Split-dose bowel preparation for colonoscopy results in superior preparation quality. However, some endoscopy units remain hesitant to prescribe split-dose preparation given theoretical concerns about possible aspiration caused by gastric residual fluid when a second dose is given close to the time of endoscopy. Our aim was to compare gastric residual volume (GRV) in patients taking split-dose bowel preparation and those taking preparation the evening before colonoscopy.

We performed a prospective observational comparison of GRV among random inpatients undergoing same-day EGD and colonoscopy either after a split-dose bowel preparation or after a bowel preparation the prior evening.

GRV was measured in 150 patients undergoing EGD and colonoscopy: 75 who completed a split-dose bowel preparation 2 to 3 hours before endoscopy and 75 who completed the bowel preparation regimen the prior evening. The mean GRV 2 to 3 hours after the last ingestion of bowel preparation among split-dose group patients was 21 ± 24 mL (± standard deviation; range, 0 to 125 mL), which was not different from the mean GRV of 24 ± 22 mL (range, 0 to 135 mL) in patients who ingested the preparation the prior evening (P = .08). GRV had no association with the presence of diabetes, gastroparesis, or opioid use.

GRV is the same after a split preparation and fasting for 2 to 3 hours or after preparation with overnight fasting. The data suggest that the risk of aspiration is identical after either preparation technique and thus that sedation for colonoscopy can be performed safely 2 hours after bowel preparation ingestion.