Alternate Names: Retroperitoneum CT; CT scan - abdomen

How Performed: The patient lies on a narrow table (gantry) that slides into the center of the scanner. The scanner looks like a tube surrounded by the imaging equipment. A contrast-media (dye) may be injected into a vein to help define certain tissues. The table will advance slightly (1/4 to 1/2 inch) between each scan to align for the next cross-section image. The technologist operating the computer may indicate when it is necessary to control breathing. A sound system is built into the machine to allow for communication with the patient during the test.

During the test, it is very important to remain still. If a patient is restless or traumatized, a sedative may be given. Each exposure takes a few seconds. The complete scan takes about 1 hour.

How To Prepare: 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. Sedatives may be administered if necessary. 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 experience, 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 It Feels: 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 cool or warm sensation, a metallic taste and, in a few cases, hives.

Risks: 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).

Why Performed: An abdominal (or retroperitoneal) CT may be recommended when there is a need to evaluate the soft tissue, including the organs, of the abdomen and/or retroperitoneal space.

The test may be indicated when there is abdominal injury; to determine the size, shape, and position of internal organs; to look for tumors, cysts, hemorrhage, or edema of the pancreas; to determine if a patient has liver disease or disease of the retroperitoneal space; to detect kidney masses; to determine the cause of unexplained stomach pain; or to evaluate the response to chemotherapy.

Normal Values: Organs are normal in size and position; no masses (aggregations of cells) or other abnormalities exist.

Abnormal Results: The CT scan may show:

• 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
• spontaneous retroperitoneal hemorrhage
• stones (bladder, kidney, liver, gall bladder)
• testicular cancer
• tumors
• unilateral hydronephrosis
• ureterocele
• Wilms’ tumor
• Wilson’s disease
• Zollinger-Ellison syndrome

• acute renal failure
• alcoholic liver disease (hepatitis/cirrhosis)
• atheroembolic renal disease
• chronic glomerulonephritis
• chronic renal failure
• Cushing’s syndrome
• Cushing’s syndrome caused by adrenal tumor
• injury of the kidney and ureter
• medullary cystic disease
• multiple endocrine neoplasia (MEN) I
• polycystic kidney disease
• reflux nephropathy
• renal artery stenosis
• renal vein thrombosis
• skin lesion of histoplasmosis

Cost:

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.