The motor physiology of the rectum has remained largely
obscure, especially concerning the mechanism of rectal
motility. In the current communication we tested the possibility
of characterizing the mechanism of rectal motility
during filling and evacuation through the study of the rectal
electric activity in 16 healthy volunteers (mean age 43.6 ±
10.8 years; II men). Two monopolar silver-silver chloride
electrodes were introduced per anum and fixed to the rectal
mucosa by suction. The rectum was distended in 10 ml increments
of water by means of a balloon-ended catheter inserted
into the rectum. The rectal pressure was measured by one
catheter placed above and a second one below the rectal
balloon, and the 2 catheters were connected to 2 strain gauge
pressure transducers. Regular triphasic slow waves or pacesetter
potentials (PPs) were recorded from the 2 electrodes at
rest. PPs were superimposed or followed randomly by action
potentials (APs). AN but not PPs were coupled with elevated
rectal pressure. Rectal distension with 10 ml of water caused
no significant changes of the rectal pressure or EMG activity.
Distension with a mean volume of 27.3 ± 4.7 ml effected
a significant increase (p < 0.05) of the rectal electromechanical
activity proximally to the balloon and a decrease distally
(p < 0.05) to it. With progressive increase of the rectal dise
tension, the electromechanical activity continued to increase (proximally and to decrease distally to the balloon, until, at
a mean distending volume of 76.3 ± 3.7 ml, the balloon was
'dispelled to the exterior. In conclusion, the identification of
the modality of rectal motility during defecation was feasible
by recording the rectal electromechanical activity. The
rectal contraction is suggested to occur in a 'mass squeeze
manner' which squeezes the rectal contents aborally into the anal canal. The recognition of the rectal motor modality
appears to be important for the understanding of rectal
motility disorders. However, further studies are required to
confirm these findings. |
