Venography in superior vena caval obstruction.

Abstract

VENOGRAPHY provides radiographic visualization of the superior vena caval system and offers a reliable means of obtaining precise information regarding the anatomical site and degree of obstruction in lesions of these veins. The procedure also demonstrates the pattern and extent of the collateral channel formation around sites of obstruction in the superior vena cava. McCord, Edlin, and Block (14) have observed that in the last two decades, following the introduction of contrast studies of blood vessels and use of venous pressure technics, there has been progressive development in our knowledge of lesions of the superior vena caval system. Hinshaw and Rutledge (10) have stressed the desirability of localizing the site of obstruction accurately if surgical treatment is contemplated. Anatomical Features The superior vena cava returns the blood from the head, neck, upper extremities, thoracic wall, and part of the upper abdominal wall. This great vein, measuring approximately 70 mrn. in length, is formed by the union of the two innominate veins. It is enclosed within the fibrous layer of the pericardium in the lower half of its extent and terminates in the upper and posterior part of the right atrium. Near the upper end, the azygos vein contributes blood from the thoracic wall. This latter vein is the one large tributary received by the superior vena cava. The azygos vein is not actually an unpaired vein, since there is a corresponding structure on the left side, the hemiazygos vein, which is smaller than the azygos and empties blood either partly or completely into it. McIntire and Sykes (15) emphasize the anatomical significance of the two very important chains of lymph nodes that encircle the superior vena cava. These groups of nodes, the right anterior mediastinal and the right laterotracheal chains, as well as the right bronchial nodes and some of the nodes of the tracheal bifurcation, are in close association with the vessel. Most of the structures of the right thoracic cavity, the mediastinum, and part of the structures of the left thoracic cavity drain into the lymph nodes closely related to the superior vena cava. Inflammatory or neoplastic disease in this part of the mediastinum or thorax offers a constant threat to these lymphatic chains, with possible obstruction of the superior vena cava from actual invasion or extrinsic pressure. The anterior and posterior boundaries of the superior mediastinum, through which the superior vena cava passes, are rigid parts of the thoracic wall. The lateral boundaries are rather elastic, being formed by the pliable pleural layers. These factors permit space-occupying lesions to expand laterally. Hinshaw and Rutledge have emphasized that the great veins are thin-walled, and that the blood flowing through them is under low pressure.