Mechanism Of Defecation Research Articles

Study on Intestinal Pressure after Implantation of Biaxial Actuated Artificial Anal Sphincter in Animal.

Fecal incontinence (FI) referred to the inability to control the leakage of solid, liquid, or gaseous feces, the artificial anal sphincter (AAS) was the last resort for patients with FI except enterostomy. In order to the clinical application value of AAS was improved, the detection and analysis of intestinal pressure information was very necessary. Biaxial actuated artificial anal sphincter (BAAS) was a new type of AAS, which not only had a stable, long-term and safe energy supply, but also could provide real-time feedback of intestinal pressure information. In this paper, the BAAS was implanted into piglets for a long-term animal experiment. Piglets' life habits, defecation habits and intestinal pressure were analyzed. The analysis results showed that the BAAS system had good feces control effect, when the actuator of the BAAS system was closed, there was basically no fecal leakage of piglets, and when the actuator of the BAAS system was opened, the piglets could defecate normally. Under the normal condition of the piglets' health state and the BAAS's operating state, the accuracy of the defecation perception reached to 65.79%. This study realized the in-depth study of the mechanism of piglets' defecation, and provided guidance for the development of a new generation of AAS.

Design of Novel Artificial Anal Sphincter

ObjectivesArtificial anal sphincter is considered to be a good method for the treatment of severe fecal incontinence, but there are problems of low biomechanical compatibility in clinical application. The purpose of this study is to design a novel artificial anal sphincter that can output stable loading force to solve the mechanical mismatch between artificial anal sphincter and intestinal tissue caused by excessive or too small local pressure on the intestine. Material and methodsAiming at the shortcomings of the existing artificial anal sphincter, a novel artificial anal sphincter with constant force mechanism is designed based on the C-shaped SMA sheet of Ti-55.9at%Ni and combined with the normal defecation mechanism of human body. In this paper, the chord length l of C-shaped SMA sheet is used as the design variable, and the artificial anal sphincter is optimized and verified initially by using finite element analysis method. ResultsThe results show that the artificial anal sphincter can achieve a constant force to clamp the intestine in a large displacement range when the chord length l of the C-shaped SMA is 13 mm, the chord height h is 1.5 mm, the width w is 2 mm, and the thickness δ is 0.2 mm. ConclusionThe design of artificial anal sphincter with constant force loading mechanism has a good effect in solving the biomechanical compatibility problem between the implant device and the intestinal tissue. In addition, the designed artificial anal sphincter occupies a small space, which provides a new idea for future clinical application.

Review of the indications, methods, and clinical utility of anorectal manometry and the rectal balloon expulsion test.

Anorectal manometry (ARM) comprehensively assesses anorectal sensorimotor functions. This review examines the indications, techniques, interpretation, strengths, and weaknesses of high-resolution ARM (HR-ARM), 3-dimensional high-resolution anorectal manometry (3D-HR-ARM), and portable ARM, and other assessments (i.e., rectal sensation and rectal balloon expulsion test) that are performed alongside manometry. It is based on a literature search of articles related to ARM in adults. HR-ARM and 3D-HR-ARM are useful for diagnosing defecatory disorders (DD), to identify anorectal sensorimotor dysfunction and guide management in patients with fecal incontinence (FI), constipation, megacolon, and megarectum; and to screen for anorectal structural (e.g., rectal intussusception) abnormalities. The rectal balloon expulsion test is a useful, low-cost, radiation-free, outpatient assessment tool for impaired evacuation that is performed and interpreted in conjunction with ARM. The anorectal function tests should be interpreted with reference to age- and sex-matched normal values, clinical features, and results of other tests. A larger database of technique-specific normal values and newer paradigms of analyzing anorectal pressure profiles will increase the precision and diagnostic utility of HR-ARM for identifying abnormal mechanisms of defecation and continence.

