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)     

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.     

German Artificial Sphincter System--GASS. Development and in vitro evaluation of a novel, fully-implantable, highly integrated sphincter prosthesis for therapy of high-grade fecal incontinence]

No highly integrated sphincter prosthesis for therapy of major fecal incontinence exists. Therefore, we developed a novel neosphincter, made of polyurethane. The GASS consists of a support ring (SR) which includes a fluid reservoir, fixed on the outer diameter of the SR, and a multi-chamber occluding cuff (C(int)) on the inside diameter. The total inflation volume of C(int) is about 23 cc. The integrated micropump based on piezotechnology measures 30x13x1 mm3 (flowrate 1.4 cc/min, max. backpressure 40,000 Pa) . GASS was evaluated around the external sphincter of isolated porcine anal canals. The threshold of continence was defined as the inflating volume which water ceased to leak through the area occluded by C(int) under an induced rectal pressure of 150 cm H2O. Minimal filling volumes maintained continence for liquids against high luminal pressures. A low intraanal resting pressure (delta p(anal)) induced by activated GASS indicates a little risk of ischemic injury of the anal canal in vivo (median delta p(anal) 24.1 mm hg:15 cc vs 46.9 mm hg:21 cc). In summary, a highly integrated and efficient high-tech neosphincter for the therapy of major fecal incontinence could be realized.     

Biofeedback in treatment of urinary incontinence in stroke patients

Urinary incontinence can occur poststroke owing to weakness or incoordination of sphincter muscles, impaired bladder sensation, or hyperreflexic, neurogenic bladder. Four male subjects who had urinary incontinence associated with a stroke that had occurred 8 months to 10 years earlier, and who averaged 1.6 to 7.5 accidental voidings per week, participated in an outpatient study with a 4-week scheduled-voiding baseline, 2 to 5 sessions of biofeedback-assisted bladder retraining, and 6- to 12-month follow-up. Training sessions included stepwise filling of the bladder and manometric feedback display of bladder pressure, abdominal pressure, and external anal sphincter pressure. Training procedures were designed to teach subjects to attend to bladder sensations, inhibit bladder contractions, and improve voluntary sphincter muscle control. All four subjects achieved and maintained continence regardless of substantial differences in subject characteristics, including laterality of stroke, degree of sensory impairment, and independence in daily activities.     

Sphincter incontinence: Is regenerative medicine the best alternative to restore urinary or anal sphincter function?

Incontinence is a major public health concern in aging societies. It is caused by age-dependent spontaneous apoptosis of muscle cells in the urinary and fecal sphincters, and is aggravated in women due to birth trauma. Compared to other currently employed invasive surgical management techniques associated with morbidity and recurrence, replacement or regeneration of dysfunctional sphincter through stem cell therapy and tissue engineering techniques hold great promise. This review focuses on the pathophysiological analysis of urinary incontinence and the possible application of muscle-derived-stem cells, satellite cells, chondrocytes and adipose-derived-stem cells in restoring sphincter functions.     

Biofeedback in treatment of urinary incontinence in stroke patients

Urinary incontinence can occur poststroke owing to weakness or incoordination of sphincter muscles, impaired bladder sensation, or hyperreflexic, neurogenic bladder. Four male subjects who had urinary incontinence associated with a stroke that had occurred 8 months to 10 years earlier, and who averaged 1.6 to 7.5 accidental voidings per week, participated in an outpatient study with a 4-week scheduled-voiding baseline, 2 to 5 sessions of biofeedback-assisted bladder retraining, and 6- to 12-month follow-up. Training sessions included stepwise filling of the bladder and manometric feedback display of bladder pressure, abdominal pressure, and external anal sphincter pressure. Training procedures were designed to teach subjects to attend to bladder sensations, inhibit bladder contractions, and improve voluntary sphincter muscle control. All four subjects achieved and maintained continence regardless of substantial differences in subject characteristics, including laterality of stroke, degree of sensory impairment, and independence in daily activities.     

A components analysis of biofeedback in the treatment of fecal incontinence

Fecal incontinence is a socially disabling symptom for which rectosphincteric biofeedback has been reported to be dramatically effective. The most commonly employed biofeedback procedure incorporates three separate and potentially effective components: (1) exercise of the external sphincter muscle, (2) training in discrimination of rectal sensations, and (3) training synchrony of the internal and external sphincter responses. This paper reports the results of single case experiments employed with eight incontinent patients to examine the contributions of each of these components. All eight patients improved, but only one required the biofeedback procedure as it was originally described. Three responded to sensory discrimination training, one to exercise training, and one to the training of synchronous sphincteric responses; three recovered independently of the effects of biofeedback. Despite the achievement of continence, the rectosphincteric reflexes following treatment continued to be abnormal in every case. These findings suggest that the character of the external sphincter response to rectal distension is an unreliable index of sphincter function and that exercise and sensory discrimination training procedures are effective for some cases of fecal incontinence.The work described in this paper was supported by Grant No. MA 6241 from the Medical Research Council of Canada.     

