A renal venogram is a test to look at the veins in the kidney. It uses x-rays and a special dye (called contrast).

X-rays are a form of electromagnetic radiation like light, but of higher energy, so they can move through the body to form an image on film. Structures that are dense (such as bone) will appear white, air will be black, and other structures will be shades of gray.

Veins are not normally seen in an x-ray. That is why the special dye is needed. The dye highlights the veins so they show up better on x-rays.

See also: Renal arteriography

This test is done in a hospital. You will lie on an x-ray table. Local anesthetic is used, and you may ask for a sedative if you are anxious about the test.

The health care provider places a needle into a vein in the groin and then inserts a flexible tube called a catheter. This tube is moved through the groin vein until it reaches the vein in the kidney. The contrast dye flows through this tube. X-rays are taken as the dye moves through the kidney veins.

This procedure is monitored by fluoroscopy, a type of x-ray that creates images on a TV screen.

Once the images are taken, the catheter is removed and a bandage is placed over the wound.

You will be told to avoid food and drinks for about 8 hours before the test. Your doctor may tell you to stop taking aspirin or other blood thinners before the test. NEVER stop taking any medicine without talking to your doctor.

You will be asked to wear hospital clothing and to sign a consent form for the procedure. You will need to remove any jewelry from the area that is being studied.

Tell the health care provider if you:

• Are pregnant
• Have allergies to any medication, contrast dye, or iodine
• Have a history of bleeding problems

The x-ray table is hard and cold -- you may ask for a blanket or pillow. You may feel a sting when the anesthesia medicine is given and a burning feeling when the dye is injected. You may feel some pressure and discomfort as the catheter is positioned.

There may be tenderness and bruising at the site of the injection after the test.

The test is done to detect blood clot , tumors, and vein problems. The test may also be used to measure hormone levels produced by the kidney.

There should not be any clots or tumors in the kidney vein. The dye should flow quickly through the vein.

Abnormal results may be due:

• Blood clot that partially or completely blocks the vessel
• Kidney tumor
• Vein problem

See also: Renal vein thrombosis

Risks from this test may include:

• Allegic reaction to the contrast dye
• Bleeding
• Blood clots
• Injury to a vein

There is low-level radiation exposure. However, most experts feel that the risk of most x-rays is smaller than other risks we take every day. Pregnant women and children are more sensitive to the risks of the x-ray.

This test is rarely done. It has largely been replaced by CT scan and MRI.