We evaluated whether colonic transit time (CTT) can predict the degree of bowel preparation in patients with chronic constipation undergoing scheduled colonoscopy in order to assist in the development of better bowel preparation strategies for these patients.

We analyzed the records of 160 patients with chronic constipation from March 2007 to November 2012. We enrolled patients who had undergone a CTT test followed by colonoscopy. We defined patients with a CTT ≥30 hours as the slow transit time (STT) group, and patients with a CTT <30 hours as the normal transit time (NTT) group. Boston Bowel Preparation Scale (BBPS) scores were compared between the STT and NTT groups.

Of 160 patients with chronic constipation, 82 (51%) were included in the STT group and 78 (49%) were included in the NTT group. Patients with a BBPS score of <6 were more prevalent in the STT group than in the NTT group (31.7% vs. 10.3%, P =0.001). Multivariate analysis showed that slow CTT was an independent predictor of inadequate bowel preparation (odds ratio, 0.261; 95% confidence interval, 0.107-0.634; P =0.003). The best CTT cut-off value for predicting inadequate bowel preparation in patients with chronic constipation was 37 hours, as determined by receiver operator characteristic (ROC) curve analysis (area under the ROC curve: 0.676, specificity: 0.735, sensitivity: 0.643).

Patients with chronic constipation and a CTT >30 hours were at risk for inadequate bowel preparation. CTT measured prior to colonoscopy could be useful for developing individualized strategies for bowel preparation in patients with slow CTT, as these patients are likely to have inadequate bowel preparation.