACT Introduction The azygos venous system has developed from the postcardinal veins of the embryo, and small parts persist only at the commencement of the azygos vein. Complex embryological development of these veins is a major cause for many possible variations of the azygos system. Materials and methods The present study was done in the Department of Anatomy, Government Medical College, Amritsar, on a male cadaver aged about 50 years. The thoracic cavity was opened to dissect the azygos system of veins. Results The system showed the persistent cranial part of the posterior cardinal vein. This led to the formation of a well-developed venous channel on the left side of the aortic arch and the thoracic aorta. This channel drained the 2nd to 10th left posterior intercostal veins and drained itself into the left brachiocephalic vein (LBV) after crossing the arch of aorta vertically on its right. There was no transvertebral communication between this channel and azygos vein on the right side. The hemiazygos vein (HAV) on the left side was normally formed and immediately drained into the azygos vein by turning to the left. The azygos vein on the right side was also normal. Conclusion The presence of such persistent embryological remnant, its position, and approximation to the structures near the arch of aorta should be taken into account to avoid radiological misdiagnosis and surgical complications. How to cite this article Sehmi S. Prominent Accessory Hemiazygos Vein representing Persistence of Cranial Portion of Posterior Cardinal Vein: Embryological Variant. Curr Trends Diagn Treat 2017;1(1):40-41.

Anatomical Variations of the Azygos Venous System: Classification and Clinical Relevance

Anatomical Variations of the Azygos Venous System: Classification and Clinical Relevance

Prenatal diagnosis of a variant of the azygos venous system.

BackgroundThe azygos venous system consists of the azygos vein on the right side and the hemiazygos and accessory hemiazygos on the left side. The azygos vein runs through the abdominal cavity along the right side of the vertebral bodies, in a cranial direction, passes through the diaphragm and reaches the mediastinum, where it forms the arch of the azygos which flows into the superior vena cava. Along its course, the azygos vein communicates with the intercostal veins on the right, the hemiazygos vein that collects blood from the left lower intercostal veins, and accessory hemiazygos vein that drains into the left upper intercostal veins. The last two, at the level of the seventh thoracic vertebra, unite and end in the azygos vein. The accessory hemiazygos vein is normally included in the length between T4 and T8. The embryological origin of the accessory hemiazygos vein is the result of an expansion in the direction of the cranial hemiazygos vein, which comes from the left upper sovracardinale vein (Dudiak et al. in Semin Roentgenol 24(1):47–55, 1989; Radiographics 11(2):233–246, 1991; Webb et al. in Am J Roentgenol 139(1):157–161, 1982).FindingsThis case report describes a rare variant of azygos vein system identified in prenatal diagnosis and confirmed by postnatal ultrasonography.ConclusionsThe observation of the patient has excluded hemodynamic alterations associated with vascular anomaly.

Injury to Azygos Venous System: A Co-Existing Injury in High-Impact Lethal Trauma.

About 50 cases of azygos venous system injuries following civilian trauma have been published in current literature. The purpose of our study was to investigate the incidence of these injuries, the causative mechanism and type of trauma, the co-existing injuries, and the mortality rate in our institution. We performed a retrospective review of all trauma patients who were admitted to the surgical department of the General Hospital of Rethymno during an 11-year period. Our study included patients arriving at our institution dead or alive with an azygos venous system injury following blunt or penetrating civilian trauma. Seven patients-five men and two women-were identified with azygos venous system injuries. Five had an azygos vein laceration, one suffered from both azygos and hemiazygos vein lacerations, and the last one had sustained hemiazygos and accessory hemiazygos vein injuries. All of them suffered from a blunt trauma. Three arrived at our hospital in extremis, and all died within 24h despite our resuscitation attempts. All of our patients were polytrauma patients. All of them had co-existing torso injuries which were severe in all but one case, three of them suffered also from serious head injuries, and all but one had at least serious extremity's injuries. Azygos venous system injuries are rare, although it seems that they are more frequent than current literature would indicate. Blunt trauma mechanism seems to be predominant in civilian trauma setting, and the patients have usually sustained a lot of serious and severe co-existing injuries with high resultant lethality.

Infrahepatic inferior caval and azygos vein formation in mammals with different degrees of mesonephric development.

Controversies regarding the development of the mammalian infrahepatic inferior caval and azygos veins arise from using topography rather than developmental origin as criteria to define venous systems and centre on veins that surround the mesonephros. We compared caudal-vein development in man with that in rodents and pigs (rudimentary and extensive mesonephric development, respectively), and used Amira 3D reconstruction and Cinema 4D-remodelling software for visualisation. The caudal cardinal veins (CCVs) were the only contributors to the inferior caval (IVC) and azygos veins. Development was comparable if temporary vessels that drain the large porcine mesonephros were taken into account. The topography of the CCVs changed concomitant with expansion of adjacent organs (lungs, meso- and metanephroi). The iliac veins arose by gradual extension of the CCVs into the caudal body region. Irrespective of the degree of mesonephric development, the infrarenal part of the IVC developed from the right CCV and the renal part from vascular sprouts of the CCVs in the mesonephros that formed 'subcardinal' veins. The azygos venous system developed from the cranial remnants of the CCVs. Temporary venous collaterals in and around the thoracic sympathetic trunk were interpreted as 'footprints' of the dorsolateral-to-ventromedial change in the local course of the intersegmental and caudal cardinal veins relative to the sympathetic trunk. Interspecies differences in timing of the same events in IVC and azygos-vein development appear to allow for proper joining of conduits for caudal venous return, whereas local changes in topography appear to accommodate efficient venous perfusion. These findings demonstrate that new systems, such as the 'supracardinal' veins, are not necessary to account for changes in the course of the main venous conduits of the embryo.

Rapports vasculaires thoraciques du nerf grand splanchnique droit

The surgical assumption of responsibility of the pancreatic pain requires either a truncular coelioscopic or radicular neurectomy of greater splanchnic nerves (gsn). The goal of our work is to describe the way and relations of the right gsn which are variable and rarely described. This constitutes an undeniable peroperational hemorrhagic risk during splanchnicectomy. After a double side thoracotomy and a bilateral sterno-clavicular desarticulation on 15 adult cadaveric subjects preserved by method of Winckler we removed the sterno-costal drill plate as well as the ventral rib arch and proceeded to a mediastinal evisceration of the thorax. Then we respected only the thoracic aorta and the oesophagus, the azygos venous system, the thoracic duct and the thoracic sympathetic chain. In some of the subjects, the azygos vein was injected (after catheterization of its stick) using gelatine coloured with blue paint. We studied the way and vascular relations of the right gsn. We measured the transverse distances between the origin of the gsn on one hand and the longitudinal axes of the azygos vein and the thoracic duct on the other hand. The relations of the right gsn trunk during its way related to the azygos vein in particular its constitutive origin and its affluents: ascending lumbar vein and twelfth intercostal vein. Sometimes the thoracic duct even a lymphatic node was near the gsn in the posterior infra-mediastinal space. A classification of the way and vascular relations of the right gsn in the thorax identified 3 anatomical types. The average distances separating the right gsn on one hand from the azygos vein and the thoracic duct on the other hand were respectively 5.7 mm and 11.2 mm. The vascular relations of the right gsn are very variable from one subject to another but primarily venous, sometimes lymphatic. They concerned the great thoracic vessels whose respect is essential in particular at the time of mini-invasive access procedure for a cœlioscopic splanchnicectomy.