Abstract
When veins are obstructed, venous return is hindered and venous pressure increases.
The same end result is seen when the competency of venous valves is lost and blood
flows back into the segments from which it was just pumped despite a normally functioning venous pump. Obstruction most often occurs following an episode of deep
venous thrombosis (DVT) where the veins are occluded by the process and do
not, or only partially recanalize after the process subsides. However, other processes,
such as compression by lymph nodes or other masses, can also cause obstruction.