Comparison of precontrast, postcontrast, and delayed CT scanning for the staging of rectal carcinoma.

An attempt is made to establish the most appropriate examination procedure for staging rectal carcinoma by computed tomography (CT). Twenty-two patients with rectal carcinoma had CT performed preoperatively. The following three CT sequences were performed in all patients: a precontrast scan with 10-mm slices; a rapid sequence scan with 5-mm slices during bolus injection of contrast medium; and a postcontrast scan after a 10-min delay. Tumor extension and the presence of perirectal lymph nodes were evaluated separately and independently in all three CT sequences according to the TNM classification. All patients had surgical follow-up and the CT scans were compared to the surgical and histopathological findings. There was no significant difference in diagnostic outcome in the three CT procedures. Information obtained by frontal and lateral scout views were compared, and the lateral scout view proved more informative than the frontal scout view. For staging rectal carcinoma, narrow slice scanning and intravenous contrast media are superfluous and should be reserved for special cases. We recommend the use of lateral scout views.