Text 4. Ct scan of the abdomen or pelvis

Although the CT scan is a relatively new technique, it provides such valuable information that it is frequently used in diagnosing a variety of disorders, including tumours, cysts, lesions, abscesses, and broken blood vessels.

CT scans are performed in the radiology department by nurses or technicians specially trained to operated CT scanning equipment. The scanning machine is very large and looks like a giant, six-foot doughnut. The hole in the doughnut is designed to be big enough for a person lying on the x-ray table to be moved back and forth through it.

An x-ray tube or "camera" is mounted inside a ring surrounding the doughnut hole. As the x-ray tube rotates around your body, a computer in the next room measures from each angle the amount of energy absorbed by your body tissue. By analyzing this information, the computer converts it into a picture of the internal organs of your body, showing very subtle differences in the densities. (The differences in densities appear as different shades of grey similar to a black and white photograph). The picture, which appears first on the computer's screen, is different from a regular x-ray because it shows a cross-section of your body (looking down through your body) from the front, back, or side.

After the computer has analyzed one picture, the table you are lying on will be moved slightly so that a picture of a different cross-section can be made. A CT scan usually involves from 10 to 30 different pictures, depending on how large an area is being examined.

For a CT scan of the abdomen or pelvis, you will be asked to not eat or drink anything the night before the examination. About an hour before the scan, you will be asked to drink two glasses of contrast dye, a special solution used to help highlight certain internal structures. If you are allergic to seafood or iodine, you may also be allergic to the contrast dye. Inform your nurse or doctor of your allergies before you drink the first glass of dye.

For the abdominal scan, you will be asked to drink two more glasses of the dye (unless you are allergic to it) just before the procedure begins. For a CT of the pelvis, you will not have to drink any more dye, but a tube will be inserted into your rectum and the dye will be given by an enema. You will be requested to hold this fluid in your rectum throughout the procedure.

You may feel warm or flushed from the dye, and you may have a strange metallic taste in your mouth. You may also experience nausea, but this usually doesn't last long. Many patients say that the greatest discomfort is the urge to urinate as the dye is filtered out of the bloodstream by the kidneys. Emptying your bladder before the scan begins can help to avoid this problem.

Once the scan begins, it is very important that you lie very still throughout the procedure. Try to make yourself as comfortable as possible before the test begins. Ask for a blanket if you are cold, or ask to have your knees propped up on pillows. For part or the entire scan, you may be asked to lie with your arms extended over your head. This can be very awkward position, but it is important that you are still during the test; otherwise portions of it may have to be repeated.

After you have been comfortably positioned on the table, the technician will go into an adjacent room where the computer that operates the scanner is located. He or she will be able to observe you through a window and give you instructions as needed.

The table will be positioned so that you move feet first into the scanner until your abdomen or pelvis is cantered within the ring of the machine. The table will be moved slightly forward for each additional picture. You will hear the sounds of the machine as the x-ray tube rotates around you, but there is no pain involved. Although each scan takes only a few seconds, there may be a delay of several minutes between each picture while the technician waits for the computer to compile the picture.

After the scan is over you can empty your bowel and bladder before returning to your room. You can then resume your normal activities and diet. You may be requested to drink extra fluids to help flush the dye out of your bloodstream.

A radiologist will examine the pictures from the scan and send a written report to your doctor. This information should be available within a few days.