Direction of Blood Flow in a Vein

Abstract

Determining the direction of blood flow in the veins of the anterior abdominal wall is important because it differentiates cirrhosis from vena caval obstruction. In patients with dilated abdominal wall veins due to cirrhosis, the direction of blood flow is away from the umbilicus (radiating like a star from the umbilicus), whereas in vena caval obstruction, the direction of blood flow is either completely above downward (superior venacaval obstruction) or completely below upward (inferior venacaval obstruction). The technique of determining the direction of blood flow in a vein is described in standard clinical manuals. In inferior vena caval obstruction, anterior abdominal veins are dilated. To determine the direction of blood flow in a vein, first, the vein that is free from branches for a distance of 3 cm is identified. Second, 2 fingers are pressed close together and placed over the middle of the venous segment. Third, both fingers are moved in the opposite direction, “milking” and emptying the underlying vein; this results in complete emptying of the vein. Finally, 1 of the fingers is released, and the speed of the filling of the vein in one direction can be observed, and then the procedure is repeated in the other direction. Filling from below upward is slightly faster than the speed of filling from above downward (online video supplement is linked to this article). In the early phases of venous distension, this difference in flow rate will be clear. However, the valves of the vein become incompetent when the distension is long-term, and then the differences in flow rate will be less distinct.