Rao S S, Welcher K
Department of Internal Medicine, University of Iowa College of Medicine, Iowa City, USA.
Am J Gastroenterol. 1996 May;91(5):890-7.
Rectal motor activity is incompletely understood. The aim of this study was to characterize the patterns of rectal motor activity and to examine their diurnal variation and their relationships to proximal colonic activity and to meals.
We performed a 30-h ambulatory motility study by recording pressure activity at multiple sites in the colon in 18 normal subjects.
During 288 h of recording, discrete bursts of tonic and phasic activity were seen in the rectum of all subjects at night and during the day lasting > or = 3 min, with a predominant frequency of 3 waves/min: periodic rectal motor activity (PRMA). Nocturnally, the number of cycles and the proportion of time occupied by this activity were greater (p < 0.001) and the inter-cycle interval was shorter (p < 0.008) compared with daytime, but the cycle duration was similar. Only 4 versus 5% (nocturnal vs daytime) of cycles propagated aborad, whereas 36 versus 14% (p < 0.01) propagated retrogradely, 16 versus 47% (p < 0.01) occurred simultaneously, and 44 versus 34% were confined to the rectum. There was considerable intra- and intersubject variability. PRMA was not related to meals or to anal motor activity, but 81% of nocturnal and 94% of daytime cycles occurred within 5 min of a motor event in the more proximal colon.
PRMA is a characteristic feature of the normal rectum and is more frequent at night. The temporal association with motor events in the proximal colon suggests that PRMA is triggered by the arrival of stool or gas in the rectum. Because most cycles are either segmental or are propagated retrogradely, PRMA may serve as an intrinsic braking mechanism that prevents untimely flow of colonic contents, particularly during sleep.
直肠运动活动尚未被完全理解。本研究的目的是描述直肠运动活动的模式，并研究其昼夜变化以及与近端结肠活动和进食的关系。
我们对18名正常受试者的结肠多个部位进行压力活动记录，开展了一项为期30小时的动态运动研究。
在288小时的记录过程中，所有受试者的直肠在夜间和白天均出现持续≥3分钟的离散性强直性和阶段性活动爆发，主要频率为每分钟3次波：周期性直肠运动活动（PRMA）。夜间，与白天相比，该活动的周期数和所占时间比例更大（p<0.001），周期间隔更短（p<0.008），但周期持续时间相似。只有4%与5%（夜间与白天）的周期向远端传播，而36%与14%（p<0.01）逆向传播，16%与47%（p<0.01）同时发生，44%与34%局限于直肠。个体内和个体间存在相当大的变异性。PRMA与进食或肛门运动活动无关，但81%的夜间周期和94%的白天周期发生在近端结肠运动事件的5分钟内。
PRMA是正常直肠的一个特征，夜间更为频繁。与近端结肠运动事件的时间关联表明，PRMA是由粪便或气体进入直肠触发的。由于大多数周期要么是节段性的，要么是逆向传播的，PRMA可能作为一种内在制动机制，防止结肠内容物过早流动，尤其是在睡眠期间。