An integrated approach to the pathogenetic therapy of constipation

The data on the causes of defecation disorders, mechanisms of normal defecation, and pathogenetic aspects of constipation are presented. Functional gastrointestinal disorders are considered as a common pathology of the gastrointestinal tract, which is based on combined morphological and physiological abnormalities associated with visceral hypersensitivity, disorders of gastrointestinal motility, protective mucous barrier, immune function and the composition of the intestinal microbiota. The article discusses the possibility of using the drinking medicinal mineral water Zajecicka Horka (Zayechitskaya bitter) for intestinal pathology and other functional gastrointestinal disorders.

513 PHENOTYPIC CHARACTERIZATION OF FUNCTIONAL DEFECATORY DISORDERS USING SIMULTANEOUS MR DEFECOGRAPHY AND MANOMETRY

BACKGROUND & AIMS High resolution manometry (HRM) is widely used to diagnose defecatory disorders (DD). Contrary to conventional concepts, many healthy people have a negative rectoanal gradient during evacuation (ie, anal > rectal pressure), which undermines our understanding of the mechanisms of normal defecation and DD. Perhaps this is partly because manometry is performed in an empty rectum in the left lateral position. Aimed to better understand the mechanisms of normal defecation and DD, we simultaneously measured rectoanal pressures and evacuation in healthy and constipated women. METHODS We assessed anorectal and abdominal wall motion and rectal evacuation of gel with MR defecography, and pressures with water-perfused manometry in 28 healthy women and 26 women with constipation. Phenotypes were identified by K-means cluster analysis. The unconditional exact test (chi-squared statistic) evaluated the relationship between these clusters and outcomes, ie, balloon expulsion time [BET], subject status (healthy versus constipation) and evacuation. RESULTS Twenty seven participants (19/27 healthy women, 8/26 patients, P 25% of gel). The BET was >60s in 4 controls and 9 patients (P=0.1). The cluster analysis identified 3 distinct clusters, which were defined by pressure and motion variables (Figure 1); BET and rectal evacuation were not variables in the cluster analysis. During evacuation, the rectal pressure, anorectal junction descent, abdominal diameter, and anal diameter were all smaller while the anal canal was longer in cluster 1 (3 evacuators [E], 21 nonevacuators [NE]) (P CONCLUSIONS Manodefecography uncovers 3 clusters in DD. Cluster 1, which predominantly comprises nonevacuators, is characterized by limited abdominal expansion, a spastic pelvic floor, and inadequate rectal pressure during evacuation. By contrast to cluster 1, 24 of 30 (80%) subjects in clusters 2 and 3 were evacuators. In these subjects, abdominal expansion, rectal pressure, and anal opening were preserved; resting anal pressure was lower in cluster 2 than 3. Most patients with DD do not have isolated rectal or anal dysfunctions but rather a combination of impaired abdominal expansion, rectal propulsion, anal opening, and perineal descent during evacuation. Download : Download high-res image (170KB) Download : Download full-size image Figure 1 . The cluster analysis, which was based of 7 variables (Table 1), uncovered 3 distinct clusters. These clusters are plotted using the first two principal components from the 7 variables. The principal component analysis is only used to depict the data; it was not used for the K-means cluster analysis. Cluster 1 predominantly comprises nonevacuators (filled symbols), while clusters 2 and 3 are predominantly evacuators (open symbols). These clusters (1 versus 2 and 3) were associated with evacuator status (P Download : Download high-res image (69KB) Download : Download full-size image Table 1 . Table showing the values of the variables corresponding to centroids of the clusters. During evacuation(e), cluster 1 (3 evacuators[E], 21 nonevacuators [NE]) had lower rectal pressure, anorectal junction descent, abdominal diameter, anal diameter, and a longer anal canal. Cluster 2 (15 E, 4 NE) was characterized by lower anal resting pressure. Compared to clusters 1 and 2, patients in cluster 3 (9 E, 2 NE) had greater anal resting pressure but more anal relaxation during evacuation.

What Is Fecal Incontinence That Urologists Need to Know?

