In a reflux study, which observation suggests venous reflux when there is calf compression followed by a color change on release?

In a reflux study, the observation of a transition to red color upon the release of calf compression indicates venous reflux. When compression is applied to the calf, blood is displaced from the veins, and the color of the skin may become less red due to reduced blood flow. Upon release of the compression, if there is a significant amount of venous reflux, the blood will rush back into the veins, leading to increased blood flow and oxygenated blood returning to the area. This influx is reflected in the skin color transitioning to red.

A persistent blue color would suggest a lack of adequate blood flow or venous stasis but does not provide confirmation of reflux in this context. If the color remains unchanged, this too would suggest stability in blood flow and no significant reflux issue. The appearance of yellow may indicate other vascular or pathological conditions unrelated to venous reflux specifically. Thus, a transition to red upon compression release is the definitive sign of venous reflux in this scenario.