Duplex ultrasonography (an ultrasound) has vastly improved our ability to diagnose and treat venous disorders. Appropriately trained individuals looking for the right problem must perform the ultrasound. A negative ultrasound for clots does not mean the patient does not have a significant venous disease. They may have reflux.
Today, we are using ultrasound in a much more sophisticated way, looking not just for "clot" but also for "reflux".
Reflux is a condition where the blood in the vein travels away from, rather than towards the heart. This abnormality results in leg heaviness, tiredness and ultimately enlarged varicose veins. The conditions may lead to problems such as skin ulceration, discoloration or infection. Left untreated, venous reflux can be a very disabling condition.