Electromyographic study of the anal sphincter in women

The objectives of this study were to identify the electromyographic (EMG) changes in the anal sphincters, and to determine whether there are myogenic or neurogenic damages to the muscles in stress incontinence in women (SI). Possible damage was expected while the number of EMG studies has reported evidence of denervation as a result of certain aethiologic factors. The intention was to determine risk factors for development of fecal incontinence. 110 women with SI and 91 women with spinal lesion (SL) were examined. The anal sphincters were examined in both groups by means of standarized EMG technique with concentric needle electrode. The results demonstrated predominatly neurogenic lesion of the anal sphincters in SL women and predominatly normal findings in SI women. The contribution of genitourinary or pelvic surgeries to the fecal incontinence in SI group has been established by means of discriminatory analysis.     

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.     

Distribution of interstitial cells of Cajal in tunica muscularis of the canine rectoanal region

Electrical and mechanical activity of the circular muscle layer in the rectoanal region of the gastrointestinal tract undergoes considerable changes in the site of dominant pacemaking activity, frequency, and waveform shape. The present study was performed to determine whether changes in the structural organization of the circular layer or in the density, distribution, and ultrastructure of interstitial cells of Cajal (ICC) could account for this heterogeneity in electrical and mechanical activities. Light microscopy revealed that the structural organization of the circular muscle layer underwent dramatic morphological changes, from a tightly packed layer with poorly defined septa in the proximal rectum to one of discrete muscle bundles separated by large septae in the internal anal sphincter. Kit immunohistochemistry revealed a dense network of ICC along the submucosal and myenteric borders in the rectum, whereas in the internal anal sphincter, ICC were located along the periphery of muscle bundles within the circular layer. Changes in electrical activity within the circular muscle layer can be partially explained by changes in the structure of the muscle layer and changes in the distribution of ICC in the rectoanal region of the gastrointestinal tract.     

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.     

Interstitial cell network volume is reduced in the terminal bowel of ageing mice

Ageing is associated with impaired neuromuscular function of the terminal gastrointestinal (GI) tract, which can result in chronic constipation, faecal impaction and incontinence. Interstitial cells of cajal (ICC) play an important role in regulation of intestinal smooth muscle contraction. However, changes in ICC volume with age in the terminal GI tract (the anal canal including the anal sphincter region and rectum) have not been studied. Here, the distribution, morphology and network volume of ICC in the terminal GI tract of 3‐ to 4‐month‐old and 26‐ to 28‐month‐old C57BL/6 mice were investigated. ICC were identified by immunofluorescence labelling of wholemount preparations with an antibody against c‐Kit. ICC network volume was measured by software‐based 3D volume rendering of confocal Z stacks. A significant reduction in ICC network volume per unit volume of muscle was measured in aged animals. No age‐associated change in ICC morphology was detected. The thickness of the circular muscle layer of the anal sphincter region and rectum increased with age, while that in the distal colon decreased. These results suggest that ageing is associated with a reduction in the network volume of ICC in the terminal GI tract, which may influence the normal function of these regions.     

Dynamic rectus abdominis muscle sphincter for stoma continence: an acute functional study in a dog model

Fecal stomal incontinence is a problem that continues to defy surgical treatment. Previous attempts to create continent stomas using dynamic myoplasty have had limited success due to denervation atrophy of the muscle flap used in the creation of the sphincter and because of muscle fatigue resulting from continuous electrical stimulation. To address the problem of denervation atrophy, a stomal sphincter was designed using the most caudal segment of the rectus abdominis muscle, preserving its intercostal innervation as well as its vascular supply. The purpose of the present study was to determine whether this rectus abdominis muscle island flap sphincter design could maintain stomal continence acutely. In this experiment, six dogs were used to create eight rectus abdominis island flap stoma sphincters around a segment of distal ileum. Initially, the intraluminal stomal pressures generated by the sphincter using different stimulation frequencies were determined. The ability of this stomal sphincter to generate continence at different intraluminal bowel pressures was then assessed. In all cases, the rectus abdominis muscle sphincter generated peak pressures well above those needed to maintain stomal continence (60 mmHg). In addition, each sphincter was able to maintain stomal continence at all intraluminal bowel pressures tested.     

