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The study presented an extremely rare case of real complete bilateral duplication of inferior vena cava (IVC) in a male cadaver which has never been reported before. Both IVC had approximately the same diameter. The right IVC drained into the right atrium; the left IVC continued as hemiazygos vein and drained into the superior vena cava. Three anastomotic venous channels, a cranial preaortic, a middle and a caudal retroaortic, joined both vessels. Multiple variations in the way of drainage of posterior intercostal veins, on both sides, were also present. The present report invalidates an old classification defining the two vessels when joined at the level of the renal veins as complete bilateral duplication of IVC. Although the presence of combination of venous variations is extremely rare, awareness of such variations is essential for clinical and surgical procedures to avoid misdiagnosis and surgical complications.

Azygos system of veins is the main source of venous drainage from the thoracic wall. Knowledge of azygos vein anomalies could be of importance to cardiothoracic surgeons and radiologists. We report a rare variation of azygos vein as seen in an adult male cadaver aged 65 years approximately. The azygos vein was formed by the union of left ascending lumbar and subcostal veins. It coursed upwards on the left side of descending thoracic aorta and crossed the left subclavian artery and the left vagus to terminate into the left brachiocephalic vein. It received left superior intercostal vein and left fifth to eleventh posterior intercostal veins. The hemiazygos and accessory hemiazygos veins were situated on the right side of the vertebral column. They received the right posterior intercostal veins and terminated into the azygos vein at the level of eighth thoracic vertebra.

Background: Thoracic paravertebral block (TPVB) is considered the gold standard for hemithoracic regional anaesthesia. Erector spinae plane block (ESPB) is a new posterior thoracic wall block. Multiple-injection costotransverse block (MICB) mimics TPVB but with injection points within the thoracic intertransverse tissue complex and posterior to the superior costotransverse ligament. We aimed to compare the spread of injectate into the thoracic paravertebral space (TPVS) resulting from single-injection ESPB and MICB, respectively, with TPVB. Methods: Ten soft-embalmed cadavers were utilised. In five cadavers, the right hemithorax was randomly allocated either to ultrasound-guided single-injection ESPB or single-injection TPVB; vice versa on the other side. In another five cadavers, the right hemithorax was randomly allocated either to ultrasound-guided MICB or multiple-injection TPVB. About 20 mL of dye was injected in each hemithorax with all techniques. Results: With TPVB, the dye was consistently present in the TPVS with concomitant epidural spread in the majority of cases. The injectate spread into the TPVS with ESPB (60%) and MICB (100%). MICB consistently stained the ventral rami (T1-7), communicating rami and thoracic sympathetic trunk without epidural spread. Dissection after MICB revealed dye spread into the TPVS via the costotransverse foramina and along the dorsal branches of the posterior intercostal veins. Conclusions: Consistent spread of dye into the TPVS colouring the ventral rami, the communicating rami, and the sympathetic trunk was observed with MICB; in this respect equivalent to TPVB. ESPB exhibited only partial success and was not equivalent to TPVB. No epidural spread was found with neither MICB nor ESPB.

Knowledge of variations of azygos and hemiazygos veins is of importance to cardiothoracic surgeons and radiologists during various surgical, radiological, and echography techniques. We report some unique variations of azygos system of veins observed during dissection classes for undergraduate medical students. The azygos vein was formed as usual by the union of right subcostal and ascending lumbar veins. The vein ascended upward and to the left to reach the midline at the level of the 9th thoracic vertebra. After ascending till 5th thoracic vertebra, it gradually inclined to the right of midline and terminated by opening into the superior vena cava at the level of the 3rd thoracic vertebra. There was no major variation in the tributaries of the azygos vein on the right side, except that the right superior intercostal vein crossed behind the azygos vein from right to left and opened into the left side of the azygos vein. Further, two anastomotic veins connected the 10th, 11th and 12th posterior intercostal veins with each other to form two anastomotic circles on the right side of 10th to 12th thoracic vertebrae. The hemiazygos vein bifurcated on the left side of the 10th thoracic vertebra and the two ends opened into the azygos vein at the level of 9th and 10th thoracic vertebrae forming a venous circle in front of the 10th thoracic vertebra. The course of accessory hemiazygos vein was noteworthy. Instead of its classic descending course, the vein ascended upward from the left side of the 8th thoracic vertebra till the 6th thoracic vertebra before opening into the azygos vein.

The internal vertebral venous plexus (IVVP) plays a putative role in thermoregulation of the spinal cord. Cold cutaneous venous blood may cool, while warm venous blood from muscles and brown fat areas may warm the spinal cord. The regulating mechanisms for both cooling and warming are still unknown. Warm venous blood mainly enters the IVVP via the intervertebral veins. In the thoracic area these veins are connected to the posterior intercostal veins. In this study, anatomical structures were investigated that might support the mechanisms by which warmed venous blood from the intercostal muscles and the recently described paravertebral patches of brown adipose tissue are able to drain into the vertebral venous plexus. Therefore, tissue samples from human cadavers (n = 21) containing the posterior intercostal vein and its connections to the IVVP and the azygos veins were removed and processed for histology. Serial sections revealed that the proximal parts of the posterior intercostal veins contained abundant smooth muscle fibers at their opening into the azygos vein. Furthermore, the walls of the proximal parts of the posterior intercostal veins contain plicae that allow the vessel to dilate, thereby allowing it to serve as a pressure chamber. It is suggested that a cold induced closure of the intercostal/azygos opening can result in retrograde blood flow from the proximal posterior intercostal vein towards the IVVP. This blood flow would be composed of warm blood from the paravertebral brown adipose tissue and blood containing metabolic heat from the muscles draining into the intercostal veins.

