Sigmoido-rectal junction reflex: role in the defecation mechanism

Excessive bowel volume loss during anus-preserving surgery for rectal cancer affects the bowel function after operation: A prospective observational cohort study (Bas-1611)

Background

Bowel volume loss during anus-preserving surgery (APS) may result in low anterior resection syndrome (LARS). We conducted this prospective observational cohort study to measure the incidence of LARS after surgery and evaluate the relationship between bowel volume loss and bowel function.

Methods

Patients with R0 resectable rectal cancer who consented to several bowel function surveys through telephone interviews after the operation were included. Enrolled patients underwent standard APS for rectal cancer, and three length indexes, viz. length of excised bowel, length of the distal margin and length of the proximal margin (LPM) of fresh bowel specimens, were measured in vitro.

Results

The three measured variables of the specimens showed a positively skewed distribution. Patient interviews revealed a trend of gradual improvement in bowel function. Univariate analyses revealed that longer LPM was associated with a significantly negative impact on bowel function at all time points. In multivariate analysis, LPM was found to be a significant risk factorstatistically significant, but its impact was not as strong as that of radiotherapy and low-middle tumour. Furthermore, there was no significant difference in the lymph node detection rate between <10-cm and ≥10-cm LPM groups.

Conclusion

In APS for rectal cancer, bowel volume loss is an important factor causing postoperative bowel dysfunction. Controlling LPM to <10 cm may help improve postoperative bowel function.

The Sphincter of O'Beirne - Part 1: Study of 18 Normal Subjects

BACKGROUND

Gastroenterologists have ignored or emphasized the importance of the rectosigmoid junction in continence or constipation on and off for 200 years. Here, we revisit its significance using high-resolution colonic manometry.

METHODS

Manometry, using an 84-channel water-perfused catheter, was performed in 18 healthy volunteers.

RESULTS

The rectosigmoid junction registers as an intermittent pressure band of 26.2 ± 7.2 mmHg, or intermittent phasic transient pressure increases at a dominant frequency of 3 cpm and an amplitude of 28.6 ± 8.6 mmHg; or a combination of tone and transient pressures, at a single sensor, 10-17 cm above the anal verge. Features are its relaxation or contraction in concert with relaxation or contraction of the anal sphincters when a motor pattern such as a high-amplitude propagating pressure wave or a simultaneous pressure wave comes down, indicating that such pressure increases or decreases at the rectosigmoid junction are part of neurally driven programs. We show that the junction is a site where motor patterns end, or where they start; e.g. retrogradely propagating cyclic motor patterns emerge from the junction.

CONCLUSIONS

The rectosigmoid junction is a functional sphincter that should be referred to as the sphincter of O'Beirne; it is part of the "braking mechanism," contributing to continence by keeping content away from the rectum. In an accompanying case report, we show that its excessive presence in a patient with severe constipation can be a primary pathophysiology.

Comparison of the effects of colonic electrical stimulation and prucalopride on gastrointestinal transit and defecation in a canine model of constipation

OBJECTIVE

The aim of this study was to compare the effects of colonic electrical stimulation (CES) and prucalopride on gastrointestinal transit and defecation and to verify the safety of CES in a canine model of constipation.

METHODS

Eight beagles received CES implantation and induction drugs for slow transit constipation (STC). In the STC model, the gastrointestinal transit time (GITT), colonic transit time (CTT), stool frequency and stool consistency were assessed to compare the effects of CES and prucalopride on gastrointestinal transit and defecation. The histocompatibility of the implantable device was evaluated.

RESULTS

The individualized parameters for CES varied greatly among the animals, and the GITTs were not significantly shortened by CES or prucalopride; however, both the CES and prucalopride treatment significantly accelerated CTT and improved stool consistency compared with sham stimulation. CES treatment also resulted in significantly higher stool frequency than prucalopride treatment, which did not significantly change the stool frequency. No severe inflammation response was detected in the gross and microscopic appearance around the implants.