Fecal incontinence (FI) undoubtedly reduces quality of life and adversely affects the social life of the affected individual. FI has a higher prevalence with age and has an equivalent prevalence to urinary incontinence in patients with genitourinary disease, but is often not confirmed in these cases. A thorough investigation is needed to diagnose FI, with the common etiology of this condition in mind, and several questionnaires can be used to identify symptoms. The physical examination contains digital rectal examination carries out to identify the patient’s condition. Ultrasound, colonoscopy, and rectum pressure test can be performed. Patients educated in diet-related issues, bowel movements, and defecation mechanism. Nonoperative options such as diet control and Kegel exercise should be performed at first. Surgical treatment of FI is considered when conservative management and oral medications produce no improvement. Surgical options include less invasive procedures like bulking agent injections, and more involved approaches from sacral nerve stimulation to invasive direct sphincter repair and artificial bowel sphincter insertion. Good outcomes in FI cases have also recently been reported for barrier devices.

Laparoscopic Management of Perineal Descent Syndrome in Pediatric Age Group

ABSTRACT Background: Perineal descent syndrome is a disease that affects the pelvic floor because of denervation of its muscles, resulting in obstructed defecation. Hints on the anatomy that may be associated with the work got, and the physiology of the anorectum was explained, discussing factors leading to continence and mechanism of defecation was presented. Objective: to diagnose the perineal descent syndrome in both cases of chronic constipation and anal incontinence and the use of laparoscopy in the management of PDS in children where the pathophysiologic changes for each case is identified and dealt with laparoscopically. Patients and Methods: This study was a prospective case study that had been conducted in pediatric surgery department, Al-Azhar university hospitals during the period from June 2019 to June 2020 after approval from the ethical review committee of Al-Azhar faculty of medicine. The study included 30 patients presented to the outpatient clinics with constipation or Fecal incontinence whom fulfilled the required Criteria. Results: In our study (n=30), 2 recurrent cases (13.3%) were found after laparoscopic suture rectopexy. Recurrence rates with mesh rectopexy or resection rectopexy was zero % and chronic conistipation and fecal incontinence are considered as a hidden cause for perineal descent syndrome. Conclusion: The anterior rectal wall has a great dynamic role in defecation thanks to its viscoelastic properties. Any rectopexy technique should never interfere or impede this vital mechanism of action. Finally chronic conistipation and fecal incontinence are considered as a hidden cause for perineal descent syndrome.

Etiology and management of low anterior resection syndrome based on the normal defecation mechanism.

Low anterior resection syndrome (LARS) commonly develops after an anal sphincter-preserving operation (SPO). The etiology of LARS is not well understood, as the anatomical components and physiological function of normal defecation, which may be damaged during the SPO, are not well established. SPOs may damage components of the anal canal (such as the internal anal sphincter, longitudinal conjoint muscle, or hiatal ligament), either mechanically or via injury to the nerves that supply these organs. The function of the rectum is substantially impaired by resection of the rectum, division of the rectococcygeus muscle, and/or injury of the nervous supply. When the remnant rectum is small and does not function properly, an important functional role may be played by the neorectum, which is usually constructed from the left side of the colon. Hypermotility of the remnant colon may affect the manifestation of urge fecal incontinence. To develop an SPO that minimizes the risk of LARS, the anatomy and physiology of the structures involved in normal defecation need to be understood better. LARS is managed similarly to fecal incontinence. In particular, management should focus on reducing colonic motility when urge fecal incontinence is the dominant symptom.

Descending monoaminergic pathways projecting to the spinal defecation center enhance colorectal motility in rats.

