The Decline of Sensory-Motility Coordination in Rectal Evacuation due to Pelvic Floor Dysfunction

Constipation, a common defecatory disorder, exhibits various symptoms and individual variability. Abnormalities in rectal sensation and/or motility are prevalent among patients. However, the mechanisms linking rectal sensation and motility, and their impact on rectal evacuation function, remain poorly understood.

Our study gathered data from 154 chronic constipation patients, including rectal sensation and motility, electromyography, motor evoked potentials, defecography, and balloon expulsion test. The aim was to investigate the association between rectal sensation and motility in the context of different symptom profiles and to identify potential influencing factors and to evaluate their effect on rectal evacuation.

Defecatory desire volume affects contrast evacuation (r = -0.181, p = 0.042). Hyposensitive patients show lower balloon expulsion rates, rectoanal gradient, and manometric defecation index than hypersensitive patients (p = 0.002, 0.007, and 0.041). Rectal sensation correlates with rectoanal gradient across all sensitivity levels (p < 0.05). Excessive electromyographic activity affects maximum tolerable volume in rectoanal gradient compared to normal (r = -0.551 vs. -0.434). Neurological conduction dysfunction weakens rectal sensation-motility coordination. Age and gender synergistically affect this coordination in normal rectal sensitivity (p < 0.05), while patients with abnormal rectal sensitivity are more sensitive to constipation severity (p < 0.05).

A decrease in rectal sensitivity may impair normal rectal evacuation, a process that may involve rectal motility changes mediated by rectal sensation. Excessive electromyographic activity and neurological conduction dysfunction may both contribute to the decreased coordination between rectal sensation and motility. Furthermore, the severity of the disease, age, and gender may all influence this association.