CONCLUSION

CES and prucalopride treatment may yield similar short-term effects for improving gastrointestinal transit and stool consistency, and CES outperformed prucalopride treatment in terms of defecation inducement in the short term. There were ideal levels of endurance and histocompatibility for the animals that underwent CES.

Effects of colonic electrical stimulation using different individual parameter patterns and stimulation sites on gastrointestinal transit time, defecation, and food intake

PURPOSE

This study aimed to compare the effects of colonic electrical stimulation (CES) on gastrointestinal transit time (GITT), energy consumption, stool frequency, stool consistency, and food intake using different individual parameter patterns and stimulation sites.

METHODS

Eight beagle dogs underwent surgery and CES. First, CES was conducted to determine the individual parameters with different pulse configurations, based on symptoms. Second, influences on energy consumption and GITT were compared between CES sessions with different pulse configurations. Third, GITT, stool frequency, stool consistency, and food intake were compared to assess the effects of CES at different stimulation sites.

RESULTS

The individual parameters varied greatly among the dogs. In proximal colon electrical stimulation (PCES) and rectosigmoid colon electrical stimulation (RCES), energy consumption was lower with the constant pulse width mode than with the constant pulse amplitude mode (p = 0.012 and p = 0.018, respectively). There was no statistical difference between the two pulse configurations in GITT assessment. The PCES, RCES, and sequential CES sessions significantly accelerated GITT compared to sham stimulation. There was no statistical difference in GITT between PCES, RCES, and sequential CES sessions. Compared to sham CES session, RCES and sequential CES sessions exhibited significant higher stool frequency (p < 0.001 and p = 0.001, respectively), and PCES and RCES sessions inhibited food intake (p = 0.003 and p = 0.002, respectively).

CONCLUSIONS

Constant pulse width mode is an appropriate pulse configuration for individual CES. At different stimulation sites, CES may exert different effects on stool frequency and food intake. This study provides an experimental basis for the clinical application of CES.

A clinicopathological study of serotonin of sigmoid colon mucosa in association with chronic symptoms in uncomplicated diverticulosis

INTRODUCTION

Neurotransmitter imbalance is hypothesised as a pathogenetic mechanism in several bowel conditions. We previously reported increased 5-HT in the sigmoid mucosa of colon resected for complicated diverticular disease (DD). We aimed to identify if abnormal 5-HT expression is associated with symptoms of uncomplicated DD.

METHODS

This was a prospective, comparative study and follow-up survey of symptoms. We examined the differences in 5-HT between DD patients and controls, as well as the presence of bowel symptoms at time of endoscopy and also 2 years later. Sigmoid biopsies were collected at colonoscopy. Immunohistochemical staining for 5-HT cells was performed.

RESULTS

Eighty-seven patients were recruited, 37 (42.5 %) DD and 50 (57.5 %) controls. No patients underwent surgery. There was no significant difference in total mean number of 5-HT-positive cells in DD compared to controls or between patients and controls with abdominal symptoms. Forty-one patients (47.1 %) responded to questionnaires at median 57.8 months from biopsy. Eighteen (43.9 %) were DD and 23(56.1 %) controls. 5-HT counts showed no significant association to symptom persistence.

DISCUSSION

Although 5-HT expression has previously been found to be increased in complicated DD in whole bowel-resected specimens, the same is not confirmed on colonic mucosal biopsies. This raises the suggestion that 5-HT may be involved in the development of acute complications but may not be involved in the pathogenesis of chronic symptoms.

The physiology of human defecation

Human defecation involves integrated and coordinated sensorimotor functions, orchestrated by central, spinal, peripheral (somatic and visceral), and enteric neural activities, acting on a morphologically intact gastrointestinal tract (including the final common path, the pelvic floor, and anal sphincters). The multiple factors that ultimately result in defecation are best appreciated by describing four temporally and physiologically fairly distinct phases. This article details our current understanding of normal defecation, including recent advances, but importantly identifies those areas where knowledge or consensus is still lacking. Appreciation of normal physiology is central to directed treatment of constipation and also of fecal incontinence, which are prevalent in the general population and cause significant morbidity.

