The internal anal sphincter: mechanisms of control and its role in maintaining anal continence

Parachute-like pull-through anastomosis for low rectal cancer: a new method for preservation of anal function

BACKGROUND

With recent improvements in surgical technique, oncological outcomes of low rectal cancer have improved over time. But the QoL impairment as a result of anal functional disorder cannot be ignored. And the incidence of anastomosis-related complications cannot be ignored. To address these problems, a personal technique for pull-through coloanal anastomosis (parachute-like intussuscept pull-through anastomosis) was introduced and evaluated. This technique can relatively reduce surgical complications, minimize the impact of anal function, and obviate a colostomy creation.

METHODS

Between June 2020 and April 2021, 14 consecutive patients with rectal cancer underwent laparoscopic-assisted resection of rectal cancer in our hospital. Parachute-like pull-through anastomosis method was performed in all patients. Anal function, perioperative details, and postoperative outcomes were analyzed.

RESULTS

The mean (SD) operative time of first stage was 282.1 min (range 220-370) with an average estimated blood loss of 90.3 mL (range 33-200). And the mean (SD) operative time of second was 46 min (range 25-76) with an average estimated blood loss of 16.1 mL (range 5-50). Wexner scores declined significantly during the median follow-up of 18 months. Four postoperative anastomosis-related complications occurred in 14 patients, including perianastomotic abscess: 1 case (7%), anastomotic stricture: 1 case (7%), and colonic ischemia of the exteriorized colonic segment: 2 cases (14%).

CONCLUSION

The results suggest that the method can facilitate safe and easy completion of coloanal anastomosis, using parachute-like pull-through anastomosis, with acceptable anal function.

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

BACKGROUND

Anorectal manometry (ARM) comprehensively assesses anorectal sensorimotor functions.

PURPOSE

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.

Is pelvic floor muscle contractility an important factor in anal incontinence?

OBJECTIVE

Pelvic floor muscle contractility (PFMC) may contribute to anal continence. The aim of this study was to assess the association between clinical and sonographic measures of PFMC and anal incontinence (AI) symptoms, after controlling for anal sphincter and levator ani muscle (LAM) trauma.

METHODS

This was a retrospective study of 1383 women assessed at a tertiary center between 2013 and 2016. All patients underwent an interview, including the St Mark's incontinence score (SMIS) in those who reported AI symptoms, a clinical examination, including assessment of PFMC using the modified Oxford scale (MOS), and four-dimensional translabial ultrasound (TLUS). Sonographic measures of PFMC, i.e. cranioventral shift of the bladder neck (BN) and reduction of anteroposterior (AP) diameter of the levator hiatus, were measured offline using ultrasound volumes obtained at rest and on maximum pelvic floor contraction. The reviewer was blinded to all clinical data.

RESULTS

Of the 1383 patients assessed during the study period, seven were excluded due to missing imaging data, leaving 1376 for analysis. Mean age of the participating women was 55 years and mean body mass index was 29 kg/m² . AI was reported by 221 (16.1%) women, with a mean SMIS of 11.8. Mean MOS grade was 2.3. On TLUS, mean BN cranioventral shift was 5.9 mm and mean AP diameter reduction was 8.1 mm. LAM avulsion and significant external anal sphincter (EAS) defect were diagnosed in 24.8% and 8.7% patients, respectively. On univariate analysis, sonographic measures of PFMC were not associated with AI. Lower MOS grade was associated with symptoms of AI; however, statistical significance was lost on multivariate analysis.

CONCLUSION

Clinical and sonographic measures of PFMC were not significantly associated with AI symptoms after controlling for EAS and LAM trauma. © 2020 International Society of Ultrasound in Obstetrics and Gynecology.

Bionic measurement of defecation in a swine model

OBJECTIVE

Fecobionics was used to assess pressures, orientation, bending, shape, and cross-sectional area (CSA) changes during defecation. This study aimed to evaluate the device feasibility and performance in swine.

