Effectiveness of polyethylene glycol antegrade gut lavage bowel preparation for colonoscopy—timing is the key!

PURPOSE: Polyethylene glycol gut lavage is an effective bowel preparation for colonoscopy. The quality of the preparation is not uniform however, and most studies report a rate of suboptimal cleansing of 10 percent or more. One of the possible reasons for a poor preparation is the length of time between the lavage and the examination. The aim of this study was to assess the effect of timing of polyethylene glycol gut lavage on the quality of the preparation achieved. METHODS: Patients referred for elective outpatient colonoscopy with afternoon appointments were randomized to take polyethylene glycol gut lavage either the same morning as their examination (Group 1) or the afternoon of the day before (Group 2). The colonoscopist was unaware of the preparation timing until after the examination was over. During the examination the endoscopist scored the quality of bowel preparation in the cecum, ascending colon, and transverse and left colon. Patient demographics and clinical data were recorded. RESULTS: There were 157 patients in Group 1 (colonoscopy complete in 152 patients) and 160 in Group 2 (colonoscopy complete in 159 patients). The groups were similar in age and gender, indication for colonoscopy, and previous colonic surgery. Patients who drank gut lavage on the morning of their colonoscopy had a greatly better preparation in all areas of the colon than the patients who took their preparation the night before. In the cecum, 97 Group 1 patients had an excellent preparation (vs. 14 Group 2 patients), 45 had a good preparation (vs. 103 Group 2 patients), and 10 had a fair preparation (vs. 33 Group 2 patients). In the ascending colon, numbers of patients with excellent, good, fair, and poor results were 103, 45, 5, and 0 for Group 1 and 12, 107, 32, and 7 for Group 2. Results in the transverse and left colons were 102, 50, 5, 0 and 93, 55, 7, 2 for Group 1 and 15, 116, 27, 5 and 18, 114, 24, 3 for Group 2, respectively. CONCLUSION: The timing of administration of polyethylene glycol-based gut lavage is a major determinant of the quality of the bowel preparation achieved.