The central regulating mechanisms of defecation, especially roles of the spinal defecation center, are still unclear. We have shown that monoamines including norepinephrine, dopamine, and serotonin injected into the spinal defecation center cause propulsive contractions of the colorectum. These monoamines are the main neurotransmitters of descending pain inhibitory pathways. Therefore, we hypothesized that noxious stimuli in the colorectum would activate the descending monoaminergic pathways projecting to the spinal defecation center and that subsequently released endogenous monoamine neurotransmitters would enhance colorectal motility. Colorectal motility was measured in rats anesthetized with α-chloralose and ketamine. As a noxious stimulus, capsaicin was administered into the colorectal lumen. To interrupt neuronal transmission in the spinal defecation center, antagonists of norepinephrine, dopamine, and/or serotonin receptors were injected intrathecally at the L6-S1 spinal level, where the spinal defecation center is located. Intraluminal administration of capsaicin, acting on the transient receptor potential vanilloid 1 channel, caused transient propulsive contractions. The effect of capsaicin was abolished by surgical severing of the pelvic nerves or thoracic spinal transection at the T4 level. Capsaicin-induced contractions were blocked by preinjection of D2-like dopamine receptor and 5-hydroxytryptamine subtype 2 and 3 receptor antagonists into the spinal defecation center. We demonstrated that intraluminally administered capsaicin causes propulsive colorectal motility through reflex pathways involving the spinal and supraspinal defecation centers. Our results provide evidence that descending monoaminergic neurons are activated by noxious stimulation to the colorectum, leading to facilitation of colorectal motility. NEW & NOTEWORTHY The present study demonstrates that noxious stimuli in the colorectum activates the descending monoaminergic pathways projecting to the spinal defecation center and that subsequently released endogenous monoamine neurotransmitters, serotonin and dopamine, enhance colorectal motility. Our findings provide a possible explanation of the concurrent appearance of abdominal pain and bowel disorder in irritable bowel syndrome patients. Thus the present study may provide new insights into understanding of mechanisms of colorectal dysfunction involving the central nervous system.

How Do We Evacuate Stool? Insights From Combined High-Resolution Anorectal Manometry With Defecography

Introduction: The sense of incomplete evacuation is a feature of a defecatory disorder- however the mechanism of evacuation is not well understood. The aim of this study was to use simultaneous barium defecography and high resolution anorectal manometry (HRAM) to elucidate the mechanism of defecation in patients and controls Methods: Simultaneous seated HRAM and defecography (using180ml barium paste) were performed in 26 constipated women and 22 asymptomatic controls. Anal diameter and rectal pressures during evacuation and percentage of barium emptied, and the rectoanal pressure gradient during evacuation were calculated. Values less than 25th percentile for controls was considered abnormal. Results: Healthy women evacuated 80% of barium paste (median, IQ range-18-90%) while patients evacuated 21% (0-70%). Five controls and 12 patients evacuated < 18% of barium (25th percentile for controls). They were classified as “poor-evacuators” or PE); of these 9 had an abnormal balloon expulsion test (>60 seconds). The rest were classified as “adequate evacuators” (AE). Rectal and anal pressures increased initially during evacuation in all women. Thereafter, anal pressures declined, but the rectoanal pressure gradient exceeded 0 mm Hg only in AEs, enabling evacuation in this group. Rectal pressure at the onset of evacuation (median 87 vs 47mmHg, p=0.1) and anal diameter during evacuation (13 vs 0mm, p=0.002) was greater in AEs than PEs. Among AEs, a moving average of recto-anal pressure gradients (median = 4.2 mmHg) was positive (>0 mm Hg) for a median duration of 5s, which is 60% of the median duration of evacuation (8.5s). Among constipated PEs, disturbances were inadequate rectal pressure (4 patients) or impaired anal relaxation (8 patients). In a multivariate linear regression model, the rectoanal gradient, average anal canal diameter, and duration of anal relaxation during evacuation explained 40% of the variation in percent of barium emptied (p=0.0001). Conclusion: Adequate evacuation of barium (≥18%) is characterized by an initial simultaneous increase in rectal and anal pressure followed by anal relaxation. Conversely, either an inadequate increase in rectal pressure or in anal diameter during evacuation leads to incomplete evacuation. Not all women who have poor evacuation are symptomatic. The simultaneous increase in rectal and anal pressures during evacuation may be mediated by a reflex induced by increased abdominal pressure. Simultaneous defecography with HRAM may be useful in the clinical evaluation of chronic constipation.

