Use the retrograde filling (Trendelenburg) test to assess the valves of the communicating veins and the saphenous system.

■  With the patient supine, elevate one leg to about 90º to empty it of venous blood.

■  Occlude the great saphenous vein in the upper thigh by manual compression, using enough pressure to occlude this vein but not the deeper vessels.

■  Ask the patient to stand. While you keep the vein occluded,watch for venous filling in the leg. Normally, the saphenous vein fills from below, taking about 35 seconds as blood flows through the capillary bed into the venous system.

■  After the patient stands for 20 seconds, release the compression and look for sudden additional venous filling. Normally, slow filling continues because competent valves in the saphenous vein block retrograde flow.

When both steps of this test are normal, the response is termed“negative– negative.”

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