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| 번호 | 제목 | 등록일 | 조회수 |
|---|---|---|---|
| 37 | Rectal Sensory Perception in Females with Obstructed Defecation [2001년 9월 DCR] | 2011-11-17 | 3413 |
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M. J. Gosselink, M.D., Ph.D., W. R. Schouten, M.D., Ph.D.
From the Colorectal Research Group, Department of Surgery, Erasmus Medical Centre Rotterdam,
The Netherlands PURPOSE: Parasympathetic afferent nerves are thought to mediate rectal filling sensations. The role of sympathetic afferent nerves in the mediation of these sensations is unclear. Sympathetic nerves have been reported to mediate nonspecific sensations in the pelvis or lower abdomen in patients with blocked parasympathetic afferent supply. It has been reported that the parasympathetic afferent nerves are stimulated by both slow ramp (cumulative) and fast phasic (intermittent) distention of the rectum, whereas the sympathetic afferent nerves are only stimulated by fast phasic distention. Therefore, it might be useful to use the two distention protocols to differentiate between a parasympathetic and sympathetic afferent deficit.
METHODS: Sixty control subjects (9 males; median age, 48 (range, 20-70) years) and 100 female patients (median age, 50 (range, t8-75) years) with obstructed defecation entered the study. Rectal sensory perception was assessed with an "infinitely" compliant polyethylene bag and a computer-controlled airinjection system. This bag was inserted into the rectum and inflated with air to selected pressure levels according to two different distention protocols (fast phasic and slow ramp). The distending pressures needed to evoke rectal filling sensations, first sensation of content in the rectum, and earliest urge to defecate were noted, as was the maximum tolerable volume.
RESULTS: In all control subjects, rectal filling sensations could be evoked. Twenty-one patients (21
percent) experienced no sensation at all in the pressure range between 0 and 65 mmHg during either slow ramp or fast phasic distention. The pressure thresholds for first sensation, earliest urge to defecate, and maximum tolerable volume were significantly higher in patients with obstructed defecation (P < 0.001). In each subject, the pressure thresholds for first sensation, earliest urge to defecate, and maxhnum tolerable volume were always the same, regardless of the type of distention. CONCLUSION: Rectal sensory perception is blunted or absent in the majority of patients with obstructed defecation. The observation that this abnormality can be detected by both distention protocols
suggests that the parasympathetic afferent nerves are deticient Because none of the patients experienced a nonspecific sensation in the pelvis or lower abdomma during fast phasic distention, it might be suggested that the sympathetic afferents are also deficient. This finding implies that it is not worthwhile to use different distention protocols in patients with obstructed defecation. For almost three decades, paradoxical contraction of the pelvic floor has been cited as the principal
cause of obstructed defecation. However, the clinical relevance of this pelvic floor dysfunction has been questioned. Normal rectal evacuation requires adequate intrarectal pressure, which can be raised by increasing intrapelvic pressure, achieved by voluntary contraction of the diaphragm and abdominal wall muscles. Furthermore, increase of rectal tone proximal to the fecal mass and normal sensory perception also contribute to normal rectal evacuation. Recently, it has been shown that the rectum generates an expelling force during an evoked call to stool. In patients with obstructed defecation, this expelling force is impaired. Many patients with obstructed defecation report that their feelings of a call to stool are blunted or absent. Balloon distention of the rectum is a widely used, simple method to measure rectal sensory perception. It has been shown that the perception of a balloon distending the rectal wall is reduced in patients with constipation. In these studies, balloons of different materials, shapes and sizes were used. Some workers inflated the stimulating balloon with air, whereas others used water. Some investigators used phasic distention, characterized by periods of balloon inflation separated by periods of balloon deflation. Other workers used ramp distention or staircase distention, both characterized by cumulative stimuli. It has been reported that latex balloons supply a compliance term of their own. This implies that these balloons continue to increase in size when high pressures are applied, i.e., they still expand within a rigid tube, thereby not reflecting their low compliance. This is in contrast with polyethylene bags. Recently, it has been described that a polyethylene bag is the optimum device to use in distention protocols, because these bags have an "infinitely" high compliance. The pressure in these bags truly represents the pressure exerted on the rectal wall. Sensory signals from the rectum are transported by both parasympathetic and sympathetic afferent nerves. The parasympathetic afferent nerves are thought to mediate rectal filling sensations. Although the exact role of the sympathetic afferent nerves is not clear, there is growing evidence that these nerves mediate feelings of abdominal pain in patients with irritable bowel syndrome.
