Phlebography is primarily performed to diagnose deep vein thrombosis—a condition in which clots form in the veins of the leg that can lead to pulmonary embolism in which those clots break off, travel to the lungs and pulmonary artery. Phlebography can also be used to distinguish blood clots from obstructions in the veins, to evaluate congenital vein problems, to assess the function of the deep leg vein valves, and to identify a vein for arterial bypass grafting. Ultrasound has replaced phlebography in many cases; but phlebography is the "gold standard" or the best test by which others are judged, but not used as a standard practice.
Phlebography is usually not performed in patients with kidney (renal) problems.
Phlebography, also called venography, ascending contrast phlebography, or contrast phlebography, is an invasive diagnostic test that provides a constant image of leg veins on a fluoroscope screen. Phlebography identifies the location, extent, and degree of attachment of 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, after noninvasive tests have failed to identify the disease.
Phlebography 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.
Phlebography 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.
Phlebography takes between 30 to 45 minutes and can be done in a physician's office, a laboratory, or a hospital. During the procedure, the patient lies on a tilting xray table. The area where the catheter will be inserted is sometimes 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 may also 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 (tourniquet) may be tied around the ankle or below the knee of the side into which the dye is injected, 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 is 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, although the test may be 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 their doctor.
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.
Phlebography 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 phlebography results show proper blood flow through the leg veins.
Abnormal phlebography results show well-defined filling defects in veins. Findings include:
- blood clots
- consistent filling defects
- an abrupt end of a test dye column
- major deep veins that are unfilled
- dye flow that is diverted (These results confirm a diagnosis of deep vein thrombosis.)
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 phlebography, 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.
Health care team roles
A phelbography is generally performed in a hospital, or in an outpatient or freestanding facility. A qualified xray lab technician, nurse, or doctor might perform the test, with a radiologist reading or interpreting the results that are presented to the patient either directly, or through the primary care physician. Because the patient will be asked to lie on the x-ray table and a vein is punctured in order for the test to be taken, an attending nurse or other medical assistant in addition to the person performing the test should be present to assist when necessary. A professional will be prepared to handle any possible complication, especially if a patient experiences an allergic reaction to the test medium.
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Stéphanie Islane Dionne