Risk in primary care of colorectal cancer from new onset rectal bleeding: 10 year prospective study.

OBJECTIVE To measure the risk of colorectal cancer and adenoma with new onset rectal bleeding reported to primary care. DESIGN Cohort study. SETTING A rural general practice in the United Kingdom. PARTICIPANTS Patients aged 45 or more with new onset rectal bleeding, irrespective of other symptoms. MAIN OUTCOME MEASURES Percentage of participants in whom colorectal cancer or colonic adenoma was identified after investigation of the bowel. RESULTS During a 10 year period, 265 patients reported new rectal bleeding. Of these, 15 (5.7%, 95% confidence interval 3.2% to 9.2%) had colorectal cancer, and 13 (4.9%, 2.6% to 8.4%) had colonic adenoma. Only two of the patients with cancer had had diarrhoea. CONCLUSIONS One in 10 patients aged 45 or more with new onset rectal bleeding had colonic neoplasia, so investigation of the bowel should be offered to all such patients, whether or not they have other symptoms.