A Prospective Study of Factors Associated with Abdominal Pain in Patients during Unsedated Colonoscopy Using a Magnifying Endoscope

OBJECTIVE: With the advent of endoscopic treatment, the detailed diagnosis of colorectal neoplasms made using magnifying colonoscopy has become increasingly important. However, insertion difficulty causes pain in unsedated colonoscopy. The aim of this prospective observational study was to clarify the factors associated with a patient's pain in unsedated colonoscopy using a magnifying endoscope. METHODS: Patient pain was assessed using a numerical rating scale (0-10) immediately after the procedure. We defined 5 as mild enough pain that patients would not be reluctant to undergo another colonoscopy. Acceptable pain was defined as 5 or less and severe pain was defined as 8 to 10. Univariate and multivariate linear regression analyses were performed using the pain scale score as a dependent variable. RESULTS: A total of consecutive 600 patients undergoing unsedated colonoscopies were evaluated to assess their abdominal pain. The completion rate was 99.5% (597/600). The mean pain scale score was 3.88±2.38. The rate of acceptable pain was 80.5% (483/600). The rate of severe pain was 6.7% (40/600) including the incomplete cases. A comparison of polyp-positive and polyp-negative cases revealed no marked difference in patient pain (3.82±2.24 vs. 3.94±2.49, respectively; p=0.590) or insertion time (6.62±3.98 vs. 6.29±4.21, p=0.090), while more observation time was needed in polyp-positive cases than in polyp-negative ones (16.30±4.95 vs. 13.08±4.69, p<0.01). Univariate and multivariate linear regression analyses revealed that an older age, colectomy, antispasmodic agent use, and a small-diameter endoscope were significant factors associated with less patient pain. In particular, a small-diameter endoscope induces significantly more acceptable pain than a non-small diameter endoscope [85.63% (274/320) vs. 73.93% (207/280), p=0.00003]. CONCLUSION: Unsedated colonoscopy using a magnifying endoscope by an expert may result in acceptable pain levels. The use of an antispasmodic agent, particularly hyoscine N-butyl bromide, and a small-diameter endoscope are recommended for reducing abdominal pain during unsedated colonoscopy.