| Subject | Contents |
| Definition | A CT scan X-rays the body from many angles. The X-ray beams are detected by the scanner and analyzed by a computer. The computer reconstructs the data into a picture of the body area being scanned. These images can be viewed on a monitor or reproduced as photographs. |
| Alternative Names | Helical or Spiral CT of the abdomen and pelvis |
| How the test is performed | The CT scanner is a free standing machine with a large hole in the center. The patient lies on a narrow table which slides into the hole. In most cases the patient will be on his back with his arms raised above his head. Patients who have difficulty with enclosed spaces such as those found with some MRI scanners do not usually have a problem with this type of test. A dye may be injected into a peripheral vein to better evaluate certain diseases and organs. The radiologist will decide if this is necessary. Please tell the technician or radiologist if you have any allergies or have had difficulty with prior CT examinations. It is very important that the patient remains still throughout the exam and holds his breath when asked. This will allow for better images. The actual scan time is usually about two minutes although the entire procedure usually takes much longer. |
| How to prepare for the test | The health care provider may advise fasting for 4 to 6 hours if contrast dye is to be used or if sedation is anticipated (consult the health care provider). The patient wears a hospital gown during the procedure. The patient may need to sign a consent form. Infants and children: The physical and psychological preparation you can provide for this or any test or procedure depends on your child's age, interests, previous experiences, and level of trust. For specific information regarding how you can prepare your child, see the following topics as they correspond to your child's age: infant test or procedure preparation (birth to 1 year) toddler test or procedure preparation (1 to 3 years) preschooler test or procedure preparation (3 to 6 years) schoolage test or procedure preparation (6 to 12 years) adolescent test or procedure preparation (12 to 18 years) |
| How the test will feel | The X-rays are painless. The primary discomfort may be from the need to lie still on the table. If a dye is needed to increase the contrast between different tissues or organs, it is administered by injection into a vein. The injection may sting and the site may be tender to the touch for several minutes. Dye injections may cause a warm sensation, a metallic taste and, in a few cases, hives . Very rarely more severe contrast reactions can occur. |
| Why the test is performed | An abdominal CT is a non-invasive way a physician can evaluate the patient's internal organs and tissues. The indications for the test are many and a full description is beyond the scope of this article. Some more common uses are for the evaluation of tumors, infections, renal stones or appendicitis.
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| Normal Values | |
| What abnormal results mean | The CT scan may show:abdominal aortic aneurysmabscessesacute bilateral obstructive uropathyacute cholecystitisacute unilateral obstructive uropathyAddison's diseaseamebic liver abscessappendicitisbilateral hydronephrosisbowel wall thickeningcarcinoma of the renal pelvis or uretercholangiocarcinomacholedocholithiasischolelithiasischronic bilateral obstructive uropathychronic cholecystitischronic pancreatitischronic unilateral obstructive uropathycomplicated UTI (pyelonephritis)cystinuriacystsechinococcusenlarged lymph nodes enlarged organs gastrointestinal or bowel obstructionglucagonomahairy cell leukemiahepatocellular carcinomahistoplasmosis; disseminatedHodgkin's lymphomaislet of Langerhans' tumormultiple endocrine neoplasia (MEN) IInephrocalcinosisnephrolithiasisnon-Hodgkin's lymphomaovarian cancerpancreatic abscesspancreatic carcinomapancreatic pseudocystpancreatitispheochromocytomaprimary hyperaldosteronismpyelonephritis; acutepyogenic liver abscessrenal cell carcinomaretroperitoneal fibrosissclerosing cholangitis spontaneous retroperitoneal hemorrhage stones (bladder, kidney, liver, gall bladder) testicular cancer tumors unilateral hydronephrosisureteroceleWilms' tumorWilson's diseaseZollinger-Ellison syndrome Additional conditions under which the test may be performed: acute renal failurealcoholic liver disease (hepatitis/cirrhosis)atheroembolic renal diseasechronic glomerulonephritischronic renal failureCushing's syndromeCushing's syndrome caused by adrenal tumorinjury of the kidney and uretermedullary cystic diseasemultiple endocrine neoplasia (MEN) Ipolycystic kidney diseasereflux nephropathyrenal artery stenosisrenal vein thrombosisskin lesion of histoplasmosis |
| What the risks are | CT scans and other X-rays are monitored and regulated to provide the minimum amount of radiation exposure needed to produce the image. CT scans provide low levels of radiation. During pregnancy , an abdominal CT scan is usually not recommended, because there is some evidence of risk to the fetus. The most common dye used is iodine based. A person who is allergic to iodine may experience nausea , sneezing , vomiting , itching , or hives . Rarely, the dye may cause anaphylaxis (a life-threatening allergic response ). |
| Special considerations | A CT scan provides a better picture of soft tissues (internal organs) than conventional X-rays. The benefits of an abdominal-retroperitoneal CT scan usually far outweigh the risks of radiation exposure. |
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