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CT of the normal azygos venous system. Contrast-enhanced CT axial images show the normal appearance of the azygos vein arching from the right paraspinal space to the superior vena cava (a). The azygos vein runs longitudinally on the right side of the thoracic vertebral bodies (a). The hemiazygos vein runs on the left side of the spine (b) until anastomosis with the azygos vein on T8-9 as shown in the sagittal and coronal view (c–d)
Source publication
The azygos venous system represents an accessory venous pathway supplying an important collateral circulation between the superior and inferior vena cava. The aim of this article is to revise the wide spectrum of changes ranging from normal to pathological conditions involving the azygos system.
Teaching points
• The azygos vein is a collateral v...
Similar publications
We report an interesting case of a man with a persistent left superior vena cava (PLSVC) with left azygos vein who underwent electrophysiological evaluation. Further evaluation revealed congenital dilated azygos vein, while a segment connecting the inferior vena cava (IVC) to the hepatic vein and right atrium was missing. The azygos vein drained in...
The aim of this study was to assess the computed tomography angiography (CTA) manifestations of collateral circulations in patients with Budd-Chiari syndrome (BCS). Eighty patients with BCS were examined by CT scan. Using the CTA images of the relevant blood vessels, including the affected hepatic veins (HVs) and inferior venae cavae (IVCs), the co...
Key Clinical Message
Isolated persistent left superior vena cava (SVC) in the absence of right SVC is a rare congenital variant of thoracic venous drainage with the left subclavian and jugular veins that drain into the right atrium through the coronary sinus. Inferior vena cava interruption with azygos continuation is another congenital anomaly res...
Interrupted IVC (also known as Azygos continuation of the inferior vena cava) is a relatively uncommon congenital condition with prevalence 1.5% (0.2-3%) of the general population (Bass et al.). Although it's usually asymptomatic condition, splenic or cardiac abnormalities could be associated (Hardwick et al.). Incidental diagnosis during prenatal...
Citations
... Pathophysiologically, an obstruction after the influxof the azygos vein into the SVC results in a stream inversion, and blood may flow in a retrograde manner via this pathway and return to the RA via the IVC. 18,19 Patients' Consent Written informed consent was obtained from the patients for the publication of these case reports and any accompanying images. Copies of the written consent forms are available for review. ...
We report two cases of rare invasive tumors presenting with transvenous and intracardiac extensions. In one instance, an unusual invasive thymoma type A penetrated into the heart chamber; the other case was an extension of a myxoma into the right atrium that was associated with superior vena cava syndrome. Our interest was stimulated by the rarity of these clinicopathological observations and the unusual clinical features of diagnostic and therapeutic methods presented by these cases.
... The pathway consists of the azygos, hemi-azygos, and accessory hemi-azygos veins. All of them develop from the last portion of the posterior cardinal veins [ 3,4 ]. ...
Esophageal cancer (EC) is among the top ten worldwide causes of cancer related morbidity and mortality. Squamous cell carcinoma (SCC) accounts for over 90% of all cases in sub-Saharan Africa [1]. Azygos arch and azygos vein tumor thrombus in esophageal squamous cell carcinoma (ESCC) is a rarely reported phenomenon. We report a case of tumor thrombus in the azygos vein and arch in a patient with esophageal squamous cell carcinoma. To date only a single case of such tumor thrombus in the arch of the azygos vein have been reported which was subsequently managed with neoadjuvant chemotherapy followed by radical resection [2].
... Thus, there seems to be a discrepancy between our results and the clinical human application which may partly be explained by the differences in collateral supply between experimental animals and humans, e.g., the presence of an azygos vein [4,5,[29][30][31]. The azygos vein provides an important venous collateral pathway between the IVC and the superior vena cava (SVC) in humans [32,33]. ...
