ULTRASTRUCTURE OF EVOLVING DEEP VENOUS COLLATERALS

Objective: To explore the structure of obstructive venous collaterals. Design: A total of 25 rats underwent unilateral ligation of the dista l common femoral vein. Bilateral (control and test) vein segments with collaterals were harvested and studied with conventional light micros copy and electron microscopy at 2-week intervals for 10 weeks post-lig ation. Results: Obstructive collaterals were quite unlike normal contr ols throughout the study. Initially, post-obstructive collateral walls showed disorganization of collagen, elastin, smooth muscle cells, and adventitia, white endothelial cells became more rounded and compact. The dense protein subendothelial deposits noted early became organized and moved more deeply into the wall at subsequent study intervals. Mi nimal motivation of smooth muscle cells, coalescence of elastic lamina , condensation of collagen and some organization of the wall were note d. Conclusion: Inability of deep collaterals to function with normal w all properties is likely to be secondary to the disruption of connecti ve tissue and sustained disorganization of the vein wall noted through out the evolution of collateral formation.