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At least 325 records · Page 18Linked to original sources
PubMed1996

Sigmoido-rectal junction reflex: role in the defecation mechanism.

The presence of a sphincter at the rectosigmoid junction (RSJ) is debated. This investigation studies the presence or absence of a sphincter and its possible role in sigmoid colon storage and rectal evacuation. Eighteen healthy volunteers (10 males, 8 females) with a mean age of 36.6 +/- 14.8 years (range 21-53) were studied. The pressure response of the sigmoid colon, RSJ, and rectum to sigmoid and rectal distension, respectively, was determined before and after anesthetizing either the sigmoid colon or the rectum. The RSJ length was evaluated by the station pull-through technique. Sigmoid distension with balloon volumes of up to 80.6 +/- 4.4 ml of H2O effected no sigmoid, RSJ or rectal pressure changes (P > 0.05). At a mean sigmoid distension of 88.6 +/- 4.1 ml of H2O, the sigmoid colon showed a significant pressure increase (P < 0.001), a RSJ pressure decrease (P < 0.05), and insignificant pressure changes in the rectum (P > 0.05); the balloon was dispelled into the rectum. Rectal distension of 94.6 +/- 5.8 ml of H2O produced rectal (P < 0.001) and RSJ (P < 0.05) pressure increases. Distension of the anesthetized sigmoid and rectum did not produce pressure changes in the RSJ (P > 0.05). This study demonstrated a high pressure zone at the RSJ of 3.8 +/- 0.7 cm in length. This suggests that the RSJ might act as a functional sphincter. It opens reflexly upon sigmoid contraction, by a reflex we call "rectosigmoid inhibitory reflex," and closes upon rectal contraction, a reflex we call "rectosigmoid excitatory reflex." The former allows the stored feces in the sigmoid colon to pass to the rectum, and the latter reflex prevents stool reflux to the sigmoid upon rectal contraction.

Administration, Topical↗
PubMed1998

A new concept of the anatomy of the anal sphincter mechanism and the physiology of defecation: mass contraction of the pelvic floor muscles.

We have previously demonstrated both anatomically and physiologically that the external anal (EAS) and urethral (EUS) sphincters and the bulbocavernosus muscle (BC) originate from the puborectalis muscle (PR). It is hypothesized that stimulation of any of these muscles would lead to contraction of all the others. Because the levator ani (pubococcygeus) muscle (LA) also has the same innervation as the above-mentioned muscles, it is further suggested that it, too, contracts reflexly upon stimulation of any of those muscles. The purpose of this study was to test this hypothesis. The study comprised 18 healthy volunteers (mean age 36.6 +/- 8.4 years; 10 men, 8 women). The EAS was stimulated and the response of the EUS, PR, LA and BC was determined. Each muscle was thereafter stimulated separately and the response of the other pelvic floor muscles registered. Stimulation of any of the pelvic floor muscles effected an increased EMG activity of the rest of the muscles. The muscle contraction was instantaneous with no latency in all the muscles except the LA EMG activity, which showed a mean latency of 21.3 +/- 6.6 ms. The pelvic floor muscles' response seems to be attributable to muscle stimulation both directly and indirectly through activation of pudendal nerve fibers in the muscles. The study demonstrated that the pelvic floor muscles behave as one muscle: they contract or relax en masse. This 'mass contraction' might explain some of the physiologic phenomena that occur during pelvic organ evacuation. However, besides this mass contraction, a voluntary 'selective' individual muscle activity exists by which each individual muscle acts independently of the others.

Action Potentials↗
PubMed1994

Ileal pouch pressures after defecation in continent and incontinent patients.

UNLABELLED: After ileal pouch-anal anastomosis, a pouch/anal canal pressure gradient is present such that mean pressures in the anal canal exceed pressures in the pouch facilitating fecal continence. Such a relationship was not present in incontinent patients. PURPOSE: Our aim was to evaluate characteristics of pouch pressures dynamically in continent and incontinent patients following ileal pouch-anal anastomosis (IPAA). METHODS: A multichannel microtransducer catheter was positioned in eight continent patients and nine incontinent patients after IPAA. Twenty-four-hour recordings of pouch pressures and large pressure wave contractions were recorded when patients were awake, asleep, and after evacuation. RESULTS: When patients were awake, pouch pressures were similar. However, nocturnal pouch pressures were higher in the incontinent group (P < 0.05). Large pressure wave amplitude was higher in incontinent patients when awake and asleep (P < 0.05). Moreover, pouch pressures failed to decline in the incontinent group after evacuation, unlike continent patients. CONCLUSION: Compared with continent patients, incontinent patients after IPAA had persistently high phasic and basal pouch pressures at night and following pouch evacuation.

Adult↗
PubMed1991

Are pelvic floor movements abnormal in disordered defecation?

Pelvic floor movements were assessed by videoproctography in 126 subjects: neuropathic fecal incontinence patients (n = 44), chronic constipation patients (n = 52), and controls (n = 30). A significantly lower pelvic floor position at rest and a more obtuse anorectal angle were found in incontinent patients than in controls (P less than 0.01). Constipated patients showed no significant difference from controls at rest. There was less pelvic floor movement during contraction in incontinent patients than in controls, indicating a flaccid, noncontractile pelvic floor in neuropathic incontinence. Movement during contraction in constipated subjects was also less than in controls. Changes in the pelvic floor position during straining were the same as in controls. These data indicate that the pelvic floor is flaccid and noncontractile in neuropathic fecal incontinence, which supports the concept of a progressive neuropathy involving the sacral outflow. Similar changes are not seen at rest in patients with constipation even though they have a long history of straining.

Adult↗