... There are other venous collaterals between the lower and upper body, including the hemiazygos vein, the paired inferior epigastric-, superior epigastric-, and internal thoracic veins emptying into the brachiocephalic veins, and the lateral thoracic veins emptying into the axillary veins [24,[32][33][34]. In addition to the azygos vein, these collaterals may counteract some of the venous lower body congestion when applying REBOVC in humans (Fig. 4). ...
... In humans, the azygos vein, via the left gastric and the esophageal veins, is an alternative pathway to shunt splanchnic blood to the systemic circulation when the portal vein or hepatic circulation are blocked (Fig. 4) [32][33][34][35]. Pigs lack an azygos vein and therefore an efficient portosystemic collateral circulation, providing an anatomical basis for an extensive splanchnic venous congestion in portal occlusion [36,37]. ...
Purpose
Combining resuscitative endovascular balloon occlusion of the aorta (REBOA) and the inferior vena cava (REBOVC) with open surgery is a new hybrid approach for treating retrohepatic vena caval injuries. We compared endovascular total hepatic isolation with supraceliac REBOA ± suprahepatic REBOVC and no occlusion in experimental retrohepatic vena cava bleeding regarding survival, bleeding volume, hemodynamic stability, and arterial collateral blood flow.
Methods
Twenty-five anesthetized pigs (n = 6–7/group) were randomized to REBOA; REBOA + REBOVC; REBOA + infra and suprahepatic REBOVC + portal vein occlusion (endovascular Heaney maneuver, four-balloon-occlusion, 4BO) or no occlusion. After balloon inflation, free bleeding was initiated from an open sheath in the retrohepatic vena cava. Bleeding volume, right internal thoracic artery (RITA) blood flow, hemodynamics, and arterial blood variables were measured until death or up to 90 min.
Results
The REBOA group had a longer median survival time (63 min) compared with the 4BO (24 min, P = 0.02) and no occlusion (30 min, P = 0.02) groups, not versus the REBOA + REBOVC group (49 min, P > 0.05). The first 15 min accumulated bleeding was comparable in all groups (P > 0.05); Thereafter, bleeding volume was higher in the REBOA group versus the 4BO group (P < 0.05), not versus the other groups. RITA blood flow and MAP were higher in the REBOA group versus the other groups after 10 min of bleeding (P < 0.05).
Conclusions
Endovascular Heaney maneuver was not beneficial for survival or hemodynamic stability in this porcine model, whereas supraceliac REBOA was. Anatomical differences in thoracoabdominal collaterals between pigs and humans must be considered when interpreting these results.
... Unless the obstruction involves the azygos vein insertion site of the SVC, the azygos-hemiazygos pathway predominates with or without other collaterals. Based on obstruction site level and dominant collateral pathway, the azygos vein can flow in the anterograde or retrograde direction (5,27). ...
... (5). Conversely, the hemiazygos vein ascends along the vertebral column on the opposite side of the azygos vein, corresponding to the lower part of the azygos vein. ...
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.
... The widespread variation in the AVS is often explained by processes occurring during embryological development. Nevertheless, while multiple studies in current literature argue that most AVS variants result from congenital causes, few describe variations in the AVS that are acquired as part of pathological processes [16]. In this section, we explore both congenital and acquired variants while discussing the atypical variations found in this study. ...
... During weeks 5 to 7 of embryogenesis, transverse anastomotic channels divert venous blood from the left to the right side, after which the veins on the left side shrink in size [17]. Hence, a principal AZY on the right side is found most of the time paired with a structure at least alluding to a HAZY and AHAZY on the left [16]. Most variations are observed on the left side, including aplasia of the HAZY and AHAZY or poorly defined left-sided structures [18]. ...
... Others are due to tumors or other processes that cause compression or intraluminal filling defects [16]. An example of a fluid overload case was described in Case 3 above, where a COPD patient presented with an abnormal dilation of the blood vessels in the AVS, possibly from venous stasis [19]. ...
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.
