Computed Tomography (CT or CAT) Scan of the Abdomen

(Abdominal CT Scan)

Procedure overview

Computed tomography (CT or CAT scan) is a noninvasive diagnostic imaging procedure that uses a combination of X-rays and computer technology to produce cross-sectional images (often called slices), both horizontally and vertically, of the body. A CT scan shows detailed images of any part of the body, including the bones, muscles, fat, organs, and blood vessels. CT scans are more detailed than standard X-rays.

In standard X-rays, a beam of energy is aimed at the body part being studied. A plate behind the body part captures the variations of the energy beam after it passes through skin, bone, muscle, and other tissue. While much information can be obtained from a standard X-ray, a lot of detail about internal organs and other structures is not available.

In computed tomography, the X-ray beam moves in a circle around the body. This allows many different views of the same organ or structure. The X-ray information is sent to a computer that interprets the X-ray data and displays it in a two-dimensional (2D) form on a monitor.

CT scans may be done with or without "contrast." Contrast refers to a substance taken by mouth or injected into an intravenous (IV) line that causes the particular organ or tissue under study to be seen more clearly. Contrast examinations may require you to fast for a certain period of time before the procedure. Your doctor will notify you of this prior to the procedure.

CT scans of the abdomen can provide more detailed information about abdominal organs and structures than standard X-rays of the abdomen, thus providing more information related to injuries and/or diseases of the abdominal organs.

CT scans of the abdomen may also be used to visualize placement of needles during biopsies of abdominal organs or tumors or during aspiration (withdrawal) of fluid from the abdomen. CT scans of the abdomen are useful in monitoring tumors and other conditions of the abdomen before and after treatment.

Other related procedures that may be used to diagnose abdominal problems include abdominal X-rays, pancreas scan, liver scan, gallbladder scan, kidney scan, endoscopy procedures, such as colonoscopy, abdominal ultrasound, and abdominal angiogram. Please see these procedures for additional information.

Reasons for the procedure

The abdomen contains organs of the gastrointestinal, urinary, endocrine, and reproductive systems. A CT scan of the abdomen may be performed to assess the abdomen and its organs for tumors and other lesions, injuries, intra-abdominal bleeding, infections, unexplained abdominal pain, obstructions, or other conditions, particularly when another type of examination, such as X-rays or physical examination, is not conclusive.

A CT scan of the abdomen may also be used to evaluate the effects of treatment on abdominal tumors. Another use of abdominal CT is to provide guidance for biopsies and/or aspiration of tissue from the abdomen.

There may be other reasons for your doctor to recommend a CT scan of the abdomen.

Risks of the procedure

You may want to ask your doctor about the amount of radiation used during the CT procedure and the risks related to your particular situation. It is a good idea to keep a record of your past history of radiation exposure, such as previous CT scans and other types of X-rays, so that you can inform your doctor. Risks associated with radiation exposure may be related to the cumulative number of X-ray examinations and/or treatments over a long period of time.

If you are pregnant or suspect that you may be pregnant, you should notify your health care provider. Radiation exposure during pregnancy may lead to birth defects.

If contrast dye is used, there is a risk for allergic reaction to the dye. Patients who are allergic to or sensitive to medications should notify their doctor. Studies show that 85 percent of the population will not experience an adverse reaction from iodinated contrast; however, you will need to let your doctor know if you have ever had a reaction to contrast dyes or any kidney problems. A reported seafood allergy is not considered to be a contraindication for iodinated contrast. If you take metformin/Glucophage, or a related medication, you will be asked to stop taking the medication for at least 48 hours after the contrast is administered, as it may cause a condition called metabolic acidosis, or an unsafe change in your blood pH.

Patients with kidney failure or other kidney problems should notify their doctor. In some cases, the contrast dye can cause kidney failure, especially if the person is dehydrated or already has underlying kidney disease. The effects of kidney disease and contrast agents have attracted increased attention over the last decade, as patients with kidney disease are more prone to kidney damage after contrast exposure.

There may be other risks depending on your specific medical condition. Be sure to discuss any concerns with your doctor prior to the procedure.

