Rectoanal reflex in healthy subject

The present work was performed in order to examine the rectoanal reflex in healthy subject. Our findings suggest that the fecal continence is sustained by both the anal sphincters. The maximal anal pressure at rest is governed by activity of the internal sphincter while the external anal sphincter promptly contracts when the rectum is distended.     

A new possibility for repairing the anal dysfunction by promoting regeneration of the reflex pathways in the enteric nervous system

Moderate rectal distension elicits recto-rectal reflex contractions and simultaneous recto-internal anal sphincter reflex relaxations that together comprise the defecation reflex. Both reflexes are controlled by 1) pelvic nerves, 2) lumbar colonic nerves, and 3) enteric nervous system. The aim of the present study was to explore a novel approach to repairing the defecation reflex dysfunction by using the plasticity of enteric nervous pathways. Experiments were performed in anesthetized guinea pigs with ethyl carbamate. The rectum 30 mm oral from the anal verge was transected without damage to extrinsic nerves, and subsequent end-to-end one-layer anastomosis was performed. Recovery of the defecation reflex and associated reflex pathways were evaluated. Eight weeks after sectioning of intrinsic reflex nerve pathways in the rectum, the defecation reflex recovered to the control level, accompanied with regeneration of reflex pathways. The 5-HT(4)-receptor agonist mosapride (0.5 and 1.0 mg/kg) significantly (P < 0.01) enhanced the recovered defecation reflex 8 wk after surgery. Two weeks after local treatment with brain-derived neurotrophic factor (BDNF: 10(-6) g/ml) at the rectal anastomotic site, the recto-internal anal sphincter reflex relaxations recovered and some bundles of fine nerve fibers were shown to interconnect the oral and anal ends of the myenteric plexus. These results suggested a possibility for repairing the anal dysfunction by promoting regeneration of the reflex pathways in the enteric nervous system with local application of BDNF.     

Dilatation and closing anal reflexes. Description and clinical significance of new reflexes: preliminary report.

The present communication describes new reflexes which are called 'dilatation and closing anal reflexes', and discusses their clinical significance. The study comprised 21 healthy volunteers and 15 incontinent patients (7 with partial fecal incontinence and 8 with urinary stress incontinence). The technique comprised the introduction into the rectal neck of a balloon-tipped catheter. The balloon was inflated with air in increments of 10 ml up to 50 ml, and the EMG response of the external and urethral sphincters to balloon inflation and deflation was recorded. A new device called 'switch inflation' apparatus was used to inflate the balloon simultaneously with switching of the EMG apparatus. Rapid rectal neck inflation and deflation evoked external anal and urethral sphincter contraction. Slow and gradual inflation or deflation did not initiate the response. The anesthetized external anal sphincter did not respond to the stimulus, while the saline-infiltrated sphincter responded. The latency of the reflexes was recorded. In fecal incontinent patients, the external anal sphincter, on rapid rectal neck inflation or deflation, showed lower EMG activity and longer latency than in normal volunteers; the external urethral sphincter responded as in normal volunteers. In urinary stress incontinent patients, the external anal sphincter responded normally for both rectal neck inflation and deflation. The external urethral sphincter showed lower EMG activity and prolonged latency than normal on rectal neck inflation; it did not respond to deflation. The dilatation and closing reflexes seem to play a role in fecal and urinary continence as well as in fecal sampling. Detectable changes in latency or amplitude of the evoked response indicate a defect in the reflex pathway.(ABSTRACT TRUNCATED AT 250 WORDS)     

Altered temporal characteristics of the rectoanal inhibitory reflex in patients with abdominal distension

The rectoanal inhibitory reflex (RAIR) is important in gas and stool evacuation. We examined RAIR features in patients with chronic constipation who exhibited bloating with and without abdominal distension, to determine whether alterations in RAIR may be a factor in the pathogenesis of abdominal distension. Seventy-five female patients with chronic constipation with or without abdominal distension were included in the study. The presence or absence of abdominal distension was assessed according to the Rome II questionnaire. All patients underwent both RAIR and rectal sensitivity testing, and specific RAIR parameters were analyzed. Patients were divided into two groups: abdominal bloating with distension (D, n = 55) and abdominal bloating without distension (ND, n = 20). D had a longer time to the onset of anal sphincter inhibition (latency of inhibition) (P = 0.03) compared with ND. In logistic regression analysis, a combination of age, latency of inhibition and the time measured from onset of inhibition to the point of maximum inhibition predicted abdominal distension (P = 0.002). There were no differences between groups for the time from point of maximum inhibition to recovery and for the percentage of internal anal sphincter relaxation. This is the first study to examine the role of RAIR in patients with abdominal distension. Female patients with constipation and abdominal distension exhibited differences in the temporal characteristics of, but not in the degree of, anal sphincter relaxation compared with patients without distension. Since this study was uncontrolled, further studies are necessary to determine the contribution of altered anorectal reflexes to abdominal distension.     

