Venography is the radiographic examination of the veins, according to WebMD. This procedure involves injecting a contrast dye and using X-ray to get clear images of the veins in the legs.
Doctors perform venography to diagnose deep vein thrombosis, a medical disease that causes blood clotting in the legs, according to Mayo Clinic. Less invasive tests such as ultrasound can confirm the presence of deep vein thrombosis. However, venography offers more accurate results than ultrasound, though it increases the chances of developing blood clots, notes WebMD. Also known as phlebography, venography is also helpful in assessing the function of deep vein valves, explains Encyclopedia of Surgery.