To evaluate the correlation between stool characteristics (consistency and frequency) and gut transit time in children and to determine whether the Bristol Stool Form Scale is a reliable method of assessing intestinal transit rate in children.

From March 2011 to March 2012, 44 children (25 boys and 19 girls, mean age 7.8 years) with a diagnosis of functional constipation and 36 healthy, nonconstipated children (17 boys and 19 girls, mean age 7.6 years) were enrolled. All participants maintained a 1-week stool diary, recording the time and date of every bowel movement and stool form, and then completed a validated questionnaire on functional constipation according to Rome III criteria. Whole gut transit time (WGTT) was then assessed using the radiopaque markers test.

There was a significant correlation between stool form and WGTT in both constipated and nonconstipated children (correlation coefficient −0.84, P < .001). By contrast, there was no correlation between either stool frequency and WGTT or stool frequency and stool form. Multivariate logistic regression analysis, using WGTT as a dependent variable, showed that the sole variable significantly associated with WGTT was stool form (regression coefficient 2.9, OR 18.4, 95% CI 5.4-62.5, P < .001).

In this prospective, observational, case-control study, we show that stool form, as measured by the Bristol Stool Form Scale, rather than stool frequency, correlates with WGTT in both constipated and nonconstipated children.