 The purpose of this examination is focused mainly on the study of two pathologies ; venous thrombosis and venous insufficiency . It allows the examiner to evaluate the gross anatomy of the superficial and deep venous networks as well as the blood flow direction , which is crucial in determining vein pathology . It has become the reference standard used in the assessment of the condition and hemodynamics of the veins of the lower limbs . The normal physiological blood flow is anterograde , flowing from the periphery towards the heart , so that the evidence of an opposite , retrograde flow might indicate a pathology . The presence of a reflux is likewise of note ; a reflux when not isolated in a vein ( as simply retrograde ) , means that the blood flow is bi @-@ directional where once the flow had been only anterograde . 
