Background: Colonoscopy is an effective surveillance for the diagnosis and screening of colorectal cancer (CRC). Prior to the procedure, people would take laxatives for a good visualization of bowel texture. Although a split-dose bowel preparation has become popular, many anesthesiologists are concerned about pulmonary aspiration.

Objective: To study the gastric residual volume and pH in patients taking split-dose bowel preparation as compared to those having laxatives on the day before the procedure.

Materials and Methods: One hundred patients were randomized equally into two groups, as A for a single-dose, and B for a split-dose regimen. All patients underwent endoscopy under standard anesthetic care. The total gastric residual volume was suctioned, and pH was measured through the endoscope. The surgical team was unaware of the study protocol. The quality of bowel cleansing was assessed by the endoscopist using the Boston Bowel Preparation Scale (BBPS).

Results: The bowel cleansing, the latency period, the endoscopist and patients’ satisfaction of single-and split-dose group were 7.06±1.4 and 8.14±1.1, 13.3±1.1 and 4.2±0.4 hours, 62.0% and 94.0%, and 90.0% and 74.0%, respectively. They all showed statistically significant differences between the two groups (p<0.05).

Conclusion: The gastric residual volume and pH were not different between the split and single-dose preparations. Therefore, it might not increase the risk of aspiration pneumonitis. However, the split-dose technique was more effective in colon cleansing, patients’ tolerability, acceptability, and compliance than the preparations administered entirely the day or evening before the surgical procedure.