Embryology and anatomy of the vesicoureteric junction with special reference to the etiology of vesicoureteral reflux

Concerning the ureterovesical junction - the region most important for the anti-reflux mechanism - there is still a lot of misunderstanding and misinterpretation with regard to normal fetal development. Data are scarce on possible causes of primary vesicoureteral reflux and on involved mechanisms of the so-called maturation process of refluxing ureteral endings. The ratio of the intravesical ureteral length to the ureteral diameter is obviously lower than assumed so far, as clearly revealed by some studies. Therefore it can be doubted that the length and course of the intravesical ureter is of sole importance in the prevention of reflux. Additionally refluxing intravesical ureteral endings present with dysplasia, atrophy, and architectural derangement of smooth muscle fibers. Besides, a pathologically increased matrix remodeling combined with deprivation of the intramural nerve supply has been confirmed. Consequently, symmetrical narrowing of the very distal ureteral smooth muscle coat creating the active valve mechanism to defend reflux is not achievable. It is apparent that primary congenital vesicoureteral reflux seems to be the result of an abnormality within the ureterovesical junction with an insufficient muscular wrap. Nature is believed to establish much more sophisticated mechanisms than the so-called passive anti-reflux mechanism. Remodeling processes within the ureterovesical junction of refluxing ureteral endings support that maturation itself is nothing else than wound or defect healing and not a restitution of a morphological normal ureterovesical junction. Lacking the nerve supply a restoration of any muscular structure can not be achieved.

Review article: the pathogenesis of diverticular disease--current perspectives on motility and neurotransmitters

BACKGROUND

Low-fibre diet, structural abnormalities and ageing are traditional aetiological factors implicated in the development of diverticular disease. More recently, motility disorders are implicated in its causation leading to speculation that neurotransmitters play a role in mediating these disturbances.

AIMS

To draw together studies on the role of neurotransmitters in the development of diverticular disease and its symptoms.

METHODS

Medline, GoogleScholar and Pubmed were searched for evidence on this subject using the terms neurotransmitters, motility, diverticular disease and pathogenesis. Articles relevant to the subject were cited and linked references were also reviewed.

RESULTS

Serotonin, which has been found to be an excitatory colonic neurotransmitter, has been found in early studies to be increased in colonic enterochromaffin cells. Acetylcholine, which is thought to be an excitatory neurotransmitter and cholinergic activity, has also seen to be increased in diverticular disease. These findings may suggest that an increase in excitatory neurotransmitters may result in the hypersegmentation thought to cause pulsion diverticula. Similarly, a decrease in nitric oxide which is inhibitory is found.

CONCLUSIONS

There is some evidence that neurotransmitters may play a role in the motility disturbances seen in diverticular disease; however, a clear role is yet to be ascertained.

Anatomofisiología de la continencia y la defecación

Continence and defecation are two essential functions in humans. Any alteration resulting in anal incontinence and/or constipation can severely impair the patient's quality of life. This study analyzes the anatomical structures and physiologic mechanisms accepted as factors involved in the correct development of both functions, while recognizing that there are still many unclear issues within this complex and sometimes paradoxical structure/function of the human body.

