AN INVESTIGATION OF RADIAL REFLUX IN AN ISOLATED PERIPHERAL CANINE VEIN SEGMENT

Objective: To investigate the effects of flow from the vein lumen into the vasa venarum (radial reflux) and the factors regulating it. Design: In vivo and in vitro animal study. Setting: University Department of Physiology. Materials: Segments of canine vein were perfused in vitro (n = 84) and in situ (n = 60). Main outcome measures: Specimens were studied by conventional histology using light microscopy. Results: Radial reflux caused dilatation of constricted segments and when associated with turbulent flow resulted in the formation of acute short-lived varices, marked dilatation of sinusoidal venules at the medio-adventitial junction of the segments and of sinusoidal venules in the paradventitial tissue. Conclusion: During laminar flow radial reflux operated as a feedback to regulate venoconstrictor tone. During turbulent flow it caused more widespread vascular changes and inhibited adrenergic activity. The changes are of particular interest because they mimicked those that characterize the early stage of varicose veins.