APPROACH

Twelve pigs had wired or wireless Fecobionics devices inserted in the rectum. The bag was distended to simulate feces in the rectum. Fecobionics data were acquired simultaneously during the whole experiment. Six pigs were euthanized immediately after the procedure for evaluation of acute injury to anorectum (acute group). The remaining pigs lived two weeks before euthanasia for evaluation of long-term tissue damage and inflammation (chronic group). Signs of discomfort were monitored.

MAIN RESULTS

All animals tolerated the experiment well. The chronic animals showed normal behavior after the procedure. Mucosal damage, bleeding, or inflammation was not found in either group. Fecobionics was defecated 1 min 35 s-61 min 0 s (median 8 min 58 s) after insertion. The defecation lasted 0 min 20 s-4 min 25 s (median 1 min 52 s). The device was almost straight inside rectum (160°-180°) but usually bended 5°-20° during contractions. The three pressure sensors showed simultaneous and identical increase during rectal or abdominal muscle contractions, indicating the location inside rectum. During defecation, the maximum rear pressure was 114.1 ± 14.3 cmH₂O whereas the front pressure gradually decreased to 0 cmH₂O, indicating the front passed anus. CSA decreased from 1017.1 ± 191.0 mm² to 530.7 ± 46.5 mm² when the probe passed from the rectum through the anal canal.

SIGNIFICANCE

Fecobionics provides defecatory measurements under physiological conditions in pigs without inducing tissue damage.

Variation in rectoanal inhibitory reflex after laparoscopic intersphincteric resection for ultralow rectal cancer

AIM

The aim was to evaluate the physiological variation in rectoanal inhibitory reflex (RAIR) after laparoscopic intersphincteric resection (Lap-ISR) for ultralow rectal cancer.

METHOD

This was a retrospective study that included 56 patients who underwent Lap-ISR from a prospectively collected database. The RAIR was examined preoperatively and up to 12 months after ileostomy closure. The primary outcome included physiological variation in RAIR and its difference between partial, subtotal and total ISR. The secondary outcome was its correlation with functional outcome.

RESULTS

The reflex was present in 95% (53/56) of patients preoperatively, in 36% (20/56) before ileostomy closure, in 48% (27/56) at 3-6 months and in 61% (34/56) at 12 months after ileostomy closure. The elicited volume of RAIR was significantly increased at 12 months after ileostomy closure than at baseline (P = 0.005), but its duration and amplitude did not differ significantly. There was no significant difference in the reflex recovery between the ISR groups (partial vs. subtotal vs. total: 65% vs. 63% vs. 44%, P = 0.61). At 12 months after ileostomy closure, the RAIR-present group had favourable functional results and patient satisfaction (P < 0.05). Major faecal incontinence was found in 82% of patients in the RAIR-absent group.

CONCLUSION

The RAIR is abolished in the majority of patients after Lap-ISR, but a time-dependent recovery could be observed in more than half of the patients. The reflex recovery is not influenced by the resection grade of the internal sphincter. However, persistent loss of the RAIR correlates with worse continence.

Japanese Practice Guidelines for Fecal Incontinence Part 2-Examination and Conservative Treatment for Fecal Incontinence- English Version

