Abdominal 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.

  The health care provider may inject a dye into one of your veins. This helps certain diseases and organs show up better on the images.

  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

  Certain exams require a special dye, called contrast, to be delivered into the body before the test starts. Contrast can highlight specific areas inside the body, which creates a clearer image.

  Contrast can be given through a vein (IV) in your hand or forearm. If contrast is used, you may also 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). The test may be used to:

  • Study blood vessels
  • Identify masses and tumors, including cancer
  • Look for infections, kidney stones, or appendicitis
• What abnormal results mean

  The CT scan may show the following:

  • Abdominal aortic aneurysm
  • Abscesses
  • Acute bilateral obstructive uropathy
  • Acute cholecystitis
  • Acute unilateral obstructive uropathy
  • Addison's disease
  • Amebic liver abscess
  • Appendicitis
  • Bilateral hydronephrosis
  • Bowel wall thickening
  • Carcinoma of the renal pelvis or ureter
  • Cholangiocarcinoma
  • Choledocholithiasis
  • Cholelithiasis
  • Chronic bilateral obstructive uropathy
  • Chronic cholecystitis
  • Chronic pancreatitis
  • Chronic unilateral obstructive uropathy
  • Complicated UTI (pyelonephritis)
  • Cystinuria
  • Cysts
  • Echinococcus
  • Enlarged lymph nodes
  • Enlarged organs
  • Gastrointestinal or bowel obstruction
  • Glucagonoma
  • Hairy cell leukemia
  • Hepatocellular carcinoma
  • Histoplasmosis; disseminated
  • Hodgkin's lymphoma
  • Islet of Langerhans' tumor
  • Multiple endocrine neoplasia (MEN) II
  • Nephrocalcinosis
  • Nephrolithiasis
  • Non-Hodgkin's lymphoma
  • Ovarian cancer
  • Pancreatic abscess
  • Pancreatic carcinoma
  • Pancreatic pseudocyst
  • Pancreatitis
  • Pheochromocytoma
  • Primary hyperaldosteronism
  • Pyelonephritis - acute
  • Pyogenic liver abscess
  • Renal cell carcinoma
  • Retroperitoneal fibrosis
  • Sclerosing cholangitis
  • Stones (bladder, kidney, liver, gall bladder)
  • Testicular cancer
  • Tumors
  • Unilateral hydronephrosis
  • Ureterocele
  • Wilms' tumor
  • Wilson's disease
  • Zollinger-Ellison syndrome

  Additional conditions under which the test may be performed include the following:

  • Acute renal failure
  • Alcoholic liver disease (hepatitis/cirrhosis)
  • Atheroembolic renal disease
  • Chronic glomerulonephritis
  • Chronic renal failure
  • Cushing syndrome
  • Cushing syndrome caused by adrenal tumor
  • Injury of the kidney and ureter
  • Medullary cystic kidney disease
  • Multiple endocrine neoplasia (MEN) I
  • Polycystic kidney disease
  • Reflux nephropathy
  • Renal artery stenosis
  • Renal vein thrombosis
  • Skin lesion of histoplasmosis
• 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.

• References

  Pickhardt PJ. Diagnostic imaging procedures in gastroenterology. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 135.

Review Date: 2/23/2009

Reviewed By: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.