venography

Venography is an x-ray test that provides an image of the leg veins after a contrast dye is injected into a vein in the patient's foot.

Venography is primarily performed to diagnose deep vein thrombosis (a condition that can lead to pulmonary embolism). It is the standard procedure used to detect this type of disorder. Venography also can be used to distinguish blood clots from obstructions in the veins, to evaluate congenital vein problems, to see how the deep leg vein valves are working, and to identify a vein for arterial bypass grafting.

Venography usually is not performed in patients with kidney (renal) problems.

Venography (also called phlebography, ascending contrast phlebography, or contrast venography) is an invasive diagnostic test that provides a constant image of leg veins on a fluoroscope screen. Venography identifies the location, extent, and degree of attachment of the blood clots, and enables the condition of the deep leg veins to be assessed. It is especially useful when there is a strong suspicion of deep vein thrombosis, but non-invasive tests have failed to identify the disease.

Venography is the most accurate test for detecting deep vein thrombosis. It is nearly 100% sensitive and specific in making this diagnosis (pulmonary embolism is diagnosed in other ways). Accuracy is crucial since deep vein thrombosis can lead to pulmonary embolism, a condition that can be fatal.

Venography is not used often, however, because it is painful, expensive, exposes the patient to a fairly high dose of radiation, and can cause complications. In about 5% of cases, there are technical problems in conducting the test. In addition, the test is less accurate in diagnosing problems below the knee. Venography takes between 30-45 minutes and can be done in a physician's office, outpatient center, or a hospital.

In 2003, a report said that computed tomography (CT) scanning could be used to diagnose pulmonary embolism and deep veinous thrombosis in one examination. By combining CT angiography and CT venography, researchers could look for both conditions in one procedure with high-speed CT scanners. The procedure was quick and delivered a reduced radiation dose. However, it has not become accepted as a replacement for traditional venography and is only preferred if the patient is clinically stable and requires immediate diagnosis and treatment.

During the procedure, the patient lies on a tilting x-ray table. The area where the catheter will be inserted will be shaved, if necessary, and cleaned. Sometimes a local anesthetic is injected to numb the skin at the site of the insertion. A small incision may be required to make a point for insertion. The catheter is inserted and the contrast solution (or dye) is slowly injected. Injection of the dye causes a warm, flushing feeling in the leg that may spread through the body. The contrast solution also may cause slight nausea. About 18% of patients experience discomfort from the contrast solution.

In order to fill the deep venous system with dye, a tight band (or tourniquet) may be tied around the ankle of the foot the dye is injected into, or the lower extremities may be tilted. The patient is asked to keep the leg still. The doctor also observes the movement of the solution through the vein with a fluoroscope. At the same time, a series of x rays are taken. When the test is finished, fluid is injected to clear the dye from the veins, the catheter is removed, and a bandage is applied over the site of the injection.

Fasting or drinking only clear liquids is necessary for four hours before the test. However, sometimes the test is done in an emergency even if the patient has eaten. The contrast solution contains iodine, to which some people are allergic. Patients who have allergies or hay fever, or have had a bad reaction to a contrast solution, should tell the doctor. A sedative, such as diazepam (Valium), may be prescribed to help the patient relax.

Patients should drink large amounts of fluids to flush the remaining contrast solution from their bodies. The area around the incision will be sore for a few days. If there is swelling, redness, pain, or fever, the doctor should be notified. Pain medication may be needed. In most cases, the patient can resume normal activities the next day.

Venography also can cause complications such as phlebitis, tissue damage, and the formation of deep vein thrombosis in a healthy leg. A rare side effect in up to 8% of cases is a severe allergic reaction to the dye. This usually happens within 30 minutes after injection of the dye and requires medical attention.

Normal venography results show proper blood flow through the leg veins.

Abnormal venography results show well-defined filling defects in veins. Findings include:

Contrast solution — A liquid dye injected into the body that allows veins to be seen by x rays. Without the dye, the veins could not be seen on x rays.

Deep vein thrombosis — The development or presence of a blood clot in a vein deep within the leg. Deep vein thrombosis can lead to pulmonary embolism.

Invasive — A diagnostic test that invades healthy tissue; in the case of venography, through an incision in a healthy vein.

Pulmonary embolism — An obstruction of a blood vessel in the lungs, usually due to a blood clot, that blocks a pulmonary artery. Pulmonary embolism can be very serious and in some cases is fatal.

These results confirm a diagnosis of deep vein thrombosis.

Abella, H.A. "CT Dose Techniques Address PE, DVT—Indirect Venography and Collimation Changes Reduce Exposure." Diagnostic Imaging November 1, 2003.

1. angiography of a vein or veins.

2. the graphic recording of the venous pulse; called also venography.