Anatomy of the external anal sphincter in man

The anatomy of the external anal sphincter was studied in 20 adult human cadavers of both sexes by dissection and histological examination. The external anal sphincter is not naturally divided into layers or laminae. The lowermost muscle bundles differ from the main part in being completely surrounded by thick fibrous tissue septa derived form the longitudinal anal coat. The perineal branch of S4 supplies the posterior third, the inferior haemorrhoidal nerves supply the anterior two thirds. All fibres of the sphincter retain their skeletal attachment to the anococcygeal ligament to the coccyx. Some fibres cross the median plane to be continuous with the transversus perinei of the opposite side. A cleft was displayed separating the lower border of the levator ani muscle from the upper border of the external anal sphincter. The muscle bundles of the sphincter are arranged circumferentially in one continuous circle and not in loops. Fibres from the anterior border of the levator ani muscle extend to cover and blend with the outer surface of the external sphincter in their way to the anococcygeal ligament.     

Straining urethral reflex: description of a reflex and its clinical significance. Preliminary report

The present communication describes a reflex, which I call 'straining urethral reflex', and discusses its clinical significance. The study was performed on 17 healthy volunteers with a mean age of 39.6 years. The intrarectal pressure (representative of the intra-abdominal pressure) was measured by means of a balloon-tipped catheter introduced into the rectum and connected to a pressure transducer. A concentric needle electrode was introduced into the external urethral sphincter. The subject was asked to strain, and the urethral sphincter electromyographic activity and the intrarectal pressure were recorded. Two types of straining were investigated: sudden and slow. The procedure was repeated in 10 subjects after urethral sphincter infiltration with xylocaine or saline. On sudden straining, the external urethral sphincter contracted. The anesthetized sphincter did not respond, while the saline-infiltrated sphincter responded to sudden straining. Slow sustained straining did not evoke the reflex response. The latency of the reflex was calculated. The external urethral sphincter contraction on sudden straining guards against the involuntary opening of the vesical neck and urinary leak under stress conditions of a sudden increase in the intra-abdominal pressure. The reflex may prove significant in the diagnosis of micturition control disorders. It can thus be included as an investigative tool in urologic practice.     

Mesenchymal stem cells can improve anal pressures after anal sphincter injury

Objective.Fecal incontinence reduces the quality of life of many women but has no long-term cure. Research on mesenchymal stem cell (MSC)-based therapies has shown promising results. The primary aim of this study was to evaluate functional recovery after treatment with MSCs in two animal models of anal sphincter injury.Methods.Seventy virgin female rats received a sphincterotomy (SP) to model episiotomy, a pudendal nerve crush (PNC) to model the nerve injuries of childbirth, a sham SP, or a sham PNC. Anal sphincter pressures and electromyography (EMG) were recorded after injury but before treatment and 10 days after injury. Twenty-four hours after injury, each animal received either 0.2 ml saline or 2 million MSCs labelled with green fluorescing protein (GFP) suspended in 0.2 ml saline, either intravenously (IV) into the tail vein or intramuscularly (IM) into the anal sphincter.Results.MSCs delivered IV after SP resulted in a significant increase in resting anal sphincter pressure and peak pressure, as well as anal sphincter EMG amplitude and frequency 10 days after injury. MSCs delivered IM after SP resulted in a significant increase in resting anal sphincter pressure and anal sphincter EMG frequency but not amplitude. There was no improvement in anal sphincter pressure or EMG with in animals receiving MSCs after PNC. GFP-labelled cells were not found near the external anal sphincter in MSC-treated animals after SP.Conclusion.MSC treatment resulted in significant improvement in anal pressures after SP but not after PNC, suggesting that MSCs could be utilized to facilitate recovery after anal sphincter injury.     

