PURPOSE: We evaluated the accuracy of preoperative diagnostic examinations and determined whether patients with synchronous colorectal cancers differ from patients with a single colorectal malignancy in clinicopathologic factors, the possibility of early metachronous colorectal cancer, and postoperative outcome. METHODS: A retrospective evaluation of 1,780 patients with primary colorectal adenocarcinoma from 1987 to 1993 was performed. We divided patients into three groups: Group 1, single colorectal adenocarcinoma; Group 2, synchronous colorectal adenocarcinoma; and Group 3, early metachronous colorectal adenocarcinoma. RESULTS: There were 52 cases (3 percent) in Group 2 and 13 cases (1 percent) in Group 3 (<3 years from the index colorectal cancer operation). Differences in age, gender, and cancer-free rate among the three groups did not reached statistical significance. Compared with cancers in Group 1, significantly more proximal tumor locations and early cancer stage were noted for the second and third cancers in Group 2. In Group 3 a significantly more proximal tumor site was noted for the index colorectal cancer but cancer stage showed no significant difference from cancers in Group 1. Better histologic type was also noted in the index and second cancers in Group 2 than in cancers in Group 1. There was a higher incidence of associated benign adenoma in Group 2 (35 vs. 15 percent in Group 1). The positivity rate of Group 2 was significantly higher by preoperative colonoscopy (71 percent) and incidental findings at surgery (58 percent) than barium enema examination (30 percent). CONCLUSION: Preoperative barium enema examination was an unsatisfactory tool for detecting synchronous tumors. Preoperative colonoscopy demonstrated a higher positivity rate, but it still failed to detect nearly 30 percent of cases with synchronous tumors. Intraoperative palpation of the whole colorectum could detect nearly 60 percent of unexpected synchronous tumors. We believe both colonoscopy and intraoperative palpation of the whole colorectum are crucial to the early detection of synchronous colorectal cancer.
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