Fetal development of the vesico-ureteric junction, and immunohistochemistry of the ends of refluxing ureters

There is still misunderstanding about the normal fetal development of the vesico-ureteric junction (VUJ), the region that is most important for preventing VUR. There is little information on the causes of primary VUR and on the mechanisms of maturation of refluxing ureteric endings. Some studies show that the ratio of the intravesical ureteric length to diameter is obviously lower than had been assumed. It is doubtful that the length and course of the intravesical ureter is the sole factor in preventing reflux, as previously reported. The intravesical part of refluxing ureters shows dysplasia, atrophy and architectural derangement of smooth muscle fibres. A pathologically increased matrix remodelling combined with deprivation of the intramural nerve supply has been confirmed. Consequently, symmetrical contraction of the distal ureteric smooth muscle coat, creating the active valve mechanism to prevent reflux, is impossible. We reviewed publications using Medline, with the keywords 'human fetal development', 'embryology', 'ureterovesical junction', relevant 'growth data', 'vesico-ureteric reflux', 'children', 'immunohistochemistry', 'extracellular matrix', and 'nerve supply', respectively. Priority was given to articles that correlated specific embryological findings and basic research on possible mechanisms to the genesis and maturation of the VUJ.

Longitudinal and thickness measurement of the normal distal and intravesical ureter in human fetuses

PURPOSE

We define reference data concerning the development of the ureterovesical junction in fetuses and newborns by measuring the diameters of the distal mesenchymal and muscular ureteral walls as well as intravesical ureteral length.

MATERIALS AND METHODS

A total of 90 normal fetal and newborn ureters were investigated. Our histological studies were based on "plastinated" sections of whole pelves which allow study of the sectional anatomy of the distal and intravesical ureter. The development of the mesenchymal and smooth muscle growth of the distal and intravesical ureter was examined. The ureteral measurements were correlated with age of gestation.

RESULTS

The length of the intravesical ureter and mesenchymal as well as smooth muscle walls increased in a linear mode. Significant correlations (p <0.0001) were found between gestational age and the growth of the mesenchymal as well as smooth muscle walls in the distal intravesical ureter as well as the length of the intravesical ureter.

CONCLUSIONS

Significant positive linear relationships exist between gestational week, and distal and intravesical ureteral wall thickness of the mesenchymal and smooth muscle growth to the length of the intravesical ureter in fetuses and newborns. The ratio of the intravesical ureteral length-to-ureteral diameter is obviously lower than assumed previously. Data from this study can be used for a more accurate assessment of cases with abnormal lower urinary tract development.

Identification of a sphincter at the sigmoidorectal canal in humans: histomorphologic and morphometric studies

In a recent study we demonstrated that the rectosigmoid junction is a large bowel segment 2.8 +/- 0.9 cm in length, which we have termed the 'sigmoidorectal canal' (SRC). In that study we showed that the SRC exerted increased intraluminal pressure, contained a thick, circular, smooth muscle layer, and reacted to sigmoid colon (SC) and rectal contraction by relaxation and contraction, respectively. These findings suggest the existence of an anatomical sphincter at the SRC. To investigate this hypothesis, in the present study we carried out a morphometric (quantitative) analysis of the musculature of the SC, SRC, and rectum. Twenty-two cadavers (13 male, 9 female; mean age = 32.3 +/- 17.6 years) were investigated. Histomorphologic studies comprised staining transverse (15 cadavers) and longitudinal (7 cadavers) sections from the SC, SRC, and rectum. Specimens were stained with H&E, Masson's trichrome, and silver stains. Morphometric studies, using image analyzer computer equipment, measured the muscle thickness of the muscularis externa (ME) of the SC, SRC, and rectum. The ME of the SRC was markedly thickened compared to the ME of the SC or rectum. In 16 specimens, the increased thickness involved mainly the circular muscle layer and in six specimens both the circular and longitudinal layers. Connective tissue septa connected the adventitia with the submucosa: these 'adventitial septa' contained nerve ganglia. 'Localized bundles' of smooth muscle fibers were detected between the circular muscle fibers. The morphometric findings showed that the mean thickness of the circular muscle layer measured 440.3 +/- 80.1 microm in the SC, 1166.1 +/- 255.4 microm in the SRC, and 394.9 +/- 123.9 microm in the rectum. This study strongly suggests the presence of an anatomic sphincter at the SRC. This sphincter may explain the higher pressure at the SRC and the response of the SRC to rectal and SC contractions. The localized smooth muscle bundles in the ME may represent a rectosigmoid pacemaker.

