Synonyms Abdomen, CT; CT, Lower Abdomen; CT, Total Abdomen; CT, Upper Abdomen

Procedure Commonly Includes CT scan of liver, spleen, kidneys, pancreas, aorta, retroperitoneum, gastrointestinal tract, pelvis. Note: In some departments, a request for a CT study of the abdomen will yield a study extending inferiorly to the pubic symphysis. In others, the study will extend only to the pelvic brim. See Computed Transaxial Tomography, Pelvis.

Indications Diagnosis and/or evaluation of cysts, tumors, masses, aneurysm, metastases, abscesses, and trauma. The modality is also often used for staging of known tumors. Suspected pancreatic or adrenal pathology may be a good indication for a spiral/helical examination. The evaluation of the liver may benefit from a dynamic CT exam. These decisions are best made by the radiologist when he/she is familiar with the clinical data.

Contraindications Patient cooperation is of the utmost importance as the examination requires the patient to remain motionless for the duration of the study. The time of the study will vary from 20-40 minutes depending on the equipment being used. Children and uncooperative adults may require sedation.

Patient Preparation Patient's oral intake restricted to fluid only for 4 hours prior to the examination. Medication schedule should not be interrupted. Should the patient have recently undergone a barium examination of the gastrointestinal tract, a digital radiograph obtained with the scanner prior to commencement of the procedure may be helpful in excluding the presence of barium within the bowel. The latter may produce significant artifact and thus render the study nondiagnostic. Where possible, all CT scan studies of the abdomen should be performed prior to normal GI barium studies. A recent serum creatinine is requested on all patients 60 years of age and older, patients with known significant atherosclerotic disease, diabetes mellitus, or with pre-existing renal disease. Intravenous contrast material is routinely administered for this examination. Physician may opt to omit intravenous contrast. Patients undergoing a CT study of the abdomen are requested to drink approximately 450 mL of a dilute barium solution (approximately 1% barium) commencing 1 hour prior to the examination. Inclusion of the pelvis in this examination requires further patient preparation. See Computed Transaxial Tomography, Pelvis.

Special Instructions CT scan of the abdomen may be requested by a practicing physician. The abdominal area of interest should be specified along with pertinent clinical history. This will allow the diagnostic radiologist to tailor the examination for maximum diagnostic yield. For example, studies being performed for detection of renal calculi should be performed without contrast material, as the contrast, when excreted from the kidney, will mask the presence of small calculi within the collecting system. Adequate evaluation of small structures within the abdomen may require modification of technique such as thin slices or overlapping slices. A further example would be in the evaluation of the liver for primary or metastatic tumor. Maximum yield in the demonstration of such abnormalities requires examination both with and without contrast material.

Equipment This examination may be performed on any one of many commercially available computerized tomography scanners.

Technique Standard examination of the abdomen consists of 1 cm contiguous slices obtained from the dome of the diaphragm to the pelvic brim or pubic symphysis depending upon whether one groups the pelvis with the abdomen or treats it separately.

Causes for Rejection Patients with residual barium within the GI tract from a prior conventional barium study - this nondilute barium produces considerable artifact rendering the examination suboptimal and often nondiagnostic, uncooperative patients who are not candidates for sedation/anesthesia

Turnaround Time A verbal telephone report of the scan will be given to the referring physician if specified. A written report will be available.

Additional Information Patients should be informed that the examination may take 45 minutes to 1 hour and that oral contrast and intravenous contrast are commonly required. If the pelvis is included with the abdominal CT study, rectal contrast material and placement of a vaginal tampon in the case of females may also be required. The patient's medical record should accompany the patient. This will furnish the radiologist with sufficient information to tailor the examination as he/she deems appropriate. For example, patients suspected of an adrenal adenoma may require thin (2 mm) slices through the adrenal glands for the detection of such an abnormality; if spiral/helical CT were available, this would be a good application.

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