In vitro relaxation of rabbit and human internal anal sphincter by rutaecarpine, an alkaloid isolated from Evodia rutaecarpa

Rutaecarpine, a compound extracted from the Chinese medicinal herb Evodia rutaecarpa, has been shown to possess relaxing action on vascular smooth muscle from rat thoracic aorta. The internal anal sphincter is a specialized smooth muscle regulating important anorectal physiology. To investigate the effect and underlying mechanisms of rutaecarpine on internal anal sphincter, muscle strips from rabbit internal anal sphincter were used. The results showed that rutaecarpine (1 x 10(-10) M to 1 x 10(-4) M) produced a concentration-dependent muscular relaxation effect in our preparations, which were precontracted with acetylcholine. This muscular relaxation effect was not affected by treatment with L-N(G)-nitro-arginine methyl ester (a nitric oxide synthase inhibitor), methylene blue (a guanylate cyclase inhibitor), N-ethylmaleimide (an adenylate cyclase inhibitor), or by removal of the mucosa and submucosa tissue. Pretreatment with nifedipine (a calcium channel blocker) or extracellular Ca+2 removal by ethylenediaminetetraacetic acid (EDTA) greatly attenuated the relaxation effect, suggesting that calcium ion might be involved. In experiments using strips from human internal anal sphincter, an even more prominent relaxation effect was shown. It is thus concluded that rutaecarpine caused relaxation on internal anal sphincter from rabbits and human subjects. The relaxation action was not related to NO-cGMP pathway, instead calcium ion might play an important role and shed insight into clinical implications for those anorectal disorders with hyperactive anal tone.     

Integrative control of rectoanal reflex in guinea pigs through lumbar colonic nerves

The aim of the present study was to analyze the neuromodulation of rectoanal reflex activity by lumbar sympathetic nerves in guinea pigs. The mechanical activities of the rectum were recorded with a balloon connected to a pressure transducer, and those of the internal anal sphincter (IAS) were recorded with a custom-made strain gauge force transducer. Gradual and sustained rectal distension evoked the rectoanal reflex, causing cholinergic contractions of the rectum and synchronous nitrergic relaxations of the IAS. Section of the lumbar colonic nerves enhanced both rectal contractions and IAS relaxations. Section of the 13th thoracic cord abolished both rectal contractions and IAS relaxations, but section of the lumbar colonic nerves restored them. Lumbar sympathectomy and pithing sacral cords greatly diminished these rectal contractions and IAS relaxations, but the intrinsic reflex component remained. NG-nitro-L-arginine methyl ester enhanced the intrinsic reflex-mediated contraction of the rectum and abolished reflex-mediated relaxation of the IAS and converted into cholinergic contractions. The present results indicate that the extrinsic lumbar inhibitory outflow causes marked inhibition of the rectoanal reflex via the lumbar colonic nerves.     

Anal sphincteric neurogenic injury in asymptomatic nulliparous women and fecal incontinence

While anal sphincter neurogenic injury documented by needle electromyography (EMG) has been implicated to cause fecal incontinence (FI), most studies have been uncontrolled. Normal values and the effects of age on anal sphincter motor unit potentials (MUP) are ill defined. The functional significance of anal sphincter neurogenic injury in FI is unclear. Anal pressures and EMG were assessed in 20 asymptomatic nulliparous women (age, 38 ± 5 yr; mean ± SE) and 20 women with FI (54 ± 3 yr). A computerized program quantified MUP duration and phases. These parameters and MUP recruitment were also semiquantitatively assessed by experienced electromyographers in real time. Increasing age was associated with longer and more polyphasic MUP in nulliparous women by quantitative analysis. A higher proportion of FI patients had prolonged (1 control, 7 patients, P = 0.04) and polyphasic MUP (2 controls, 9 patients, P = 0.03) at rest but not during squeeze. Semiquantitative analyses identified neurogenic or muscle injury in the anal sphincter (11 patients) and other lumbosacral muscles (4 patients). There was substantial agreement between quantitative and semiquantitative analyses (κ statistic 0.63 ± 95% CI: 0.32-0.96). Anal resting and squeeze pressures were lower (P ≤ 0.01) in FI than controls. Anal sphincter neurogenic or muscle injury assessed by needle EMG was associated (P = 0.01) with weaker squeeze pressures (83 ± 10 mmHg vs. 154 ± 30 mmHg) and explained 19% (P = 0.01) of the variation in squeeze pressure. Anal sphincter MUP are longer and more polyphasic in older than younger nulliparous women. Women with FI have more severe neurogenic or muscle anal sphincter injury, which is associated with lower squeeze pressures.     

