[Spiral CT study of superior vena cava syndrome: correlation between collateral pathways and obstruction site and degree].

Background: To study the collateral pathways of superior vena cava syndrome ( SVCS) .

Methods: Thirty-one spiral CT phlebograms of patients with SVCS were obtained. Superior vena cava was divided into upper and lower segment by azygos arch, and the collateral pathways were divided into anterior and posterior groups according to their sites in the chest wall. The distribution of collateral pathways and obstruction site and degree of SVC were observed and analysed statistically . The drainage of SVCS was determined.

Results: Anterior group of collateral pathways, vertebral venous plexus and posterior intercostal veins were related to obstruction of upper segment of SVC ( P < 0. 05) . Obstruction of the lower part of SVC has relation to the hemiazygos vein ( P < 0. 05) . The correlation between obstructive degree and distribution of collateral pathways was not distinct in this study ( P > 0. 05) . When obstruction of upper segment of SVC occurred, blood could return to heart through azygos vein or anterior group vessels. While lower segment of SVC was occluded, blood could reflux through azygos vein and hemiazygos vein to right atrium.

Conclusions: Distribution of collateral pathways in SVCS is closely related to the obstruction site of SVC, but not to the degree of obstruction.