La estructura de las venas de la cavidad torácica varía significativamente en función de sus conexiones. Treinta cadáveres embalsamados con la técnica de Thiel fueron disecados (18 mujeres, 12 hombres), con edades comprendidas entre 48 y 98 años (media 81.3±12.40). Los pulmones, el corazón, la aorta torácica, el esófago y la pleura parietal fueron cuidadosamente retirados para permitir la visualización de las venas ácigos, hemiácigos y hemiácigos accesoria así como el conducto torácico. En la mayoría de los especímenes (21) se encontró que las venas intervertebrales estaban directamente conectadas con el sistema venoso ácigos en vez de con la parte terminal proximal de las venas intercostales posteriores. Se observó también que dicha distribución es más común en el lado derecho, pero no en todos los niveles vertebrales. Estas conexiones podrían jugar un rol en la regulación del volúmen de sangre entre los sistemas venosos ácigos y vertebral: también podrían actuar como vías metastásicas entre las regiones torácica y abdominal. Dado que su aspecto es bastante similar al de los vasos intercostales posteriores, es importante que los cirujanos sean conscientes de esta variación para evitar lesiones que induzcan hematomas postoperatorios. Veins in the thoracic cavity are highly variable in terms of their communications. Thirty Thiel-embalmed cadavers were dissected (18 females and 12 males), ranging in age from 48 to 98 years old (mean 81.3±12.40). The lungs, heart, thoracic aorta, oesophagus and parietal pleura were removed carefully to expose the azygos, hemiazygos, accessory hemiazygos veins and thoracic duct. In most specimens (21) intervertebral veins were connected directly to the azygos venous systems rather than the proximal end of the posterior intercostal veins. This presentation was observed to be more common on the right side, but not at all vertebral levels. These communications could play a role in regulating blood volume between the azygos and vertebral venous systems; they may also act as metastatic pathways between the thoracic and abdominal regions. As they mimic posterior intercostal vessels, it is important for surgeons to be aware of this variation to avoid injuries leading to postoperative hematomas.

We noted a large amount of intravenous gas during balloon kyphoplasty on CT imaging. Formal assessment to understand the extent, possible causes and implications was undertaken. Ten consecutive cases of balloon kyphoplasty were performed under general anaesthesia in the prone position, on a single vertebral level using a two-step technique under combined fluoroscopic and CT guidance. CT of the affected vertebra was performed before, after, and intermittently during the procedure. In 2 cases delayed CT was carried out in the supine position. Gas was seen on CT imaging, but not on conventional fluoroscopy. The gas is most likely to be air introduced during the procedure and was seen in the epidural and paravertebral venous plexus, posterior intercostal veins, renal veins, IVC and azygos vein. The average measured volume of gas seen on the post-procedure CT imaging was 1.07 mL, range 0.16–3.97 mL. There was no correlation of the measured amount of gas to the procedure duration or location, the use of a curette or the injected cement volume. Delayed CT in the supine position no longer showed air in the local venous system. Balloon kyphoplasty is associated with the fluoroscopically invisible introduction of air into the vertebral and paravertebral veins and deep systemic veins and is likely to be much more extensive than identified on CT imaging. There is potential for serious air embolism in kyphoplasty and if there is a sudden deterioration in patient condition during the procedure the possibility of this complication needs to be considered.

During the educational dissection of a 68-year-old Chinese male cadaver, an azygos vein (AV) coursing on the left side with double superior vena cava was observed. The left superior vena cava (LSVC) began from the confluence of the left internal jugular and left subclavian veins, and extended downwards medially into the left edge of the dilated coronary sinus. The right superior vena cava was formed by the union of the right internal jugular and right subclavian veins, and drained into the right atrium from the above. The AV was formed by the union of the right and left ascending lumbar veins at the level of the tenth thoracic vertebra. It ascended along the left margin of the thoracic vertebra, receiving almost the bilateral posterior intercostal veins and then extended into the LSVC on the left wall via the azygos arch. Better understanding of these variations will reduce unnecessary and potential harmful testing, and unneeded patient anxiety.

Multiple variations of the azygos venous system were detected during routine dissection. The hemiazygos vein was underdeveloped. On the left side of the thorax, posterior intercostal veins between the 8th and 11th intercostal spaces and the subcostal vein drained into the azygos vein independently. In addition, the posterior 4th, 5th, 6th and 7th intercostal veins united and formed two superior and inferior trunks. The superior common trunk, at the level of the T4 vertebra, crossed the vertebral column obliquely, lying anterior to the aorta and posterior to the esophagus, opening into the azygos vein at the level of the T4 vertebra. The other structures in this part were normal. There were different courses of the azygos vein system. This variation is important in mediastinal surgery and also in the interpretation of radiographs.

Introduction The posterior thoracic wall, an area drained by the azygos venous system, is a common site for surgical intervention. Since the venous part of the cardiovascular system is subject to most common variation, abnormalities in the azygos venous system are often reported. Case presentation During routine dissection classes for undergraduate medical students, we encountered a variation in the azygos venous system in a 65 years old south Indian male cadaver. We observed that there was no accessory azygos vein, and left 4th, 5th, 6th and 7th posterior intercostal veins terminated directly into azygos vein. Conclusion Identifying these types of variations is important during imaging this region and surgical operations of mediastinum.