Effect of glycerin on colonic motility in children

Colonic manometry (CM) involves measurement of colonic neuromuscular activity and administration of a stimulant laxative, most commonly bisacodyl, which is part of the study protocol. Glycerin is another laxative used in the treatment of constipation. Our objective was to evaluate the effect of glycerin on colonic motility and compare the response to glycerin with each patient's response to bisacodyl.

We performed a retrospective review of all CM studies performed between May 2015 and May 2022. All studies with glycerin administration were included. Patient demographics, medical and surgical history, and results of each CM, including name, number, and dose of stimulant laxatives administered, colonic motor response after each stimulant, and final interpretation, were recorded.

We included 131 CM studies in 125 patients (53% female, median age at CM 10 years, interquartile range 7-14 years). Compared to bisacodyl, glycerin more commonly triggered fully propagated high-amplitude propagating contractions (HAPCs; 35% vs. 13%, p < 0.001) and led to a greater extent of propagation (propagation to sigmoid vs. to descending colon, p < 0.001). In 36% of studies, glycerin led to an improved response (stimulation of HAPCs when they were absent after bisacodyl, or HAPCs propagating through a greater extent of colon) compared to bisacodyl. In studies with an improved response, the median dose of glycerin in mL/kg was not significantly different compared to studies with the same/worse response.

Glycerin can trigger HAPCs in patients in whom bisacodyl was not able to do so. Incorporation of glycerin into standard CM protocols should be considered.