To analyze the rates of missed diagnosis of digital rectal examination and colonoscopy and to explore the importance of colonoscopy combining digital rectal examination in patients with low rectal polyps.

Two hundred and forty-four patients receiving colonoscopy and digital rectal examination at the same time were retrospectively evaluated. The differences of missed diagnosis between the two methods were assessed by the Chi-square test.

One hundred and forty-three polyps in 89 patients were diagnosed and resected in our hospital. The mean polyp diameter was (0.59±0.35) cm. Ninty-four polyps in 65 patients were found located less than 7 cm to anus. Among them, 23 polyps in 15 patients were missed diagnosis with digital rectal examination, and the missed diagnosis rate was 24.5%; 38 polyps in 29 patients were with colonoscopy, the missed diagnosis rate was 40.4%. The rate of missed diagnosis by digital rectal examination was lower than colonoscopy, χ²=5.460, P=0.019. According to subgroup analyses, small polyps, flat polyps and multiple polyps tended to be missed diagnosis. The rate of missed diagnosis of colonoscopy operated by junior endoscopists was significantly higher than that operated by experienced endoscopists. The missed rate of digital rectal examination for <2 minutes was significantly higher than that for ≥2 minutes. The missed rate of colonoscopy operated for <35 minutes was significantly higher than that operated for ≥35 minutes. The rate of missed diagnosis of colonoscopy was significantly higher than digital rectal examination in examining polyps located<3 cm from anus. All the above differences were statistically significant, P<0.05.

Both colonoscopy and digital rectal examination may result in missed polyps. The rate of missed diagnosis is associated with polyp size, shape, number, pathology, operating physician, and the time of examination. Using colonoscopy combined digital rectal examination can reduce the missed diagnosis rate of low rectal polyps.