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.     

Comparative and functional morphology of musculus canalis ani in tetrapod mammals and primates]

Comparative anatomy of structure and function of the M. canalis ani in tetrapode mammals and primates is described for the first time. The muscle itself lies on the sphincter ani internus in the area between the anorectal ("pectinate") and anocutaneal ("white") lines and its circumference is intact around the entire anal canal. The canalis ani muscle orginates from the superior part of the sphincter ani internus and concomitantly receives additional fibers from the longitudinal muscle. Caudally the muscle dips back into the sphincter ani internus and, at the same time, a small portion of the fibers go to the longitudinal muscle and, likewise, a portion also sets itself on the perinaal skin. On the basis of its morphological relationship to the convoluted vessels of the rectal venous plexus, the canalis ani muscle appears to be able to complete the closing of the anus in the continence phase to such an extent that a complete closing of the anal lumen is guaranted.     

Bending continuous structures with SMAs: a novel robotic fish design

In this paper, we describe our research on bio-inspired locomotion systems using deformable structures and smart materials, concretely shape memory alloys (SMAs). These types of materials allow us to explore the possibility of building motor-less and gear-less robots. A swimming underwater fish-like robot has been developed whose movements are generated using SMAs. These actuators are suitable for bending the continuous backbone of the fish, which in turn causes a change in the curvature of the body. This type of structural arrangement is inspired by fish red muscles, which are mainly recruited during steady swimming for the bending of a flexible but nearly incompressible structure such as the fishbone. This paper reviews the design process of these bio-inspired structures, from the motivations and physiological inspiration to the mechatronics design, control and simulations, leading to actual experimental trials and results. The focus of this work is to present the mechanisms by which standard swimming patterns can be reproduced with the proposed design. Moreover, the performance of the SMA-based actuators' control in terms of actuation speed and position accuracy is also addressed.     

Bowel Dysfunction in Spinal Cord Injury: Current Perspectives

Permanent disruptions of gastrointestinal function are very common sequel of spinal cord injury (SCI). When motor and sensory nervous integrity are severely affected, neurogenic gastrointestinal dysfunction is an inevitable consequence. Autonomic nervous system miss function has significantly diminished or lost sensory sensations followed with incomplete evacuation of stool from the rectal vault, immobility, and reduced anal sphincter tone all of those predisposing to increased risk of fecal incontinence (FI). The FI is, beside paralysis of extremities, one of the symptoms most profoundly affecting quality of life (QOL) in patients with SCI. We are reviewing current perspectives in management of SCI, discussing some pathophysiology mechanisms which could be addressed and pointing toward actual practical concepts in use for evaluation and improvements necessary to sustain SCI patients QOL.     

Development of a three-dimensional physiological model of the internal anal sphincter bioengineered in vitro from isolated smooth muscle cells

Fecal incontinence affects people of all ages and social backgrounds and can have devastating psychological and economic consequences. This disorder is largely attributed to decreased mechanical efficiency of the internal anal sphincter (IAS), yet little is known about the pathophysiological mechanisms responsible for the malfunction of sphincteric smooth muscle at the cellular level. The object of this study was to develop a three-dimensional (3-D) physiological model of the IAS bioengineered in vitro from isolated smooth muscle cells. Smooth muscle cells isolated from the IAS of rabbits were seeded in culture on top of a loose fibrin gel, where they migrated and self-assembled in circumferential alignment. As the cells proliferated, the fibrin gel contracted around a 5-mm-diameter SYLGARD mold, resulting in a 3-D cylindrical ring of sphincteric tissue. We found that 1) the bioengineered IAS rings generated a spontaneous basal tone, 2) stimulation with 8-bromo-cAMP (8-Br-cAMP) caused a sustained decrease in the basal tone (relaxation) that was calcium-independent, 3) upon stimulation with ACh, bioengineered IAS rings showed a calcium- and concentration-dependent peak contraction at 30 s that was sustained for 4 min, 4) addition of 8-Br-cAMP induced rapid relaxation of ACh-induced contraction and force generation of IAS rings, and 5) bioengineered sphincter rings show striking functional differences when compared with bioengineered rings made from isolated colonic smooth muscle cells. This is the first report of a 3-D in vitro model of a gastrointestinal smooth muscle IAS. Bioengineered IAS rings demonstrate physiological functionality and may be used in the elucidation of the mechanisms causing sphincter malfunction.