The azygos vein and its pleural reflections. I. Normal roentgen anatomy

A semi-quantitative approach to variation of the azygos vein course

The azygos vein (AV) is typically described (illustrated) as ascending vertically on the right of thoracic vertebrae. Most thoracic vein studies have focused on tributary patterns, but some have noted more leftward AV courses. This study statistically documents variation in AV course independent of tributary patterns. A more statistical approach to the probable position of AV at different vertical levels may aid clinicians in locating and assessing it in clinical contexts. The AV course was exposed in 84 cadavers by removing overlying viscera between the aortic hiatus and tracheal bifurcation. Subjectively, non-pathological specimens were digitally photographed in anterior view. For each photo, a scaled grid was used to mark the horizontal position of the AV center at each of five vertical levels. The summated numerical distributions showed the following: ∼5% of the AVs ascended on the right side (classical) position, ∼30% did not cross the midline, ∼70% included part or all of their course left of the midline, and ∼14% reached the extreme left side. Based on this data, the modal AV course (1) begins at, or to the right of, the midline, (2) deviates leftward, (3) crosses the midline below mid-level, (4) reaches a leftward maximum at about 3/5 of its course, (5) then deviates rightward (often only reaching the midline at the uppermost level). In several noticeable cases, the leftward maximum was associated with large connections to left-side veins, suggesting a possible tension mechanism exerting traction on the AV over time.

Azygoesophageal recess

Knowledge of the normal radiologic appearance and manifestations of disease in the azygoesophageal recess can facilitate the detection and diagnosis of intrathoracic disease. The azygoesophageal recess is located lateral or posterior to the esophagus and anterior to the spine. It extends from the anterior turn of the azygous vein to the aortic hiatus. The configuration of the azygoesophageal recess is normally a smooth arc convex to the left. Because the right lung extends into the recess, pathology in this region can often be detected radiographically and typically manifests as increased opacity and/or as a contour abnormality. In adults, convexity directed to the right and immediately below the level of the azygous vein on a frontal radiograph is abnormal and requires further evaluation.

Migration of jugular or subclavian venous catheters into inferior tributaries of the brachiocephalic veins or into the azygos vein, with possible complications

Six children are reported in whom a central venous catheter from the internal jugular or the subclavian vein migrated to an anomalous position: the left superior intercostal vein in the first two cases, the thymic vein in the third, and the azygos vein in the last three. Resultant complications in five cases were: extravasation of the infusate in the first and third case; local vascular stenosis or complete vascular occlusion in the second and fifth case; and obstruction of the azygos arch due to local thrombosis and possible stenosis, with a likely extravasation of the infusate, in the sixth case. The mediastinal vascular anatomy related to these central venous catheters is reviewed with reference to similar and related cases in the literature.

Abnormalities of the azygo-oesophageal recess at computed tomography

The azygo-oesophageal recess is well demonstrated at CT. It may be distorted by pathologic processes in mediastinum, pleura and lung. Illustrations of the various conditions have been selected from 933 CT examinations.

Computed tomography of the azygo-oesophageal recess. Normal appearances

Computed tomography of the azygo--oesophageal recess was performed in 85 normal subjects. The recess was convex towards the left or had an approximately straight left wall. Convexity towards the right did not occur. Localized bulges caused by the azygos vein, oesophagus and aorta were frequent. The recess became gradually deeper caudally in patients below 50 years of age. Above that age a marked posterior extension of the heart and a prevertebral position of the aorta often caused a localized shallowing at the level of the inferior pulmonary veins or the ventricles.

Malignant versus benign paravertebral widening in children

Dorso-medial pleural reflection line anomalies occur in malignant tumours, neuroblastoma being the commonest one, in benign tumours, spinal inflammatory disorders and in cases of pseudotumours of different origin. The latter group comprises normal structure variants, malformations and acquired disease but also a small number of transitory or permanent lesions of uncertain or obscure origin. The radiological manifestations encountered are displacement, obliteration or blurring of the paraspinal contour, sometimes a frank paravertebral mass. Based on a case material consisting of 65 patients the importance of recognizing this feature is stressed. An approach to clinical and radiological diagnosis is discussed.