Ssc. Rao et K. Welcher, PERIODIC RECTAL MOTOR-ACTIVITY - THE INTRINSIC COLONIC GATEKEEPER, The American journal of gastroenterology, 91(5), 1996, pp. 890-897
Background: Rectal motor activity is incompletely understood, The aim
of this study was to characterize the patterns of rectal motor activit
y and to examine their diurnal variation and their relationships to pr
oximal colonic activity and to meals, Methods: We performed a 30-h amb
ulatory motility study by recording pressure activity at multiple site
s in the colon in 18 normal subjects, Results: During 288 h of recordi
ng, discrete bursts of tonic and phasic activity were seen in the rect
um of all subjects at night and during the day lasting greater than or
equal to 3 min, with a predominant frequency of 3 waves/min: periodic
rectal motor activity (PRMA). Nocturnally, the number of cycles and t
he proportion of time occupied by this activity were greater (p < 0.00
1) and the inter-cycle interval was shorter (p < 0.008) compared with
daytime, but the cycle duration was similar, Only 4 versus 5% (nocturn
al vs daytime) of cycles propagated aborad, whereas 36 versus 14% (p <
0.01) propagated retrogradely, 16 versus 47% (p < 0.01) occurred simu
ltaneously, and 44 versus 34% were confined to the rectum, There was c
onsiderable intra- and intersubject variability, PRMA was not related
to meals or to anal motor activity, but 81% of nocturnal and 94% of da
ytime cycles occurred within 5 min of a motor event in the more proxim
al colon, Conclusions: PRMA is a characteristic feature of the normal
rectum and is more frequent at night, The temporal association with mo
tor events in the proximal colon suggests that PRMA is triggered by th
e arrival of stool or gas in the rectum, Because most cycles are eithe
r segmental or are propagated retrogradely, PRMA may serve as an intri
nsic braking mechanism that prevents untimely flow of colonic contents
, particularly during sleep.