This is the term used to describe the temporary reversed direction of blood flow in the vein. Reflux results from the damaged one way valves in the lower extremity due to gravity. Enlargement and then kinking of the veins results from the damaged valves. This usually happens in the superficial veins which are not supported by muscle as in deep veins. Deep veins (between muscle layers) can also become enlarged either by bad valves or by blockage due to deep vein thrombosis (clotting).