A 5-HT4 agonist, mosapride, enhances intrinsic rectorectal and rectoanal reflexes after removal of extrinsic nerves in guinea pigs

Distension-evoked reflex of rectorectal (R-R) contractions and rectointernal anal sphincter (R-IAS) relaxations can be generated in guinea pigs through an extrinsic sacral excitatory neural pathway (pelvic nerves) as well as intrinsic cholinergic excitatory and nitrergic inhibitory pathways. The aim of the present study was to create intrinsic R-R and R-IAS reflex models by pithing (destruction of the lumbar and sacral cords; PITH) and to evaluate whether the prokinetic benzamide mosapride, a 5-HT(4) receptor agonist, enhances these reflexes. The mechanical activities of the R-R and R-IAS were recorded in the anesthetized guinea pig on days 2-9 after PITH. Although the basal rectal pressure at distension after PITH was significantly lower than control, the reflex indexes of R-R contractions and synchronous R-IAS relaxations were unchanged between days 4 and 9 after PITH. The frequency of spontaneous rectal and IAS motility were also unchanged. Immunohistochemical studies revealed that the distribution of myenteric and intramuscular interstitial cells of Cajal (ICC) were not altered after PITH. Mosapride (0.1-1.0 mg/kg iv) dose-dependently increased both intrinsic R-R (maximum: 1.82) and R-IAS reflex indexes (maximum: 2.76) from control (1.0) 6-9 days after PITH. The 5-HT(4) receptor antagonist, GR-113808 (1.0 mg/kg iv) decreased the R-R and R-IAS reflex indexes by approximately 50% and antagonized the effect of mosapride (1.0 mg/kg iv). The present results indicate that mosapride moderately enhanced intrinsic R-R and R-IAS reflexes functionally compensated after deprivation of extrinsic nerves, mediated through endogenously active intrinsic 5-HT(4) receptors.     

Function of the anal sphincters following pull-through operations without anal eversion

It has been investigated the function of the anal sphincters following Bacon type pull-through operation. Our data have shown a significant decrease of the anal resting pressure after pull-through excision signifying an impairment in the internal sphincter function. But the tonic external sphincter contraction induced by stimulation can maintain continence.     

A new concept of the anatomy of the anal sphincter mechanism and the physiology of defecation. The involuntary action of the external anal sphincter: histologic study.

The histologic changes in the external anal sphincter after internal anal sphincter excision were studied in 20 dogs. An external sphincter biopsy was taken before internal sphincterectomy and 2 weeks and monthly thereafter for 10 months. The excised material was studied microscopically after being stained with hematoxylin and eosin, Verhoeff-van Gieson and succinic dehydrogenase. 70% of external sphincter specimens before internal sphincter excision showed smooth muscle fibers scattered between the striated fibers. These smooth fibers could be responsible for the resting tone of the external sphincter. After internal sphincter excision, characteristic histologic changes could be identified in the external sphincter. From the 2nd week to the 5th month after excision, the external sphincter showed degenerative and hypertrophic changes. From the 6th to the 10th month, there were regeneration of the striated muscle fibers and increase in the number of smooth fibers so that by the 10th month a 'compound' muscle of striated and smooth fibers was identified. Two theories were put forward to explain the smooth fiber preponderance in the external sphincter after internal sphincter excision: mutant and replacement theories. The increased nonstriated element in the external sphincter seems to be a structural-functional adaptation so that the external sphincter takes on the involuntary function of the excised muscle.     

Psychophysiological Profile in Dyssynergic Defecation Patients: An Individual and Situational Response Specificity Analysis

The aim of this study was to evaluate the temporal stability and the situational specificity of the intra-anal EMG-activity, as well as the individual specificity of this response in dyssynergic defecation patients. With this purpose, 26 individuals (13 with dyssynergic defecation and 13 without anorectal pathology) participated in two sessions of psychophysiological assessment, with an inter-session period of 1 week. At each session, the EMG-activity of external anal sphincter was recorded under four different conditions (baseline, voluntary contraction, reflex contraction and simulated defecation). The findings provide empirical evidence about temporal stability of the intra-anal EMG-activity, situational specificity of this response and the existence of a specific profile of intra-anal EMG-activity characteristic of patients with dyssynergic defecation.     

Third degree obstetric anal sphincter tears: risk factors and outcome of primary repair.