... Collateral pathways play a crucial role in maintaining proper drainage from the legs and pelvis through the deep, median, portal, and superficial pathways. [4][5][6] Malformations of the IVC include IVCA, a left IVC, double IVC, azygos continuation of the IVC, a circumaortic left renal vein, a retroaortic left renal vein, a double IVC with a retroaortic right renal vein and hemiazygos continuation, a double IVC with retroaortic left renal vein and azygos continuation, a circumcaval ureter, and isolated accessory hemiazygos vein. 5,7 IVCA has a prevalence of 0.0005% to 1% 6 and occurs due to underdevelopment of the posterior and supracardinal veins. ...
Chronic venous insufficiency, caused by inferior vena cava occlusion, can lead to thromboembolic complications and tissue loss. We present two cases of azygos vein stenting (AVS) in which vena cava recanalization techniques were exhausted. In the first case, the left iliac vein and vena cava were recanalized and stented; however, the right iliac vein had been previously resected and required AVS. Conventional recanalization attempts from the right and left iliac systems failed in the second patient with congenital inferior vena cava occlusion; therefore, AVS was chosen to establish in-line drainage
... 23.074 eISSN 2093-3673 cerebral venous system therefore forming potential metastatic pathway to brain in cases of breast and bronchial carcinoma. It also forms a significant communicating channel between superior and inferior vena cava, thus serving as an alternate route for venous return from the lower parts of the body if primary venous channel is obstructed [8][9][10]. ...
... The AV diameter significantly correlate with the intravascular fluid circulation. Furthermore, increased capillary blood volume (CBV) following over-infusion as in cases of renal failure, with accompanying fluid overload , results in an associated increase in the width of the AV [10]. Therefore, increase in 5 mm of the vascular pedicle relates to 1 L increase in circulating fluid [32,33]. ...
... Although, the width of the AV does not correlate substantially with the CBV, but it does with the right mean atrial pressure [10]. These relationships have been observed in patients with any degree of severity of cardiac failure and CBV values ranging from normal to very high [32,33]. ...
The azygos vein can be formed as a single root, two roots, and three roots, namely lateral, intermediate and the medial roots respectively. The hemiazygos vein and the accessory hemiazygos vein are the tributaries of azygos vein rather than its left side equivalents. Its variations, especially in young persons without any relevant risk factors, may result in thromboembolic illness. This study aimed to describe the morphological and morphometric variations of azygos system of veins. The present study was conducted on thirty formalin fixed adult human cadavers by dissecting azygos vein from formation to termination and variations were noted. The azygos vein was formed by a single root in 56.7%, by two roots: the lateral root and intermediate root in 36.7% cases and by the lateral root and medial root in 6.6%. The vertebral level of termination of azygos vein was seen at the level of T4 vertebrae in 70% cases, at the level of T3 vertebrae in 20% of cases and at the level of T5 vertebrae in 10% cases. The course of azygos vein was varying in 13.3%. These morphological variations can be useful while performing mediastinal surgery, mediastinoscopy, surgery of the deformations of the vertebral column, neurovascular surgeries of the retroperitoneal organs, disc herniation and fracture of thoracic vertebrae.
... Absent azygos vein is a rare anomaly of the venous system in consequence to failure of development of the superior segment of the right supra-cardinal vein [1]. This anomaly is usually incidentally discovered [2], with only 16 publications reporting it. Due to the paucity of cases, it is rarely reported with oesophageal atresia ± tracheoesophageal fistula (OA ± TOF). ...
... In the previously published cases, most of the cases were discovered incidentally while performing a chest radiological study and were confirmed by computed tomography (CT), some cases were detected unexpectedly during a thoracic intervention [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] (Table 1). It can be suggested by chest x-ray when the density of azygos vein is absent and a secondary aortic nipple, adjacent to arch of aorta, is prominent due to the engorged hemiazygos vein and left superior intercostal vein [2,4]. By retrograde review of our case's chest x-ray, we managed to identify similar findings suggestive of absent azygos vein as well as possible prominent left-sided superior vena cava (Fig. 3), however CT will be needed to verify these radiological findings. ...
