A computerized tomography (CT) urogram is an imaging exam used to evaluate the urinary tract. The urinary tract includes the kidneys, bladder and the tubes (ureters) that carry urine from the kidneys to the bladder.

A CT urogram uses X-rays to generate multiple images of a slice of the area in your body being studied, including bones, soft tissues and blood vessels. These images are then sent to a computer and quickly reconstructed into detailed 2D images.

During a CT urogram, an X-ray dye (iodine contrast material) is injected into a vein in your hand or arm. The dye flows into the kidneys, ureters and bladder, outlining each of these structures. X-ray pictures are taken at specific times during the exam, so your doctor can clearly see your urinary tract and assess how well it's working.

A CT urogram is used to examine the kidneys, ureters and bladder. It lets your doctor see the size and shape of these structures to determine if they're working properly and to look for any signs of disease that may affect your urinary system.

Your doctor may recommend a CT urogram if you have signs and symptoms — such as pain in your side or back or blood in your urine (hematuria) — that may be related to a urinary tract disorder.

A CT urogram may be helpful in diagnosing urinary tract conditions such as:

• Kidney stones
• Bladder stones
• Complicated infections
• Tumors or cysts
• Cancer
• Structural problems

With a CT urogram, there's a slight risk of an allergic reaction to the contrast material. Reactions are generally mild and easily managed by medication. They include:

• A feeling of warmth or flushing
• Nausea
• Itching
• Hives
• Pain near the injection site

A single CT urogram carries no risk of developing cancer after radiation exposure. But, multiple tests or radiation exposures may cause a slightly increased cancer risk. Typically, the benefit of an accurate diagnosis far outweighs this risk. Work continues on ways to reduce radiation exposure during a CT urogram test.

If you are pregnant or think that you may be pregnant, tell your doctor before having a CT urogram. Though the risk to an unborn baby is small, your doctor may consider whether it's better to wait or to use another imaging test.

Before a CT urogram, tell your health care team if you:

• Have any allergies, particularly to iodine
• Are pregnant or think you might be pregnant
• Have had a previous severe reaction to X-ray dyes
• Are taking any medications, such as metformin (Fortamet, Glucophage, others), nonsteroidal anti-inflammatory drugs (NSAIDs), anti-rejection drugs or antibiotics
• Have had a recent illness
• Have a medical condition, such as heart disease, asthma, diabetes, kidney disease or a prior organ transplantation

You may be asked to drink water before a CT urogram and not to urinate until after the procedure. This expands your bladder. But, depending on your condition, guidelines about what to eat and drink before your CT urogram may vary.

Before your CT urogram, a member of your health care team may:

• Ask you questions about your medical history
• Check your blood pressure, pulse and body temperature
• Ask you to change into a hospital gown and remove jewelry, eyeglasses and any metal objects that may obscure the X-ray images

During a CT urogram

For a typical CT urogram, you lie on your back on an exam table, though you may be asked to lie on your side or stomach. Straps and pillows may be used to help you maintain the correct position and keep still during the exam. You may be asked to change positions during the CT urogram.

An IV line is placed into a vein in your hand or arm through which the X-ray dye is injected. You may feel a warm, flushed sensation when the dye is injected and notice a metallic taste in your mouth for a minute or two. The contrast material may briefly make you feel like you have to urinate.

Before the exam begins, the table moves quickly through the scanner to determine the correct starting position for your scans. For the actual CT urogram, the table moves slowly through the machine while the images are taken. If needed, the machine may make several passes.

The machine makes slight buzzing and clicking sounds while it takes pictures. To keep the images from blurring, the technician may ask you to hold your breath for a few seconds during the scanning.

After the CT urogram is complete, the technician checks the images for quality while you wait.

After a CT urogram

When the test is done, the IV line is removed from your arm and the IV entry point is covered with a dressing. Most people return to their usual activities after the test.

A doctor who specializes in reading X-rays (radiologist) reviews and interprets the X-ray images from your CT urogram and sends a report to your doctor. Plan to discuss the results with your doctor at a follow-up appointment.