Predictive value of a negative computed tomographic scan in 100 patients with rectal carcinoma

The predictive value of a negative computed tomographic (CT) scan was assessed in a group of 100 patients with rectal carcinoma by correlating operative findings and pathologic stages in the patients who had no evidence of extrapelvic metastases on a preoperative CT scan. Sixty-four patients (64 percent) had stage T3 or T4 tumors. Ten patients had unsuspected distant metastases for an overall negative predictive value of 90 percent. Seven patients had small liver metastases, and three had periaortic nodal metastases. Six of the patients with liver metastases had them completely resected at the original laparotomy. The predictive value of the CT scan diminished in the patients who were selected to receive full-dose preoperative radiation therapy and had a mean delay of 12 weeks between CT scan and laparotomy. The preoperative carcinoembryonic antigen levels were of no value in predicting the presence of distant metastases. These results show that a negative CT scan will fail to detect 10 percent of patients with small liver metastases or positive periaortic nodes.