Characteristics of colorectal cancer that produce positive immunochemical occult blood test results on stool obtained by digital rectal examination.

OBJECTIVE: To clarify the clinicopathological features of colorectal cancer that show positive results on an immunochemical fecal occult blood test of stool obtained by digital rectal examination.
METHODS: In a cross-sectional study, 9952 subjects received both an immunochemical fecal occult blood test of stool obtained by digital rectal examination and colonoscopy annually over a nine-year period of medical checkups; 64 patients with colorectal cancer were identified. The study subjects comprised 39 patients with colorectal cancer who had positive results (positive group) and 25 patients with colorectal cancer who had negative results (negative group) on an immunochemical fecal occult blood test of stool obtained by digital rectal examination. The positive and negative groups were compared in terms of their individual factors, such as site, size, Dukes classification and histological type of the cancer lesions.
RESULTS: The prevalence of rectal cancers was higher in the positive group than in the negative group (P<0.05), but there were no differences between the two groups with respect to any other factors.
CONCLUSIONS: These findings indicate that stool obtained during the digital rectal examination is unsuitable for detecting fecal occult blood, especially for the detection of proximal colon neoplasms.