The cleansing result of oral sodium phosphate is inversely correlated with time between the last administration and colonoscopy

Background There is some evidence that the timing of sodium phosphate (NaP) ingestion affects the cleansing result. The objective of this study was to evaluate the correlation of cleansing result with the timing of ingestion of NaP. Methods 214 consecutive outpatients scheduled to undergo colonoscopy were enrolled in the study. All patients filled out a detailed questionnaire concerning the execution of bowel cleansing. Concomitant with colonoscopy, patient characteristics were recorded and after the procedure the cleansing result was scored. The correlation between cleansing score and time from the last dose of NaP to colonoscopy was evaluated. For further analysis, patients were divided into three groups regarding the time lag from NaP taking to colonoscopy (group 1, 6 h or less; group 2, 6–12 h; group 3, 12 h or more). Results 204 patients had complete colonoscopy and enough data to be analyzed for the study. The Pearson correlation coefficient for the time between the last dose of NaP and colonoscopy was -0.450 (p=0.0001) showing an inverse correlation. The mean cleansing score (±SEM) of group 1 was 4.00±0.12, for group 2 it was 3.56±0.12, and for group 3 it was 2.64±0.14. There were statistically significant differences between all groups. Conclusion The cleansing result of NaP is inversely correlated with the time between last dose of NaP and colonoscopy. Colonoscopy should be preferably performed within 12 hours of taking the second dose of NaP.