Abdominal CT scan

Definition

An abdominal CT scan is an imaging method that uses x-rays to create cross-sectional pictures of the belly area. CT stands for computed tomography.

See also: CT scan

Alternative Names

CT of the abdomen

How the test is performed

You will be asked to lie on a narrow table that slides into the center of the CT scanner. Usually, you will lie on your back with your arms raised above the head.

Certain exams require a special dye, called contrast, to be delivered into the body before the test starts. Contrast helps certain diseases and organs show up better on the images. Contrast can be given through a vein (IV) in your hand or forearm. In some cases, you may be asked to drink a solution containing the dye.

Once inside the scanner, the machine's x-ray beam rotates around you. Small detectors inside the scanner measure the amount of x-rays that make it through the abdomen. A computer takes this information and creates several individual images, called slices.

You must be still during the exam, because movement causes blurred images. You may be told to hold your breath for short periods of time.

The actual scan time only takes a few minutes, although the entire procedure usually takes much longer.

How to prepare for the test

If contrast is used, you may be asked not to eat or drink anything for 4-6 hours before the test.

Before receiving the contrast, tell your health care provider if you take the diabetes medication metformin (Glucophage) because you may need to take extra precautions.

Some people have allergies to IV contrast and may need to take medications before their test in order to safely receive this substance.

If you weigh more than 300 pounds, have your doctor contact the scanner operator before the exam. CT scanners have a weight limit. Too much weight can cause damage to the scanner's working parts.

Since x-rays have difficulty passing through metal, you will be asked to remove jewelry and wear a hospital gown during the study.

How the test will feel

Some people may have discomfort from lying on the hard table.

Contrast given through a vein (IV) may cause a slight burning sensation, a metallic taste in the mouth, and a warm flushing of the body. These sensations are normal and usually go away within a few seconds.

Why the test is performed

An abdominal CT rapidly creates detailed pictures of the structures inside the belly area (abdomen).

Your doctor may order this test to:

• Determine the cause of abdominal pain or swelling
• Diagnose or monitor cancerous tumors
• Diagnose a hernia
• Determine the cause of a fever
• Identify masses and tumors, including cancer
• Look for damage after an injury
• Look for infections, kidney stones, or appendicitis

Normal Values

What abnormal results mean

The abdominal CT scan may reveal certain cancers, including:

• Breast cancer
• Cancer of the renal pelvis or ureter
• Colon cancer
• Hepatocellular carcinoma
• Lymphoma
• Melanoma
• Ovarian cancer
• Pancreatic cancer
• Pheochromocytoma
• Renal cell carcinoma (kidney cancer)
• Testicular cancer

The abdominal CT scan may show problems with the gallblader, liver, or pancreas, including:

• Acute cholecystitis
• Alcoholic liver disease
• Cholelithiasis
• Pancreatic abscess
• Pancreatic pseudocyst
• Pancreatitis
• Sclerosing cholangitis

The abdominal CT scan may reveal the following kidney problems:

• Acute bilateral obstructive uropathy
• Acute unilateral obstructive uropathy
• Chronic bilateral obstructive uropathy
• Chronic unilateral obstructive uropathy
• Complicated UTI (pyelonephritis)
• Kidney stones
• Kidney swelling (hydronephrosis)
• Kidney or ureter damage
• Polycystic kidney disease
• Uterocele

Abnormal results may also be due to:

• Abdominal aortic aneurysm
• Abscesses
• Appendicitis
• Bowel wall thickening
• Retroperitoneal fibrosis
• Renal artery stenosis
• Renal vein thrombosis

What the risks are

CT scans and other x-rays are strictly monitored and controlled to make sure they use the least amount of radiation. CT scans do create low levels of ionizing radiation, which has the potential to cause cancer and other defects. However, the risk associated with any individual scan is small. The risk increases as numerous additional studies are performed.

In some cases, a CT scan may still be done if the benefits greatly outweigh the risks. For example, it can be more risky not to have the exam, especially if your health care provider thinks you might have cancer.

The most common type of contrast given into a vein contains iodine. If a person with an iodine allergy is given this type of contrast, nausea or vomiting,sneezing, itching,or hives may occur. Let your doctor know if you have ever had an allergic reaction to injected contrast dye.

If you absolutely must be given such contrast, your doctor may choose to treat you with antihistamines (such as Benadryl) or steroids before the test.

The kidneys help filter the iodine out of the body. Therefore, those with kidney disease or diabetes should receive plenty of fluids after the test, and be closely monitored for kidney problems. If you have diabetes or are on kidney dialysis, talk to your health care provider before the test about your risks.

Rarely, the dye may cause a life-threatening allergic response called anaphylaxis. If you have any trouble breathing during the test, you should notify the scanner operator immediately. Scanners come with an intercom and speakers, so the operator can hear you at all times.

Special considerations

A CT scan provides a better picture of internal organs than traditional x-rays. The benefits of an abdominal CT scan usually far outweigh the risks of radiation exposure.

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References

Shaw AS, Dixon AK. Multidetector computed tomography. In: Adam A, Dixon AK, eds. Grainger & Allison's Diagnostic Radiology: A Textbook of Medical Imaging. 5th ed. New York, NY: Churchill Livingstone; 2008:chap 4.