It has been reported that parasympathetic afferent nerves are stimulated by both slow ramp (cumulative)
and fast phasic (intermittent) distention of the rectum. The sympathetic afferent nerves are only stimulated by fast phasic (intermittent) distention. In patients with a complete thoracic spinal cord lesion below T7, the parasympathetic pathway is blocked completely, whereas the sympathetic pathway through the splanchnic thoracolumbar nerves is partially intact. These patients experience no rectal filling sensations during either slow ramp or fast phasic distention. However, during fast phasic distention, the majority of patients report a nonspecific sensation in the pelvis or lower abdomen characterized as "fullness," "stool," or "discomfort. This sensation is supposed to be mediated by the sympathetic afferent nerves. Patients with a high cervical lesion, in whom the parasympathetic and sympathetic pathways are both blocked totally, perceived no sensation during balloon distention. On the basis of the assumption that different distention protocols stimulate distinct afferent nerve pathways, it might be possible to use slow ramp and fast phasic distention protocols to differentiate between a parasympathetic or sympathetic afferent deficit. DISCUSSION
Normal rectal evacuation requires adequate intrarectal pressure, which can be raised by increasing
intrapelvic pressure, achieved by voluntary contraction of the diaphragm and abdominal wall muscles. Furthermore, increase of rectal tone proximal to the fecal mass, as well as normal sensory perception, also contributes to normal rectal evacuation. Initially, it was thought that rectal sensory perception depends on receptors located in the rectal wall, as well as in the pelvic floor. Recent studies have cast doubt on the role of the pelvic floor in rectal sensory perception. Sensory signals from the rectum, are transported by both parasympathetic and sympathetic afferent nerves. The parasympathetic afferent nerves run from the rectum through branches that are situated on each side of the rectum and around the cervix uteri. They also run on both lateral vaginal surfaces and are applied to the lateral surfaces and base of the bladder. A11 these parasympathetic afferent nerves join in the inferior hypogastric (pelvic) plexus and run to the second and third sacral segments of the spinal cord. The parasympathetic afferent nerves mediate rectal filling sensations. Goligher and Hughes investigated rectal sensory perception in six patients before and after induction of low spinal anesthesia. Owing to this anesthesia, all parasympathetic afferent nerves were blocked. None of the patients
experienced any sensation during continuous (ramp) distention of the rectum with a balloon. Gunterberg et al.examined anorectal functt'on in four patients with unilateral and three with bilateral loss of sacral nerves after radical tumor excision. In patients with unilateral loss of the sacral nerves, no significant impairment of anorectal function was noted. However, in patients with bilateral loss of sacral nerves, there was a serious impairment of rectal filling sensations. The same observation was made by Nakahara et al. The sympathetic afferent nerves run from the rectum together with the parasympathetic afferent nerve
branches. They cross the inferior hypogastric plexus and run through the superior hypogastric plexus to the spinal cord between the third thoracic and third lumbar segments. Some sympathetic branches run directly to the sacral portion of the sympathetic trunk and run upward via the thoracolumbar sympathetic trunk to the third thoracic and third lumbar segments. The physiologic role of the sympathetic afferents is poorly understood. In the rat, destruction of these
nerves has no effect on defecation pattern. In the 1950s, extensive sympathectomy was frequently used to treat essential hypertension. During this procedure, sympathetic outflow from. T3 to L3 on both sides of the spine was divided. This operation also deprived the entire colon and rectum of tJmir sympathetic afferent nerves. After this procedure, patients were still able to perceive normal rectal filling sensations after ramp (continuous) distention. The sympathetic afferent nerves have been reported to mediate nonspecific sensations in the pelvis or lower abdomen in patients with thoracic spinal cord lesions, in whom the parasympathetic afferent nerves are completely blocked but the sympathetic afferent nerves are partially intact. The pathophysiology of obstructed defecation is still incompletely understood. Diminished rectal perception of balloon distention in patients with constipation has been reported previously. The cause of
this alteration in rectal sensory perception is not clear. Increased rectal compliance might be a contributing factor, because it would require larger volumes to reach an adequate stimulating pressure on the rectal wall. However, De Medici et al. reported that rectal