... Although the absence of azygos vein did not cause any vascular compromise in our case, the vein assessment is crucial for other patients with major cardiac anomalies with abnormal venous drainage, to act as an auxiliary venous pathway, to overcome any obstruction of the major veins [2,12]. ...
Absent azygos vein is a rare anomaly of the venous system, which is commonly an incidental finding, with only few publications reporting it. Due to the scarcity of cases, it is rarely reported with oesophageal atresia ± tracheoesophageal fistula (OA ± TOF), which is usually accompanied with cardiac anomalies in up to 80% of the cases. This association has only been reported thrice in literature. We report a 6-day-old female who was referred to our centre after diagnosis of OA + TOF. The patient had no associated anomalies apart from small patent foramen ovale and small ventricular septal defect; however, there was no functional compromise. Upon thoracoscopic exploration, azygos vein could not be visualised. Thoracoscopic repair was performed, and the postoperative period was uneventful. On follow-up, the patient had no postoperative complications. Absent azygos vein is a rare anomaly with few cases reported throughout the literature. Azygos vein is considered an important landmark intraoperatively because it guides the surgeon to the TOF site. Moreover, it might be important in other patients with major cardiac anomalies with abnormal venous drainage who might need further surgical correction.
... Typically the IVC is formed at the L5 level by the union of the right and left common iliac veins [11]. Besides the right adrenal gland, right gonad, and liver, four lumbar veins from the posterior abdominal wall also drain into the IVC [11]. ...
... Typically the IVC is formed at the L5 level by the union of the right and left common iliac veins [11]. Besides the right adrenal gland, right gonad, and liver, four lumbar veins from the posterior abdominal wall also drain into the IVC [11]. The paralumbar veins interconnect the lumbar and the ascending lumbar veins [11]. ...
... Besides the right adrenal gland, right gonad, and liver, four lumbar veins from the posterior abdominal wall also drain into the IVC [11]. The paralumbar veins interconnect the lumbar and the ascending lumbar veins [11]. The azygos venous system is on both sides of the vertebral column, consisting of the azygos vein and its tributaries, hemiazygos, and accessory hemiazygos vein [11]. ...
The absence of the inferior vena cava (IVC) is a rare abnormality reported in less than 1% of the population. The condition is usually the result of defects during embryogenesis. The collateral veins are enlarged with agenesis IVC, enabling blood transport to the superior vena cava. Although the alternate pathways enable venous drainage of the lower extremities, IVC agenesis (IVCA) may predispose to venous hypertension and complications, including thromboembolism. This report includes a case of a 35-year-old obese male who presented with deep vein thrombosis (DVT) in his left lower extremity (LLE) with no predisposing factors, which led to an incidental discovery of the inferior vena cava agenesis. Imaging showed thrombosis of the deep veins of the LLE, absence of the IVC, enlarged paralumbar veins, filling of the superior vena cava, and left renal atrophy.
The patient responded to therapeutic heparin infusion, and catheter placement and thrombectomy were performed. The patient was discharged on the third day with medications and vascular follow-up. It is essential to recognize the complications of IVCA and its correlation with other findings, such as atrophy of the kidney. The agenesis of IVC is a highly under-recognized cause of DVT of the lower extremities in the young population without other risk factors. Hence, a complete diagnostic evaluation is necessary for this age group, including imaging for vascular anomalies, besides the thrombophilic screening.
... 6 In some cases, it may drain into the right brachiocephalic or subclavian vein or into the intrapericardial part of superior vena cava of the right atrium. 7 Azygos vein may show normal physiological enlargement in supine position and in overhydration or mid-trimester of pregnancy or in pathological conditions like renal failure. [8][9][10] The hemiazygos vein usually originates from a common trunk formed by the union of the left ascending lumbar vein and the left subcostal vein. ...