Certain factors or conditions may interfere with the accuracy of a CT scan of the abdomen. These factors include, but are not limited to, the following:

• Metallic objects within the abdomen, such as surgical clips
• Barium in the intestines from a recent barium study
• Stool and/or gas in the bowel
• Total hip replacement

Before the procedure

• Your doctor will explain the procedure to you and offer you the opportunity to ask any questions about the procedure.
• If your procedure involves the use of contrast dye, you will be asked to sign a consent form that gives permission to do the procedure. Read the form carefully and ask questions if something is not clear.
• Notify the technologist if you have ever had a reaction to contrast dyes or if you are allergic to iodine.
• Generally, there is no fasting requirement prior to a CT scan, unless a contrast dye is to be used. Your doctor will give you special instructions ahead of time if contrast is to be used and if you will need to withhold food and drink.
• Notify your doctor of all medications (prescribed and over-the-counter) and herbal supplements that you are taking.
• Notify the technologist if you are pregnant or suspect you may be pregnant.
• Notify the technologist if you have body piercings on your chest and/or abdomen.
• Based on your medical condition, your doctor may request other preparations.

During the procedure

CT scans may be performed on an outpatient basis or as part of your stay in a hospital. Procedures may vary depending on your condition and your doctor's practices.

CT Scan

Generally, a CT scan of the abdomen follows this process:

1. You will be asked to remove any clothing, jewelry, or other objects that may interfere with the procedure.
2. If you are asked to remove clothing, you will be given a gown to wear.
3. If you are to have a procedure done with contrast, an intravenous (IV) line will be started in the hand or arm for injection of the contrast dye. For oral contrast, you will be given a liquid contrast preparation to swallow. In some situations, the contrast may be given rectally.
4. You will lie on a scan table that slides into a large, circular opening of the scanning machine. Pillows and straps may be used to prevent movement during the procedure.
5. The technologist will be in another room where the scanner controls are located. However, you will be in constant sight of the technologist through a window. Speakers inside the scanner will enable the technologist to communicate with and hear you. You will have a call button so that you can let the technologist know if you have any problems during the procedure. The technologist will be watching you at all times and will be in constant communication.
6. As the scanner begins to rotate around you, X-rays will pass through the body for short amounts of time. You will hear clicking sounds, which are normal.
7. The X-rays absorbed by the body's tissues will be detected by the scanner and transmitted to the computer. The computer will transform the information into an image to be interpreted by the radiologist.
8. It will be important that you remain very still during the procedure. You may be asked to hold your breath at various times during the procedure.
9. If contrast dye is used for your procedure, you will be removed from the scanner after the first set of scans has been completed. A second set of scans will be taken after the contrast dye has been administered.
10. If contrast dye is used for your procedure, you may feel some effects when the dye is injected into the IV line. These effects include a flushing sensation, a salty or metallic taste in the mouth, a brief headache, or nausea and/or vomiting. These effects usually last for a few moments.
11. You should notify the technologist if you feel any breathing difficulties, sweating, numbness, or heart palpitations.
12. When the procedure has been completed, you will be removed from the scanner.
13. If an IV line was inserted for contrast administration, the line will be removed.
14. You may be asked to wait for a short period of time while the radiologist examines the scans to make sure they are clear.

While the CT procedure itself causes no pain, having to lie still for the length of the procedure might cause some discomfort or pain, particularly in the case of a recent injury or invasive procedure, such as surgery. The technologist will use all possible comfort measures and complete the procedure as quickly as possible to minimize any discomfort or pain.

After the procedure

If contrast dye was used during your procedure, you may be monitored for a period of time for any side effects or reactions to the contrast dye, such as itching, swelling, rash, or difficulty breathing.

If you notice any pain, redness, and/or swelling at the IV site after you return home following your procedure, you should notify your doctor as this could indicate an infection or other type of reaction.

If you are given contrast by mouth, you may experience diarrhea or constipation after the procedure.

Otherwise, there is no special type of care required after a CT scan of the abdomen. You may resume your usual diet and activities unless your doctor advises you differently. Your doctor may give you additional or alternate instructions after the procedure, depending on your particular situation.