Electrophysiological study of the rectosigmoid canal: evidence of a rectosigmoid sphincter

Previous studies strongly suggest the presence of a sphincter at the rectosigmoid junction, an area with a mean length of 2.8 cm in adults, called the rectosigmoid canal (RSC). To find supporting evidence of a sphincteric function for the RSC, two recording electrodes were applied to each of the sigmoid colon (SC), RSC and rectum (R) in 11 subjects during operative repair of huge incisional hernias. The RSC, SC and R were individually stimulated by a further electrode and their pressures monitored by a three-channel microtip catheter. The variables of the slow waves or pacesetter potentials, recorded at rest from the RSC and R, were significantly higher than those of the SC. While the frequency and conduction velocity of pacesetter potentials of the RSC and R were similar, the potential pacesetter amplitude of the RSC was significantly higher. The increase of the electrical activity and pressure upon electrostimulation was significantly greater in the RSC than that of the SC or R. Electrostimulation led to an increase in pressure of all three areas, the RSC increase being significantly the greatest. The greater increase of the electrical activity and pressure of the rectosigmoid canal upon electrostimulation, compared to that of the SC or R, strongly supports the presence of a rectosigmoid sphincter.

Transmission of rectal electric waves: is it through circular or longitudinal smooth muscle layers or both?

The rectum possesses electric activity in the form of pacesetter (PPs) and action potentials (APs). In recent studies we suggested that the waves are not initiated by the extrarectal autonomic innervation but might be triggered by a 'rectosigmoid pacemaker' and are transmitted in the rectal wall through the rectal musculature and not the enteric nerve plexus. To investigate whether the rectal waves are transmitted through the circular or longitudinal muscle layer, the rectum of 18 mongrel dogs was exposed under anesthesia through an abdominal incision. Three electrodes were applied to the rectal wall (longitudinal muscle layer) and another 3 electrodes to the circular muscle; the latter was exposed by splitting apart the fibers of the longitudinal muscle. Rectal electric activity and pressure were recorded from the 6 electrodes before and after performing individual myotomy of the rectal longitudinal (9 dogs), circular (9 dogs), and then the whole muscle layers (18 dogs). The myotomy was performed proximal to and between the electrodes. Pacesetter (PPs) and action potentials (APs) were recorded from the 3 electrodes on the longitudinal muscle but no waves were registered from those on the circular muscle. After longitudinal muscle myotomy was performed between electrodes 1 and 2, PPs and APs were recorded from electrode 1 but not 2 and 3 and when performed proximally to electrode 1, no waves were registered. The rectal pressure increased concomitantly with occurrence of APs. Circular muscle myotomy effected no change in the rectal electric activity recorded from the 3 electrodes applied to the longitudinal muscle. In total muscle myotomy, the electric waves were recorded from the electrodes proximal but not distal to the myotomy. We propose that the motile activity of the rectal longitudinal muscle is initiated by the electric activity which appears to be triggered by the rectosigmoid pacemaker, while that of the circular muscle fibers is believed to be initiated by the stretch reflex induced by rectal distension. This concept is evidenced not only by the current findings but also by the histologic structure of the rectal musculature being of the unitary type of smooth muscles.

Effect of sigmoid colon distension on the rectosigmoid junction. Description of the rectosigmoid junction tightening reflex and its clinical implications

PURPOSE

The sigmoid colon (SC) is the site of stool storage. The stools accumulate in the SC until, at a certain volume, the mechanoreceptors in the SC wall are stimulated, evoking the sigmoidorectal junction inhibitory reflex with a resulting SC contraction, rectosigmoid junction (RSJ) relaxation and passage of the stools to the rectum. However, the RSJ status during stool accumulation in the SC has been scarcely addressed in the literature. The current study investigated this point.