Examination for fecal incontinence is performed in order to evaluate the condition of each patient. As there is no single method that perfectly assesses this condition, there are several tests that need to be conducted. These are as follows: anal manometry, recto anal sensitivity test, pudendal nerve terminal motor latency, electromyogram, anal endosonography, pelvic magnetic resonance imaging (MRI) scan, and defecography. In addition, the mental and physical stress most patients experience during all these examinations needs to be taken into consideration. Although some of these examinations mostly apply for patients with constipation, we hereby describe these tests as tools for the assessment of fecal incontinence. Conservative therapies for fecal incontinence include diet, lifestyle, and bowel habit modification, pharmacotherapy, pelvic floor muscle training, biofeedback therapy, anal insert device, trans anal irrigation, and so on. These interventions have been identified to improve the symptoms of fecal incontinence by determining the mechanisms resulting in firmer stool consistency; strengthening the pelvic floor muscles, including the external anal sphincter; normalizing the rectal sensation; or periodic emptying of the colon and rectum. Among these interventions, diet, lifestyle, and bowel habit modifications and pharmacotherapy can be performed with some degree of knowledge and experience. These two therapies, therefore, can be conducted by all physicians, including general practitioners and other physicians not specializing in fecal incontinence. However, patients with fecal incontinence who did not improve following these initial therapies should be referred to specialized institutions. Contrary to the initial therapies, specialized therapies, including pelvic floor muscle training, biofeedback therapy, anal insert device, and trans anal irrigation, should be conducted in specialized institutions as these require patient education and instructions based on expert knowledge and experience. In general, conservative therapies should be performed for fecal incontinence before surgery because its pathophysiologies are mostly attributed to benign conditions. All Japanese healthcare professionals who take care of patients with fecal incontinence are expected to understand the characteristics of each conservative therapy, so that appropriate therapies will be selected and performed. Therefore, in this chapter, the characteristics of each conservative therapy for fecal incontinence are described.

Disproportionality analysis in VigiBase as a drug repositioning method for the discovery of potentially useful drugs in Alzheimer's disease

Drug repositioning aims to propose new indications for marketed drugs. Although several methods exist, the utility of pharmacovigilance databases for this purpose is unclear. We conducted a disproportionality analysis in the World Health Organization pharmacovigilance database VigiBase to identify potential anticholinesterase drug candidates for repositioning in Alzheimer's disease (AD).

METHODS

Disproportionality analysis is a validated method for detecting significant associations between drugs and adverse events (AEs) in pharmacovigilance databases. We applied this approach in VigiBase to establish the safety profile displayed by the anticholinesterase drugs used in AD and searched the database for drugs with similar safety profiles. The detected drugs with potential activity against acetylcholinesterase and butyrylcholinesterases (BuChEs) were then evaluated to confirm their anticholinesterase potential.

RESULTS

We identified 22 drugs with safety profiles similar to AD medicines. Among these drugs, 4 (clozapine, aripiprazole, sertraline and S-duloxetine) showed a human BuChE inhibition rate of over 70% at 10^-5  M. Their human BuChE half maximal inhibitory concentration values were compatible with clinical anticholinesterase action in humans at their normal doses. The most active human BuChE inhibitor in our study was S-duloxetine, with a half maximal inhibitory concentration of 1.2 μM. Combined with its ability to inhibit serotonin (5-HT) reuptake, the use of this drug could represent a novel multitarget directed ligand therapeutic strategy for AD.

CONCLUSION

We identified 4 drugs with repositioning potential in AD using drug safety profiles derived from a pharmacovigilance database. This method could be useful for future drug repositioning efforts.

A missing distal complex of the external and internal anal sphincters: a macroscopic and histologic study using Japanese and German elderly cadavers

The lower margin of the internal anal sphincter (IAS) is considered to lie on a J-shaped, subcutaneous part (SCP) of the external anal sphincter (EAS). The lower IAS is united with the J-shaped SCP to form a smooth-striated muscle complex. In the first part of this study, we ensured the presence of the J-shaped EAS in the lateral wall of the anal canal from 12 near-term fetuses. Second, in the lateral anal wall, the examination of the longitudinal section from 20 male and 24 female Japanese cadavers (72-95 years-old) demonstrated that the J-shaped EAS was lost in 15 (34%) due to the very small SCP. Third, we demonstrated that the J-shaped EAS was restricted in the latera anal wall using longitudinal histological sections of the anal canal from 11 male Japanese cadavers (75-89 years-old). Therefore, a site-dependent difference in the IAS-EAS configuration was evident. Finally, we compared a frequency of the lost J-shape between human populations using 10 mm-thick frontal slices from 36 Japanese and 28 German cadavers. The two groups of cadavers were compatible in age (a 0.2-years' difference in males). The macroscopic observations revealed that the J-shaped EAS was absent from 13 (36%) Japanese and six (20%) German specimens, suggesting that the SCP degeneration occurred more frequent in elderly Japanese than elderly German individuals (p < 0.05). The distal IAS-EAS complex seemed to push residual feces out of the anal canal at a transient phase from evacuation to closure. The absence might be the first sigh of anal dysfunction.

