What is the role of maximum venous outflow (MVO) measurement in the diagnosis of varicose veins and spider veins (telangiectasia)?

Updated: Sep 25, 2020
  • Author: Robert Weiss, MD; Chief Editor: William D James, MD  more...
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The MVO measurement is used to detect obstruction to venous outflow from the lower leg, regardless of cause. It is a measure of the speed with which blood can flow out of a maximally congested lower leg when an occluding thigh tourniquet is suddenly removed.

The advantage of MVO testing is that it is a functional test rather than an anatomic one, and it is sensitive to significant intrinsic or extrinsic venous obstruction from any cause at almost any level. It can detect obstructing thrombus in the calf veins, the iliac veins, and the vena cava, where ultrasonography and venography are insensitive. It also detects venous obstruction due to extravascular hematomas, tumors, and other extrinsic disease processes.

The disadvantage of the test is that it is sensitive only for significant venous obstruction and does not detect partially obstructing thrombus. It is not useful for detection of venous insufficiency states. A normal MVO absolutely does not rule out deep vein thrombosis.

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