Human anal motility while fasting, after feeding, and during sleep

Area of Science:

• Gastroenterology
• Physiology
• Anorectal Function

Background:

• The human anal sphincter plays a crucial role in maintaining fecal continence.
• Understanding its dynamic pressure variations under different physiological states is essential for diagnosing anorectal disorders.

Purpose of the Study:

• To investigate the dynamic response of the human anal sphincter pressure to varying physiological conditions.
• To compare anal sphincter pressure patterns during fasting, feeding, and sleep.

Main Methods:

• Intraluminal anal canal pressure was measured in 19 healthy subjects using a perfused sleeve sensor.
• Measurements were taken during daytime fasting, daytime post-feeding, and nighttime sleep.

Main Results:

• Mean anal canal pressure remained consistent across fasting, feeding, and sleep states.
• Significant minute-to-minute pressure variations and large phasic waves (increases/decreases >20 mm Hg) were observed in all states.
• These variations and large phasic waves were more pronounced during the awake fed state than during sleep (P < 0.05).
• Small phasic changes (anal slow waves) occurred at a similar frequency (~17 waves/min) across all conditions.

Conclusions:

• The anal sphincter provides a continuous pressure barrier against rectal outflow, both during wakefulness and sleep.
• While overall pressure is maintained, dynamic pressure variations and phasic waves are characteristic of anal sphincter function.
• These dynamic activities are reduced during sleep, suggesting a role for physiological state in modulating anal sphincter function.