METHODS

A balloon-ended tube was introduced into the SC of 21 healthy volunteers [mean age (+/- SD) 36.8 +/- 10.3 years; 15 men and 6 women]. The pressures in the SC and RSJ were measured by means of a perfused tube, at rest and during balloon inflation with carbon dioxide at two rates: slow (3 ml/min) and rapid (150 ml/min). The tests were repeated after individual anesthetization of the SC and RSJ.

RESULTS

During slow SC distension up to 80 ml included, the RSJ pressure progressively increased while the SC exhibited no pressure response (p > 0.05). At a distending volume of 100 ml, the pressure in the SC rose (p < 0. 01) and declined in the RSJ (p < 0.05), and the balloon was dispelled to the rectum. Rapid SC distension up to 40 ml included, effected no SC pressure response (p > 0.05) while the RSJ showed progressive pressure elevation. At 60 ml distension, the SC recorded a pressure rise (p < 0.001) and the RSJ a pressure decrease (p < 0. 05); the balloon was dispelled to the rectum. The pressure in the RSJ did not respond to distension of the anesthetized SC.

CONCLUSION

The study has shown that, during accumulation of stools in the SC, leakage to the rectum seems to be prevented by a reflex action which we call 'rectosigmoid junction tightening reflex'. This reflex probably acts to control both storage and emptying of the SC contents. Reflex dysfunction might lead to defecation disorders. We suggest that the RSJ tightening reflex be included as an investigative tool in the diagnosis of defecation disorders.

Study of the effect of colonic mass movements on the rectosigmoid junction with evidence of colo-rectosigmoid junction reflex

Mass movements of the left-sided colon bring the colonic material contained in it to the sigmoid colon. The cause why the colonic contents do not pass directly to the rectum but stop short of the rectosigmoid junction (RSJ) was studied. The study comprised 10 healthy volunteers (mean age 39.2 +/- 10.2 years; 8 men, 2 women). A condomended tube was introduced into the descending colon (DC) per anum. The pressure response of the DC, sigmoid colon (SC), and RSJ to condom inflation with carbon dioxide (CO2) in increments of 10 ml was recorded by means of a three-channel microtip catheter. The responses were registered upon inflation of the upper, middle, and lower third of the DC. The test was repeated after individual anesthetization of the descending colon and the RSJ on separate days. Colonic distension with 10 and 20 ml CO2 produced no significant pressure changes in the DC, SC, and RSJ (p > .05); 30 ml distension effected a pressure rise in both the DC (p < .01) and RSJ (p < .05), but no change in the SC pressure (p > .05); and 40, 50, and 60 ml distension produced pressure changes similar to those obtained with 30 ml distension. The RSJ pressure responded to distension of the saline-injected but not of the anesthetized DC. Thus, the RSJ response to colonic distension affirms the hypothesis of the possible involvement of a reflex, which we term colo-RSJ reflex. This reflex seems to regulate the passage of stools from the colon to the rectum. Further studies are required to investigate its role in the diagnosis of defecation disorders.

Role of the calices in urine flow with characterization of a caliceopelvic sphincter and reflex

AIM

To study the role of the caliceal system in urine flow.

METHODS

Eight patients (6 men, 2 women; mean age 42.6 +/- 7.6 years) with an upper polar renal mass (6 renal cysts; 2 hypernephromas) which did not encroach on the pelvicaliceal system were studied. After mass removal, a manometric catheter was introduced into one of the intact calices. Another catheter was introduced through the same calix, and the calix was filled with saline in increments of 0.1 ml, and the caliceal, caliceopelvic junction (CPJ), and renal pelvis pressures were recorded. The catheter was moved to the renal pelvis, and the pressure response of the aforementioned sites to renal pelvic filling with saline in increments of 1 ml was registered. The effect of filling of the locally anesthetized calix on the pelvicaliceal pressure was also determined.

