Physiology of rectal sensations: a mathematic approach

Area of Science:

• Gastroenterology
• Physiology
• Computational Modeling

Background:

• Rectal sensations are traditionally linked to pelvic floor mechanoreceptors.
• Emerging evidence suggests rectal wall mechanoreceptors play a key role.
• Understanding the physiology of rectal sensations is crucial for diagnosing defecation disorders.

Purpose of the Study:

• To investigate the physiological basis of four rectal sensations using a dynamic mathematical model.
• To differentiate between rectal wall and anal canal contributions to rectal sensations.
• To determine the clinical relevance of commonly evaluated rectal sensations.

Main Methods:

• A dynamic mathematical model of the rectum was developed.
• The model analyzed smooth muscle activity in relation to rectal sensations in 15 healthy volunteers.
• Strain levels of smooth muscle components were correlated with sensations of first sensation (FS), constant sensation (CS), urge to defecate (UD), and maximum tolerated threshold (MTT).

Main Results:

• Longitudinal and circular smooth muscle relaxation were identified as rate detection and signaling mechanisms, respectively.
• Circular muscle relaxation triggered CS, UD, and MTT.
• FS was identified as an anal canal sensation linked to the rectoanal inhibitory reflex, while MTT appeared to be a protective mechanism.

Conclusions:

• Clinical evaluation of rectal sensations should focus on CS and UD.
• MTT provides no additional information beyond pain and is not a true rectal sensation.
• FS is not a rectal phenomenon and should not be considered in rectal sensation evaluation.