Sa1647 - Sex Differences in Anorectal Pressures and Mechanisms of Defecation in Healthy People

Sa1647 - Sex Differences in Anorectal Pressures and Mechanisms of Defecation in Healthy People

Défécographie chez des volontaires sains: résultats et implications

Forty-seven healthy young volunteers underwent defecographic examination to determine the range of normal findings. Normality was shown to encompass radiological features often considered pathological. These features included broad ranges of anorectal angle and pelvic floor descent which overlap with reported pathological states. Furthermore, the formation of rectocoeles during defecation was a very common finding in women. Finally, a subgroup of the volunteers had marginal anorectal function. The marginal anorectal function and certain radiological findings such as rectocoeles or intussusceptions may predispose to later problems, or contribute to clinical problems when combined with other factors such as dietary fibre deficiency. The radiological findings raise a number of questions with respect to different aspects of the functioning of the continence and defecation mechanisms.

Sigmoid compliance and visceral perception in spinal cord injury patients

Intestinal motor and sensory dysfunctions in traumatic complete or incomplete spinal cord injury (SCI) are frequent and result in altered mechanisms of defecation. The aim of this study is to investigate sigmoid compliance and perception in chronic SCI patients. Sigmoid responses to fixed-tension distentions were assessed using a tensostat in six patients (six men, 42 ± 4 years) with chronic complete transection of the spinal cord (high-SCI; five tetraplegic C5-C7 and one paraplegic T4-T6) and impaired evacuation (i.e. constipation). A group of 10 healthy individuals (six men, 25 ± 1 years) served as controls. SCI patients had higher sigmoid compliance at the highest distention level than the controls (10.3 ± 2.4 vs. 5.1 ± 0.8 ml/mmHg; P<0.05). Perception scores at first sensation were higher in SCI patients (2.3 ± 0.7 vs. 1.1 ± 0.1; P<0.05), but were not different at the highest distention levels (3.7 ± 0.8 vs. 3 ± 1; NS). The most commonly reported sensation by patients was distention/bloating and was referred less commonly to the hypogastrium compared with distention/bloating in controls. An increased sigmoid compliance can be detected in constipated SCI patients. The preservation of some degree of visceral sensations, although abnormally referred, could imply the occurrence of sensory input remodeling at the spinal level.

Avaliação manométrica anal de crianças com encoprese

INTRODUÇÃO: A constipação crônica é doença comum na infância, ocorrendo em 5 a 10% dos pacientes pediátricos, considerada a segunda maior causa de procura nos consultórios de pediatria, sendo a encoprese decorrente de constipação grave associada à impactação fecal no reto. Dentre os exames diagnósticos, a manometria anal é utilizada para a avaliação de pacientes com distúrbios funcionais, como a constipação intestinal e a incontinência fecal, em alguns serviços para a avaliação de pacientes com encoprese, pois pode trazer informações sobre o mecanismo evacuatório e possíveis lesões esfincterianas anais. OBJETIVO: Verificar alterações manométricas em pacientes com encoprese. MÉTODOS: Foi realizado estudo de 40 manometrias anais de crianças constipadas com encoprese (G1) e 12 crianças constipados sem encoprese (G2). Foram obtidos os seguintes dados: pressões de repouso, contração e evacuação do canal anal e ampola retal, ponto de maior pressão, reflexo inibitório anal e sensibilidade retal. As manometrias foram realizadas com o aparelho Alacer de perfusão com 8 canais. RESULTADOS: Não foram encontradas diferenças nas pressões de repouso, contração e evacuação do canal anal entre os grupos. Chamou-nos a atenção a ausência de necessidade de maior volume retal para desencadear o reflexo inibitório anal. Não houve diferença da incidência de anismus entre os dois grupos, demonstrando que não se trata de fator importante na manutenção da encoprese, mas sim da constipação. CONCLUSÃO: Não houve necessidade de maior volume para desencadear o reflexo inibitório anal. O anismus não foi diferente entre os dois grupos, não sendo importante na manutenção da encoprese.