RESULTS

Caliceal filling resulted in a rise of the caliceal (p < 0.01) and a drop of the CPJ (p < 0.01) pressures with no pressure response in the renal pelvis. Renal pelvic filling produced a rise of renal pelvic (p < 0.01) and CPJ (p < 0.05) pressures; the caliceal pressure showed no change (p > 0.05). Filling of the anesthetized calix or renal pelvis produced no significant pressure changes in calix, CPJ, or renal pelvis (p > 0. 05).

CONCLUSIONS

The CPJ dilatation upon caliceal contraction suggests a reflex relationship which we named 'caliceopelvic inhibitory reflex'. The reflex is suggested to effect caliceal evacuation. On the other hand, CPJ closure upon renal pelvic contraction postulates another reflex relationship which we designated 'pelvicaliceal excitatory reflex'. This reflex seems to prevent pelvicaliceal reflux. It is suggested that a 'functional' sphincter exists at the CPJ.

Rectal pacing: pacing parameters required for rectal evacuation of normal and constipated subjects

BACKGROUND AND PURPOSE

Our previous studies have demonstrated that rectal electric waves start at the rectosigmoid junction (RSJ) and spread caudad along the rectum. A rectosigmoid pacemaker was postulated to exist at the RSJ. We also demonstrated that electric waves in rectal inertia are so scarce that a "silent" electrorectogram is recorded; the myoelectric activity in such cases was stimulated by an artificial pacemaker placed at the RSJ. For this article we investigated the pacing parameters necessary for rectal evacuation in rectal inertia patients.

METHODS

The study comprised 24 patients with rectal inertia divided into two groups: study group (10 women, 6 men; mean age, 38.9 +/- 10.6 years) and control group (6 women, 2 men; mean age, 36.3 +/- 9.8 years). The main complaint was infrequent defecation and straining at stools. Eight healthy volunteers (6 women, 2 men; mean age, 37.2 +/- 9.4 years) with normal stool frequency were included in the study. Through a sigmoidoscope, an electrode was hooked to the RSJ (stimulating) and two electrodes were hooked to the rectal mucosa (recording). Rectal electric activity was recorded before (basal activity) and during electric stimulation of the RSJ electrode with an electrical stimulator delivering constant electric current of 5-mA amplitude and 200-ms pulse width.

RESULTS

In the healthy volunteers, rectal pacing effected increases in frequency, amplitude, and velocity from a mean of 2.3 +/- 0.9 to 6.2 +/- 1.8 cycles/min (P < 0.01), 1.2 +/- 0.6 to 1.7 +/- 0.8 mV (P < 0.05), and 4.1 +/- 1. 2 to 6.3 +/- 1.7 cm/s (P < 0.05), respectively. No waves were recorded from rectal inertia patients at rest. Rectal pacing of the study group showed pacesetter potentials with a mean frequency of 2. 1 +/- 1.2 cycles/min, amplitude of 0.9 +/- 0.1 mV, and velocity of 3. 3 +/- 1.6 ms. The control group, in whom the pacemaker was not activated, showed no electric activity.

CONCLUSIONS

Rectal pacing succeeded in producing myoelectric activity in patients with rectal inertia. It is therefore suggested that this method be applied for rectal evacuation in patients with inertia constipation.

Proceedings of the American Urogynecologic Society Multidisciplinary Symposium on Defecatory Disorders

The Multidisciplinary Symposium on Defecatory Disorders was created to delineate the breadth of defecatory disorders and propose investigations to address identified knowledge deficits. Seven experts in defecatory disorders and 24 members of the American Urogynecologic Society were invited. The experts provided brief summaries of the scope of defecatory disorders from the perspectives of their specialties. The group then divided into 3 subgroups that focused on pathophysiology, imaging, and evaluation and treatment. Defecatory disorders, including anal incontinence and constipation, are common among women of all ages. Determination of their prevalence is complicated by a lack of standardized definitions. Defecatory disorders carry lengthy differential diagnoses. Imaging studies and anorectal testing, although not standardized, can aid in distinguishing different causes of dysfunction. The lack of uniformity in diagnosis and evaluation compromises comparisons of different treatments. Standardization of diagnoses and diagnostic modalities is essential to the design of meaningful evaluations of treatments for defecatory disorders.