OBJECTIVES--To determine (i) risk factors in the development of third degree obstetric tears and (ii) the success of primary sphincter repair. DESIGN--(i) Retrospective analysis of obstetric variables in 50 women who had sustained a third degree tear, compared with the remaining 8553 vaginal deliveries during the same period. (ii) Women who had sustained a third degree tear and had primary sphincter repair and control subjects were interviewed and investigated with anal endosonography, anal manometry, and pudendal nerve terminal motor latency measurements. SETTING--Antenatal clinic in teaching hospital in inner London. SUBJECTS--(i) All women (n = 8603) who delivered vaginally over a 31 month period. (ii) 34 women who sustained a third degree tear and 88 matched controls. MAIN OUTCOME MEASURES--Obstetric risk factors, defecatory symptoms, sonographic sphincter defects, and pudendal nerve damage. RESULTS--(i) Factors significantly associated with development of a third degree tear were: forceps delivery (50% v 7% in controls; P = 0.00001), primiparous delivery (85% v 43%; P = 0.00001), birth weight > 4 kg (P = 0.00002), and occipito-posterior position at delivery (P = 0.003). No third degree tear occurred during 351 vacuum extractions. Eleven of 25 (44%) women who were delivered without instruments and had a third degree tear did so despite a posterolateral episiotomy. (ii) Anal incontinence or faecal urgency was present in 16 women with tears and 11 controls (47% v 13%; P = 0.00001). Sonographic sphincter defects were identified in 29 with tears and 29 controls (85% v 33%; P = 0.00001). Every symptomatic patient had persistent combined internal and external sphincter defects, and these were associated with significantly lower anal pressures. Pudendal nerve terminal motor latency measurements were not significantly different. CONCLUSIONS--Vacuum extraction is associated with fewer third degree tears than forceps delivery. An episiotomy does not always prevent a third degree tear. Primary repair is inadequate in most women who sustain third degree tears, most having residual sphincter defects and about half experiencing anal incontinence, which is caused by persistent mechanical sphincter disruption rather than pudendal nerve damage. Attention should be directed towards preventive obstetric practice and surgical techniques of repair.     

Neurophysiological evaluation of central-peripheral sensory and motor pudendal fibres

Extensive neurophysiological investigations were carried out in 18 healthy volunteer subjects, and 6 patients with neurological disease. The tests consisted of spinal and scalp somatosensory evoked potentials (SEPs) to stimulation of the dorsal nerve of penis/clitoris, motor evoked potentials (MEPs) from the bulbocavernosus muscle (BC) and anal sphincter (AS) in response to scalp and sacral root stimulation, and measurement of sacral reflex latency (SRL) from BC and AS.In the control subjects, the mean sensory total conduction time (sensory TCT), as measured at the peak of the scalp P40 wave was 40.9 msec (range: 37.8–44.2). The mean sensory central conduction time (sensory CCT = spine-to-scalp conduction time) was 27.0 msec (range: 23.5–30.4).Transcranial brain stimulation was performed by using a magnetic stimulator both at rest and during voluntary contraction of the examined muscle. Sacral root stimulation was performed at rest. Motor total conduction times (motor TCT) to BC and AS muscles were respectively 28.8 and 30.0 msec at rest, and 22.5 and 22.8 msec during contraction. Motor central conduction times (motor CCT) to sacral cord segments controlling BC and AS muscles were respectively 22.4 and 21.2 msec at rest, and 15.1 and 12.4 msec during contraction.The mean latencies of SRL were respectively 31.4 msec in the bulbocavernosus muscle and 35.9 msec in the anal sphincter. Combined or isolated abnormalities of SEPs, MEPs and SRL were found in a small group of patients with neurological disorders primarily or secondarily affecting the genito-urinary tract.     

术前经直肠腔内三维超声诊断复杂性肛瘘内口、分型的临床价值及对手术疗效的影响

摘要 目的：探讨术前经直肠腔内三维超声诊断复杂性肛瘘内口、分型的临床价值及对手术疗效的影响。方法：选择2021年1月至2022年6月我院收治拟行手术治疗的复杂性肛瘘患者84例,按照数字随机法分为研究组和对照组,每组42例。对照组术前行经直肠腔内常规超声检查,研究组术前行经直肠腔内三维超声检查。比较两组肛瘘内口术前诊断准确率、Parks分型检出准确率、手术疗效、住院时间、创口愈合时间,术前与术后肛门功能、术后并发症发生情况及复发率。结果：研究组肛瘘内口术前诊断准确率显著高于对照组（P<0.05）。研究组括约肌间型、经括约肌型、括约肌上型、括约肌外型术前诊断准确率显著高于对照组（P<0.05）。研究组治愈率为66.67%,显著高于对照组的42.86%（P<0.05）。研究组患者术后6个月肛门失禁Wexner 评分均显著低于对照组（P<0.05）,研究组患者住院时间、创面愈合时间均短于对照组（P<0.05）。两组术后并发症发生率、6个月内复发率比较无统计学差异（P>0.05）。结论：经直肠腔内三维超声诊断能够准确诊断肛瘘内口、瘘管走行,有利于提升复杂性肛瘘总体治疗效果,保护肛门功能。     

l-Arginine is a feasible supplement to heal chronic anal fissure via reducing internal anal sphincter pressure: a randomized clinical trial study

Amino Acids - The hypertonicity of internal anal sphincter resting pressure is one of the main causes of chronic anal fissure. Therefore, the aim of this study was to assess the effect of oral...