Collateral pathways in occlusion of the superior vena cava and its tributaries.

Abstract

Complete or partial occlusion of the superior vena cava and innominate veins is due to malignant tumors of the mediastinum in about 80 per cent of all cases (1, 3–5). Other causes reported are: benign tumors (5), tuberculosis (9), histoplasmosis (7), idiopathic fibrosis (2), syphilis (5), pyogenic infections (5), aneurysm of the ascending aorta (5), hematoma (5), and idiopathic thrombophlebitis (5). Clinical examination usually reveals unilateral or bilateral engorgement and tortuosity of the veins of the arms, neck, and thorax with or without soft-tissue edema. The areas of venous distension depend on the site of obstruction and the collateral pathways. At times, when there is no visible venous engorgement, edema may be the only clinical finding. Other observations are congestive changes in the eyes and nasal mucosa and facial cyanosis. Significant information about the site of obstruction and the collateral circulation is obtained by serial venography (8). Multiple occluded segments may be demonstrated. Recognition of thrombi extending from the occluded segment is important in the evaluation of therapy. The purpose of this paper is to discuss and illustrate the various collateral pathways noted on venography in occlusion of the superior vena cava and the innominate veins. Anatomy and Discussion The collateral venous pathways in obstruction of the superior vena cava or its major tributaries may be classified as follows: A. Collaterals bypassing the upper superior vena cava—anastomoses between innominate tributaries and azygos tributaries (Fig. 1, A and B). B. Collaterals between the superior vena caval system and the inferior vena caval system 1. Along the posterior trunk a. Azygos system (Fig. 1, A and B) b. Vertebral venous plexuses (Fig. 1, B and C) 2. Along the anterior trunk a. Internal thoracic, inferior epigastric anastomoses (Fig. 1, A) b. Lateral thoracic, superficial epigastric anastomoses (Fig. 1, A) C. Collaterals between the anterior and posterior aspects of the trunk 1. Anterior intercostal, posterior intercostal anastomoses (Fig. 1, A) 2. Lateral thoracic, internal thoracic anastomoses (Fig. 1, A) 3. Lateral thoracic, azygos system anastomoses (Fig. 1, A) D. Collaterals across the midline 1. Cervical venous network (Fig. 1, C) 2. Internal thoracic crossing veins 3. Azygos hemiazygos anastomoses (Fig. 1, A and B) 4. Vertebral venous plexuses (Fig. 1, B and C) E. Collaterals between the arm and thorax 1. Lateral thoracic, intercostal, internal thoracic anastomoses (Fig. 1, A) 2. Cephalic, jugular anastomoses over the shoulder and supraclavicular fossa (Fig. 1, A) Two major venous systems drain into the superior vena cava via the innominate veins.