A study of the effect of distension of the rectosigmoid junction on the rectum and anal canal with evidence of a rectosigmoid-rectal reflex

PURPOSE

To elucidate the role of the rectosigmoid junction (RSJ) in the mechanism of defecation.

METHOD

Fourteen healthy volunteers were enrolled in the study (10 men, 4 women; mean age 38.2 +/- 10.6 years). The pressures in the rectum, anal canal, and RSJ as well as rectal balloon expulsion were recorded in response to balloon distension of the RSJ in increments of 10 ml of carbon dioxide (CO2) to 50 ml. The experiments were repeated after individual anesthetization of the RSJ, rectum, and anal canal. The expulsion of a 50-ml distended balloon located in the anesthetized rectum was tested.

RESULTS

RSJ distension with 10 ml of CO2 produced no significant pressure changes in the RSJ, rectum, or anal canal. A 20-ml distension effected a significant pressure rise in the RSJ (P < 0.05) and the rectum (P < 0.01) and a decline in the anal canal (P < 0.05); the rectal balloon was expelled to the exterior. Similar pressure changes (P > 0.05) were recorded with a 30-, 40-, and 50-ml balloon distension. The mean latency for the RSJ response was 12.6 +/- 2.2 ms and for the rectum 15.8 +/- 2.6 ms. The balloon, distended with 50 ml of CO2 and located in the rectum, was not expelled to the exterior. Balloon expulsion occurred only with distension with volumes of above 80 ml. Individual anesthetization of the RSJ, rectum, and anal canal followed by RSJ distension produced no significant pressure changes in RSJ, rectum, and anal canal as well as no rectal balloon expulsion.

CONCLUSION

The rectal contraction upon RSJ distension affirms the hypothesis of the possible involvement of a reflex, which we term "rectosigmoid-rectal reflex." This reflex relationship is evidenced by reproducibility and its absence on anesthetization of either the RSJ or the rectum, both presumably representing the two arms of the reflex arc. It is postulated that stools passing from the sigmoid colon to the rectum distend the RSJ and evoke the rectosigmoid-rectal reflex, which produces rectal contraction. The role of the reflex in defecation disorders needs to be studied.

Study of the effect of external urethral sphincter contraction on the mechanical activity of the ureterovesical junction and urinary bladder: recognition of the sphinctero-ureterovesical reflex

OBJECTIVES

To study the effect of external urethral sphincter (EUS) contraction on the urinary bladder and ureterovesical junction (UVJ).

METHODS

The study was comprised of 9 healthy volunteers (7 men, 2 women; mean age 40.8 +/- 6.6 years). A manometric catheter was introduced into each of the two UVJs and urinary bladder. The EUS was made to contract by voluntary squeezing and by electromyographic stimulation with a needle electrode inserted into the sphincter. The response of the bladder and the UVJs to EUS contraction was determined before and after anesthetization of the EUS, bladder, and the two UVJs, each at a different time.

RESULTS

On voluntary squeezing or electromyographic needle stimulation of the EUS, the pressure in both the UVJs and the urinary bladder showed a significant drop (P < 0.05 in both instances). There was no pressure response in the UVJs or in the urinary bladder 10 minutes after separate anesthetization of either the EUS or the UVJs and the bladder; however, 2 hours later, the pressure response was similar to that before anesthesia (P > 0.05).

CONCLUSIONS

Bladder and UVJ relaxation on EUS contraction postulate a reflex relationship that was reproducible and absent on anesthetization of either of the suggested two arms of the reflex: the EUS on one end and the bladder and UVJs on the other end. We call this reflex the "sphinctero-ureterovesical reflex." Further studies are needed to evaluate the possible role of this reflex in the micturition mechanism and disorders.