Influence of continuous, isobaric rectal distention on smooth muscle tone and cardiovascular activation in healthy volunteers.

Interactions between visceral, intestinal stimulation and autonomic cardiovascular function have received increasing attention over the last years. The aim of the study was to investigate the effect of long-term continuous rectal distention on rectal tone and cardiovascular function at the threshold for first sensation of distention and moderate urge to defecate compared to a resting period without distention. Continuous isobaric rectal distention was performed in 13 healthy volunteers with a ten minute pressure tracking procedure at each subject's predetermined individual threshold for either moderate urge or first sensation, separated by a ten minute resting period. Rectal volume, heart rate, systolic and diastolic blood pressure were determined continuously. RESULTS: Rectal tone decreased significantly over time at the threshold for moderate urge and first sensation. Cardiovascular measures remained stable over the distention procedures, except for a significant increase in systolic blood pressure at the threshold for moderate urge. DISCUSSION: The previously reported rectal accommodation response to rectal distention was confirmed. The increase in systolic blood pressure is most likely mediated through sympathetic efferent pathways.