Role of anorectal manometry in children with severe constipation

Constipation is one of the most frequent disorders of the digestive tract in children and it can be an important problem in paediatric and surgical practice. Most of the time, the cause is psychological or because of a slowing of colonic transit, but it can be a sign of organic gastrointestinal outlet obstruction. Some patients with chronic constipation are resistant to a medical approach and they present with a severe form of constipation that needs recurrent hospital admission. Anorectal manometry (ARM) is a noninvasive procedure and it helps to explain the mechanisms of defecation disorders. The aim of the present study was to evaluate the role of ARM in children with severe constipation. From October 2003 to October 2006, in the Paediatric Surgery Unit, 85 children - aged more than 1 year - with severe constipation were seen. The mean age was 5 years (range, 1-13). At presentation, every child had abdominal and rectal examination in order to identify abdominal distension or faecal masses. Bowel preparation with enemas was performed before ARM in patient with a rectal faecaloma. Myoelectric activity of the internal anal sphincter and resting anal tone was recorded; recto-anal inhibitory reflex (RAIR) was tested to exclude Hirschsprung's disease (HD). Anal tone was considered normal until 50 cm H(2)O. When the RAIR was absent, the patient underwent rectal suction biopsies (RSB) for histology and acetylcholinesterase histochemistry. In cases of normal or high anal tone with the RAIR present, the child had bowel cleaning, medical treatment, 2- and 6-month follow-up. Children with ineffective treatment at follow-up underwent RSB. In case of HD, a laparoscopic-assisted endorectal pull-through (ERPT) according to Georgeson's technique was performed. Seventy per cent of the patients had bowel preparation before ARM. In four patients the ARM was impossible to assess because of crying. In 28 patients, the anal tone result was higher than 50 cm H(2)O and local treatment with anaesthetic agents was used for 8 weeks. Seventeen patients underwent RSB: 11 patients with RAIR absent/unclear, 4 noncooperative children and 2 patients with ineffective medical treatment at follow-up. HD was diagnosed in 2 patients and laparoscopic-assisted ERPT was performed. The remaining patients had good results at 6-month follow-up. ARM is a noninvasive diagnostic tool to study the mechanism of defecation in children with constipation in order to prescribe the appropriate treatment. This procedure can be used in every child - aged more than 1 year - with severe constipation and assessment of the RAIR can select the cases for RSB.

Pelvic floor: anatomy and function

The pelvic floor is a dome-shaped striated muscular sheet that encloses the bladder, uterus, and rectum, and, together with the anal sphincters, has an important role in regulating storage and evacuation of urine and stool. This article reviews the anatomy, nerve supply, pharmacology, and functions of the anal sphincters and the pelvic floor. The internal and external anal sphincters are primarily responsible for maintaining faecal continence at rest and when continence is threatened, respectively. Defecation is a somato-visceral reflex regulated by dual nerve supply (i.e. somatic and autonomic) to the anorectum. The net effects of sympathetic and cholinergic stimulation are to increase and reduce anal resting pressure, respectively. Faecal incontinence and functional defecatory disorders may result from structural changes and/or functional disturbances in the mechanisms of faecal continence and defecation.

Defecation mechanisms after anterior resection with J-pouch-anal and side-to-end anastomosis in dogs