Ultimate Functional Preservation With Intersphincteric Resection for Rectal Cancer

The proximity of the very low rectum rectal cancer to the anal sphincter raises a specific problem: how and until when can we preserve the anal continence without compromising the oncological result of the tumor resection? In this situation, intersphincteric resection (ISR) offers an excellent alternative to abdominoperineal resection (APR), but the selection of patients for this option must be extremely precise. This complex choice justifies the simultaneous consideration of an oncological approach with a functional approach in order to provide a full benefit to the patient. When a circumferential resection margin of at least 1 mm can be performed with a distal resection margin of at least 1 cm with or without preoperative radiotherapy, ISR ensures a safety choice. The oncological results of ISR reported in the literature when performed properly found a 5-year disease-free survival of 80.2% with a local recurrence rate of only 5.8%. In parallel to this oncological evaluation, the expected post-operative functional outcome and the resulting quality of life must be properly assessed pre-operatively, since partial or total resection of the internal sphincter impacts significantly on the functional outcome. Based on data from the literature, this work reports the essential anatomical considerations and then the oncological and functional elements indispensables when an anal continence preservation is evoked for a tumor of the very low rectum. Finally, the precise selection criteria and the major surgical principles are outlined in order to guarantee the safety of this modern choice for the patient.

Preservation of the colo-anal reflex in colonic transection and post-operative Hirschsprung's disease: Potential extrinsic neural pathway

BACKGROUND

The colo-anal reflex is a distinct reflex whereby the internal anal sphincter (IAS) relaxes in association with colonic high amplitude propagating contractions (HAPCs) in contrast to the recto-anal inhibitory reflex (RAIR), which is characterized by IAS relaxation upon rectal distension. The RAIR is mediated by the myenteric plexus and therefore absent in Hirschsprung disease. We retrospectively assessed the presence and the characteristics of the colo-anal reflex in children in whom large bowel continuity had been surgically disrupted to assess the role of the extrinsic nervous system in the reflex.

METHODS

High-resolution (HR) colonic manometry and HR-anorectal manometry were used to evaluate both colonic and anal motor activity in ten children with treatment-unresponsive slow transit constipation (STC), who had previously undergone left-sided colostomy formation with consequent disruption of the bowel continuity, and in two children with Hirschsprung's disease (HSCR), who had previously undergone distal colon resection followed by Duhamel pull-through. Eight children with STC, normal colonic motor activity, and preserved large bowel continuity served as a control group. The presence and characteristics of colo-anal reflex were analyzed.

KEY RESULTS

In the study group, all patients showed the presence of both normal HAPCs and the presence of the colo-anal reflex. In two cases of HSCR, RAIR was absent; however, both patients demonstrated a colo-anal reflex.

CONCLUSIONS

In children with disrupted continuity of the colon and/or abnormal anal reflex, the colo-anal reflex is still preserved suggesting that it is mediated by a different pathway from the RAIR, possibly an extrinsic neural pathway.

Increased anal basal pressure in chronic anal fissures may be caused by overreaction of the anal-external sphincter continence reflex