compliance was normal in patients with constipation, in whom rectal sensory perception was impaired. This finding is in accordance with our own observations. It has been suggested that impaired rectal sensory perception is due to a derangement of parasympathetic afferent nerves. It is well known that in some females, obstructed defecation starts, or deteriorates, after pelvic surgery. Patients who have undergone rectopexy frequently experience diminished rectal sensory perception. This has been attributed to the division of the lateral ligaments, which contain branches of both the parasympathetic and sympathetic afferent nerves. After hysterectomy, changes in bowel function have been reported by 43 percent of females. The parasympathetic afferent nerves run from the rectum through branches that are situated on each side of the rectum, around the cervix uteri, and on both lateral vaginal surfaces. This extensive network of nerve fibers is difficult to spare during hysterectomy and dissection of the rectovaginal septum. Gumari et al. showed that constipation occurred more frequently the more radical the hysterectomy. Varma studied rectal function in 14 females with intractable constipation after hysterectomy. Those patients had significantly decreased rectal sensory perception to ramp distention. However, no prospective studies regarding the relationship between onset of obstructed defecation and hysterectomy have been performed. It has also been suggested that a central neurogenic deficit contributes to obstructed defecation. It is most likely that this central deficit is situated in the anterior side of the pons cerebri, where the coordinating center of micturition is also located. Fukuda et at. reported that neurons in the reticular area of the pons respond to stimulation of parasympathetic afferent nerves that run from the rectum. Moreover, patients with a vascular lesion of the pons did not have any sensation during balloon distention.
The parasympathetic afferent nerves can be stimulated by both slow ramp and fast phasic distention of
the rectum. The sympathetic afferent nerves can only be stimulated by fast phasic distention. This impties that it might be useful to use these two distention protocols to differentiate between a parasympathetic or sympathetic afferent deficit. If the parasympathetic afferent nerves are intact, normal rectal filling sensations will be experienced. In
case of a parasympathetic deficit and normal functioning of sympathetic afferents, no rectal filling sensations will be experienced, except for a nonspecific sensation in the pelvis or lower abdomen at fast phasic distention. If both afferent pathways are deficient, no sensation will be experienced. In control subjects, as well as in females with obstructed defecation, no difference was found in perception of slow ramp and fast phasic distention. The same observation was made by Hammer et al.,
who reported that different distention protocols and different rates of inflation had little effect on rectal perception. However, Sun et al. observed a higher perception threshold for fast distention rates than for slow rates in control subjects. Furthermore, they observed that during phasic distention, rectal volumes required to elicit filling sensations were lower than during ramp distention. Plourde et al.also found that
sensory thresholds increased with increasing rate of distention, whereas they observed that rectal sensory perceptions for ramp and phasic distensions were similar. We have no explanation for the fact that our findings are not in accordance with those reported by Sun et al. and Plourde et al. Twenty-one patients did not perceive any rectal filing sensation at all during either slow ramp or fast
phasic distention. This observation suggests a parasympathetic deficit in these patients. If the sympathetic afferent nerves were intact, they would be able to mediate nonspecific sensations in the pelvis or lower abdomen during fast phasic distention. During fast phasic distention, however, none of the females experienced such a sensation. Assuming that the hypothesis of discrimination between different neurogenic pathways by different distention protocols is true, this suggests that the sympathetic afferent nerves are deficient as well. In the majority of the remaining patients, rectal filling sensations were blunted during both slow ramp and fast phasic distention. None of these patients perceived a nonspecific sensation during fast phasic distention. It seems likely that in these patients, both afferent pathways are deficient. Because symptoms of obstructed defecation began shortly after pelvic surgery in 49 of the patients, we assume that this deficit is located at a peripheral level and not at a central level. |
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