Colonic J-pouch-anal anastomosis or colonic side-to-end anastomosis is the reconstruction of choice after low anterior resection. However, the mechanisms of defecation after both reconstruction forms are still speculative. Low anterior rectal resections were performed in 12 dogs with six colonic J-pouch-anal (pouch) and six coloanal side-to-end (SE) reconstructions. Four months postoperative stool frequency, intestinal transit time, and neorectal compliance were determined by radiography and barostat. Defecation mechanisms were evaluated radiographically during expulsion of artificial stool. One dog with pouch reconstruction could not be evaluated due to an anastomotic leak, while the others had uncomplicated course. Spontaneous stool frequency was significantly increased with both reconstruction methods (control 2.0+/-0.9, pouch 2.7+/-1.2, SE 3.3+/-0.9 day; p<0.05). Intestinal transit time was significantly higher with pouch reconstruction due to storage of stool in the pouch and the descending colon compared to SE (control 760+/-82, pouch 592+/-97, SE 550+/-87 min; p<0.05). Compliance and functional capacity were higher in pouch than in side-to-end reconstructions (pouch 5.0+/-0.7 ml/mmHg, 124+/-23 ml; SE 2.7+/-0.3 ml/mmHg, 92+/-24 ml; p<0.05). During defecation, there were no contractions of the pouch detectable. The colonic J-pouch reconstruction results in better functional outcome than side-to-end coloanal anastomosis. Our results show that pouch evacuation is passive and independent from pouch motility. The functional principle of the colonic J-pouch is not its reservoir function but a delay of colonic motility.

Functional anatomy of rectum and anus

The anatomical structures of the rectum and anus are a functional unit designed to maintain continence mechanism. A pure anatomical description often fails to delineate this critical functional interaction. The topographic anatomy of the anorectum must be combined with an understanding of the mechanisms of anal continence and defecation, which can be transferred to clinical and especially surgical practice. The feedback-controlled reflex system of continence must be understood; it hinges on a complex interaction between the somatic and autonomic nervous systems.

Defecation mechanisms after proctocolectomy and ileal pouch--anal anastomosis in dogs.

The role of intrinsic pouch motility after ileal pouch-anal anastomosis (IPAA) during defecation is still speculative. IPAA was performed in 12 dogs. Defecation mechanisms were evaluated by motility recordings during spontaneous defecation and during expulsion of an endoluminal balloon and by radiography with sequential sector-related gray scale analysis. Spontaneous defecations appeared without significant changes in electrical or mechanical activity of the pouch. Sequential filling of the pouch led to defecation in only seven dogs while the others did not succeed in emptying their pouch even with maximal balloon inflation. Neither strain gauge measurements nor electromyography demonstrated peristaltic contractions of the pouch during defecation while sector-related gray scale analysis revealed strong contractions of the abdominal wall during pouch emptying. Pouch emptying is independent of intrinsic pouch motility. The ileoanal pouch acts as a functionally passive reservoir, and its evacuation is initiated by a rise of the intra-abdominal pressure.

Colorectal motility induction by sacral nerve electrostimulation in a canine model: implications for colonic pacing.

This study investigated the role of the sacral nerves in the mechanism of defecation using adult mongrel dogs. The possibility of designing a colonic pacemaker as a new therapeutic device to treat defecation disturbances, such as fecal incontinence and severe constipation, is also discussed. Colorectal motility during spontaneous defecation was monitored with force strain-gauge transducers implanted in the proximal, distal, and sigmoid colon, rectum, and internal anal sphincter. Under general anesthesia, the sacral nerve was stimulated electrically, and the colorectal motility response was examined. During spontaneous defecation, three characteristic motility patterns were observed: 1) giant migrating contractions of the colon were propagated to the rectum or anus; 2) the rectum relaxed before the giant migrating contractions were propagated; and 3) the internal anal sphincter was relaxed during the propagation of the giant migrating contraction. Sacral nerve stimulation elicited the following three unique responses: 1) contractile movements were propagated from the distal colon to the rectum; 2) a relaxation response was noted in the rectum; and 3) the internal anal sphincter exhibited a relaxation response. The duration and propagation velocity of the contractile responses and the duration of relaxation responses elicited by electrical stimulation of the sacral nerve were similar to those that occurred during spontaneous defecation, but their amplitudes were smaller. The coordinated processes of the colon and anorectum during defecation were affected by the sacral nerves. This suggests that it is possible to design a colonic pacemaker to control lower colonic and rectal movements.