Figure 4. Conceptual framework of interactions between fecal and colonic mucosal microbiota, colonic transit, breath methane excretion, and constipation.

To emphasize, the lines denote associations, not causality a solid line represents an association that remained statistically significant in the multivariate analyses; the dotted line represents an association that was only univariately statistically significant (Table 2); the asterisk denotes relationships that are supported by previous literature. While the mucosal microbiota is associated with constipation, independent of colonic transit, the fecal microbiota is associated with colonic transit and breath methane production.