Chronic anal fissure is a painful disorder caused by linear ulcers in the distal anal mucosa. Even though it counts as one of the most common benign anorectal disorders, its precise etiology and pathophysiology remains unclear. Current thinking is that anal fissures are caused by anal trauma and pain, which leads to internal anal sphincter hypertonia. Increased anal basal pressure leads to diminished anodermal blood flow and local ischemia, which delays healing and leads to chronic anal fissure. The current treatment of choice for chronic anal fissure is either lateral internal sphincterotomy or botulinum toxin injections. In contrast to current thinking, we hypothesize that the external, rather than the internal, anal sphincter is responsible for increased anal basal pressure in patients suffering from chronic anal fissure. We think that damage to the anal mucosa leads to hypersensitivity of the contact receptors of the anal-external sphincter continence reflex, resulting in overreaction of the reflex. Overreaction causes spasm of the external anal sphincter. This in turn leads to increased anal basal pressure, diminished anodermal blood flow, and ischemia. Ischemia, finally, prevents the anal fissure from healing. Our hypothesis is supported by two findings. The first concerned a chronic anal fissure patient with increased anal basal pressure (170mmHg) who had undergone lateral sphincterotomy. Directly after the operation, while the submucosal anesthetic was still active, basal anal pressure decreased to 80mmHg. Seven hours after the operation, when the anesthetic had completely worn off, basal anal pressure increased again to 125mmHg, even though the internal anal sphincter could no longer be responsible for the increase. Second, in contrast to previous studies, recent studies demonstrated that botulinum toxin influences external anal sphincter activity and, because it is a striated muscle relaxant, it seems reasonable to presume that it affects the striated external anal sphincter, rather than the smooth internal anal sphincter. If our hypothesis is proved correct, the treatment option of lateral internal sphincterotomy should be abandoned in patients suffering from chronic anal fissures, since it fails to eliminate the cause of high anal basal pressure. Additionally, lateral internal sphincterotomy may cause damage to the anal-external sphincter continence reflex, resulting in fecal incontinence. Instead, higher doses of botulinum toxin should be administered to those patients suffering from chronic anal fissure who appeared unresponsive to lower doses.

Altered Colorectal Compliance and Anorectal Physiology in Upper and Lower Motor Neurone Spinal Injury May Explain Bowel Symptom Pattern

OBJECTIVES

Supraconal spinal cord injury (SCI) and lower motor neurone spinal cord injury (LMN-SCI) cause bowel dysfunction; colorectal compliance may further define its pathophysiology. The aim of this study was to investigate rectal (RC) and sigmoid (SC) compliance and anorectal physiology parameters, in these subjects.

METHODS

Twenty-four SCI subjects with gut symptoms (14 RC, 10 SC) and 13 LMN-SCI subjects (9 RC, 4 SC) were compared with 20 spinal intact controls (10 RC, 10 SC). Staircase distensions were performed using a barostat. Anorectal manometry, including rectoanal inhibitory reflex (RAIR) measurement, was performed in all. Data presented as mean±standard error (SCI/LMN-SCI vs. controls).

RESULTS

SCI subjects had a higher RC (17.0±1.9 vs. 10.7±0.5 ml/mm Hg, P<0.05) and SC (8.5±0.6 vs. 5.2±0.5 ml/mm Hg, P=0.002). LMN-SCI subjects had a lower RC (7.3±0.7 ml/mm Hg, P=0.0021) while SC was unchanged (8.3±2.2 ml/mm Hg, P>0.05). Anal resting pressure was decreased in SCI (55±5 vs. 79±7 cmH2O, P=0.0102). Anal squeeze pressure was decreased in LMN-SCI (76±13 vs. 154±21 cmH2O, P=0.0158). In SCI and LMN-SCI, the amplitude reduction of the RAIR was greater (62±4% and 70±6% vs. 44±3%, P=0.0007).

CONCLUSIONS

Colorectal compliance abnormalities may explain gut symptoms: increased RC and SC contributing to constipation in SCI, reduced rectal compliance contributing to fecal incontinence (FI) in LMN-SCI. Reduced resting anal pressure in SCI and reduced anal squeeze pressure in LMN-SCI along with a greater RAIR amplitude reduction may be factors in FI. These co-existing abnormalities may explain symptom overlap, and represent future therapeutic targets to ameliorate neurogenic bowel dysfunction.

How to Perform and Interpret a High-resolution Anorectal Manometry Test

High-resolution anorectal manometry (HR-ARM) and high-definition anorectal manometry (HD-ARM) catheters have closely spaced water-perfused or solid state circumferentially-oriented pressure sensors that provide much better spatiotemporal pressurization than non-high resolution catheters. This is a comprehensive review of HR-ARM and HD-ARM anorectal manometry catheter systems, the methods for conducting, analyzing, and interpreting HR-ARM and HD-ARM, and a comparison of HR-ARM with non-high resolution anorectal manometry. Compared to non-high resolution techniques, HR-ARM and HD-ARM studies take less time and are easier to interpret. However, HR-ARM and HD-ARM catheters are more expensive and fragile and have a shorter lifespan. Further studies are needed to refine our understanding of normal values and to rigorously evaluate the incremental clinical utility of HR-ARM or HD-ARM compared to non-high resolution manometry.

