Effect of rectal distension on rectal electromechanical activity

Area of Science:

• Gastroenterology
• Physiology
• Colorectal Surgery

Background:

• The rectum exhibits electrical activity, including pacesetter potentials (PPs) and action potentials (APs), which influence rectal motility.
• Rectal motile activity is thought to be driven by electric waves affecting longitudinal muscle contraction and by circular muscle stretch from rectal distension.

Purpose of the Study:

• To investigate the impact of rectal overdistension on rectal electromechanical activity.
• To assess how stool accumulation in the rectum affects rectal motility.

Main Methods:

• Simultaneous recording of rectal electrical activity (PPs and APs) and intraluminal pressure in dogs under general anesthesia.
• Rectal distension was induced using a CO2-inflated balloon, with incremental inflation and simultaneous electromechanical recording.
• Measurements included pressure, frequency, amplitude, and conduction velocity of rectal electric waves.

Main Results:

• Rectal distension significantly increased rectal pressure and the frequency, amplitude, and conduction velocity of PPs and APs.
• These variables peaked just before balloon expulsion at 40 mL distension.
• At 50-60 mL overdistension, rectal electromechanical activity (PPs and APs) ceased, rectal pressure dropped to zero, and balloon expulsion failed.

Conclusions:

• Rectal overdistension (pathologic distension) can abolish rectal electromechanical activity.
• This loss of activity is likely due to overstretching of rectal musculature, leading to failed muscle contraction and rectal atony.
• These findings may explain the pathophysiology of rectal inertia and constipation.