A Venogram is special test that studies the veins in your body, usually the legs, for blood clots. The test takes about 1 hour. The radiologist will place a small needle into a vein on the top area of your foot. A tourniquet is placed around your ankle and a contrast (dye-like substance) is injected. This injection may cause a brief sensation of warmth or cause a bitter taste in your mouth. These are normal feelings. The contrast is carried along with the blood flow and can visualize, on x-ray, the blood vessels or veins in that part of you body. A series of x-rays will be taken before the needle is removed.