Computed Tomography Scan of the Abdomen
In abdominal CT scan, a body scanner delivers x-rays to the abdominal cavity at many different angles. A computer compiles this information to construct highly detailed, cross-sectional images of tissues and organs, which are displayed on a TV monitor and recorded on x-ray film.
In some cases, a contrast dye may be used to help define the major blood vessels and various abdominal structures on the images. Abdominal CT scans are useful for detecting abnormalities in the
- gallbladder and bile ducts,
- kidneys and urinary tract,
- adrenal glands,
- gastrointestinal (GI) tract,
- fallopian tubes,
- peritoneum (the membrane lining the abdomen) and retroperitoneum (the space behind this lining).
Spiral CT scanning, a variation that improves the visibility of blood vessels, may be used to evaluate patients suspected of having an aneurysm (abnormal outpouching) in the abdominal aorta, the largest artery in the body. After contrast dye is injected, the spiral CT scanner provides highly detailed three-dimensional constructs of the abdominal aorta, yielding accurate measurements of the size and extent of aortic aneurysms.
CT portography is a variation that may be used in patients suspected of having very small liver tumors. Contrast dye is injected through a catheter inserted into the femoral artery in the groin and threaded to the splenic artery, and a newer, faster type of CT scanner is used to examine the liver.
Purpose of the Abdominal CT Scan
- To detect cysts, abscesses, tumors, inflammation, obstructions, bleeding, and other abnormalities in various abdominal and pelvic organs—particularly when other, less invasive tests, such as ultrasound, have failed to yield a diagnosis.
- To identify blood clots or an aneurysm in the abdominal aorta and its branches.
- To stage and monitor tumors before and after treatment for cancer.
- To detect enlarged lymph nodes in the abdomen.
- To guide the placement of biopsy needles and other instruments for various medical procedures.
- To plan for and assess the results of surgery, such as organ transplants or gastric bypass.
Who Performs Abdominal CT Scan
Special Concerns about Abdominal CT Scan
- Pregnant women should not undergo this test because exposure to ionizing radiation may harm the fetus.
- Barium retained in the GI system from recent contrast x-rays, such as an upper GI series, may interfere with the results.
- People with allergies to iodine or shellfish may experience an allergic reaction to iodine-based contrast dyes.
- Elderly individuals with chronic dehydration or kidney impairment are at risk for renal failure induced by the contrast dye. To determine whether the dye can be administered safely, your doctor may perform a blood test to assess kidney function before the test.
- People who experience claustrophobia may find it difficult to undergo a CT scan, which takes place in a narrow, tunnel-like structure.
- This test may not be possible for severely overweight individuals (over 300 lbs).
Before Abdominal CT Scan
- Inform your doctor if you have an allergy to iodine or shellfish. You may be given a combined antihistamine-steroid preparation to reduce the risk of an allergic reaction.
- Tell your doctor if you suffer from claustrophobia. He or she may prescribe a sedative that can help you tolerate the procedure.
- If you are to undergo CT portography, be sure to inform your doctor if you are taking any anticoagulants. It may be necessary to discontinue these drugs prior to the procedure.
- If a contrast dye is to be used, you should fast for 4 hours before the test and drink large amounts of fluids on the day before the test to prevent dehydration. If a dye is not being used, avoid eating for 2 hours before the test.
- Just before the test, remove your clothes and any metal objects, including watches, hair clips, and jewelry, and put on a hospital gown.
What You Experience
- You are asked to lie on your back on a narrow table that is then advanced into the CT scanner.
- The scanner, which encircles you, takes pictures of your abdomen at different intervals and from various angles. The resulting images are then recorded on x-ray film.
- Remain still because any movement can distort the image on the scan. The examiner may advise you on how to control your breathing at several points during the procedure.
- If a contrast dye is used, it is either administered orally before the test or given during the test through an intravenous (IV) catheter inserted into a vein in your arm. (Upon injection of the dye, you may experience a brief flushing sensation and a metallic taste in the mouth.)
- The procedure usually takes less than 30 minutes.
Risks and Complications of Abdominal CT Scan
- Although radiation exposure is minimal, you will receive a higher dose of radiation than during standard x-ray procedures.
- Some people may experience an allergic reaction to the iodine-based contrast dye, which can cause symptoms such as nausea, sneezing, vomiting, hives, and occasionally a life-threatening response called anaphylactic shock. Emergency medications and equipment are kept readily available.
- Patients who are dehydrated or those with impaired kidney function may experience acute renal failure from infusion of the contrast dye. Adequate hydration before the test can reduce this risk.
After the Abdominal CT Scan
- If contrast dye was used, you are encouraged to drink clear fluids to avoid dehydration and help flush the dye out of your system.
- If you underwent CT portography, the catheter is removed and a pressure dressing is applied to the puncture site. A small sandbag is typically placed over the incision site for several hours to prevent bleeding. You will rest in a recovery room for about 4 to 8 hours to allow the arterial puncture site to seal completely; during this time, your vital signs will be monitored and you will be observed for signs of complications.
- You are free to resume your normal diet and activities.
- Blood may collect and clot under the skin (hematoma) at the dye injection site; this is harmless and will resolve on its own. For a large hematoma that causes swelling and discomfort, apply ice initially; after 24 hours, use warm, moist compresses to help dissolve the clotted blood.
- Delayed allergic reactions to the contrast dye, such as hives, rash, or itching, may appear 2 to 6 hours after the procedure. If this occurs, your doctor will prescribe antihistamines or steroids to ease your discomfort.
Abdominal CT Scan Results
- A physician will examine the CT scans and other test data for evidence of abnormalities.
- If a definitive diagnosis can be made based on the findings, appropriate medical or surgical treatment will be initiated.
- In some cases, additional diagnostic tests may be needed to further evaluate abnormal results.
The Johns Hopkins Consumer Guide to Medical Tests
Simeon Margolis, M.D., Ph.D., Medical Editor
Updated by Remedy Health Media