A venogram is a diagnostic test that uses x-ray images to track the flow of a special dye through the body's veins. Radiologists can perform the test to look for blood clots, tumors, and abnormally wide or narrow veins. In addition, a venogram may be taken to identify healthy blood vessels that can be transplanted into the heart or neck for a bypass procedure. The test is usually quick, painless, and highly effective at discovering physical abnormalities that cannot be easily studied with other diagnostic tools.
When a patient is scheduled for a venogram, he or she is usually asked to avoid eating food or drinking anything but water on the day of the test. A thorough medical history is taken to make sure the procedure will be safe and that the patient is not allergic to the dye. The patient is fitted with a hospital gown and brought to a radiology lab for testing. He or she lies down on a table so a specialist can sterilize the injection site, which may be in the foot, groin, arm, or torso. A local anesthetic may be given to temporarily numb the site.
Once the patient is prepared, the radiologist injects a contrast dye containing an iodine or barium solution into a vein. The dye travels throughout the blood vessels near the injection site, leaving a trail that is easily detectable on x-ray images. A set of x-rays are then taken from several different angles. After the procedure, the radiologist may inject saline into a vein to dilute the dye and a blood thinner to prevent clotting. The patient is then transported to a hospital room and instructed to drink a lot of water to help flush the dye from his or her system.
Venogram images are carefully reviewed by a trained radiology specialist. He or she compares x-rays from different angles and identifies the size, location, and nature of abnormalities. If the dye's path is suddenly disrupted, the specialist can be fairly confident that a blood clot exists. Tumors and structural defects may be discovered if the dye follows an unusual path. In addition, veins that are ruptured, weak, or too wide can be detected based on the movements of the dye.
The most common reason for performing a venogram is to check for a condition called deep vein thrombosis (DVT). DVT is a large, quickly developing blood clot in one of the major blood vessels in the leg, which can disrupt blood flow to the heart and possibly lead to a heart attack or stroke. Ultrasounds and conventional x-rays are often insufficient in pinpointing the location and severity of DVT, but a venogram is usually very effective. Treatment decisions are made immediately following a venogram test to provide the best chances of recovery.