Relationship Among Anal Sphincter Injury, Patulous Anal Canal, and Anal Pressures in Patients With Anorectal Disorders

BACKGROUND & AIMS

The anal sphincters and puborectalis are imaged routinely with an endoanal magnetic resonance imaging (MRI) coil, which does not assess co-aptation of the anal canal at rest. By using a MRI torso coil, we identified a patulous anal canal in some patients with anorectal disorders. We aimed to evaluate the relationship between anal sphincter and puborectalis injury, a patulous anal canal, and anal pressures.

METHODS

We performed a retrospective analysis of data from 119 patients who underwent MRI and manometry analysis of anal anatomy and pressures, respectively, from February 2011 through March 2013 at the Mayo Clinic. Anal pressures were determined by high-resolution manometry, anal sphincter and puborectalis injury was determined by endoanal MRI, and anal canal integrity was determined by torso MRI. Associations between manometric and anatomic parameters were evaluated with univariate and multivariate analyses.

RESULTS

Fecal incontinence (55 patients; 46%) and constipation (36 patients; 30%) were the main indications for testing; 49 patients (41%) had a patulous anal canal, which was associated with injury to more than 1 muscle (all P ≤ .001), and internal sphincter (P < .01), but not puborectalis (P = .09) or external sphincter (P = .06), injury. Internal (P < .01) and external sphincter injury (P = .02) and a patulous canal (P < .001), but not puborectalis injury, predicted anal resting pressure. A patulous anal canal was the only significant predictor (P < .01) of the anal squeeze pressure increment.

CONCLUSIONS

Patients with anorectal disorders commonly have a patulous anal canal, which is associated with more severe anal injury and independently predicted anal resting pressure and squeeze pressure increment. It therefore is important to identify a patulous anal canal because it appears to be a marker of not only anal sphincter injury but disturbances beyond sphincter injury, such as damage to the anal cushions or anal denervation.

Anorectal incontinence: a challenge in diagnostic and therapeutic approach

Anorectal incontinence is a symptom of a complex multifactorial disorder involving the pelvic floor and anorectum, which is a severe disability and a major social problem. Various causes may affect the anatomical and functional integrity of the pelvic floor and anorectum, leading to the anorectal continence disorder and incontinence. The most common cause of anorectal incontinence is injury of the sphincter muscles following delivery or anorectal surgeries. Although the exact incidence of anorectal incontinence is unknown, various studies suggest that it affects ~2.2-8.3% of adults, with a significant prevalence in the elderly (>50%). The successful treatment of anorectal incontinence depends on the accurate diagnosis of its cause. This can be achieved by a thorough assessment of patients. The management of incontinent patients involves conservative therapeutic procedures, surgical techniques, and minimally invasive approaches.

Patterns of impaired internal anal sphincter activity in patients with anal fissure

AIM

The patterns of impaired internal anal sphincter activity were studied in patients with anal fissure (AF).

METHOD

Twenty healthy controls and 61 patients with acute AF were studied, using anorectal manometry with electromyography (EMG), and 53 patients with chronic AF using high-resolution manometry and ultrasonography. Mean and maximal resting anal pressure (MRAP), spontaneous rhythmic slow and ultraslow waves (USW) and relaxation induced by rectal distension were measured.

RESULTS

Patients with acute AF had higher mean (106.4 ± 28.1 mmHg) and maximal resting anal pressure (161.5 ± 43.7 mmHg) than those with chronic AF (P < 0.05); 95% of patients had slow waves (SW) and 67% ultraslow waves. Patients with chronic AF had higher mean (92.4 ± 22.6 mmHg) and maximal resting anal pressure (117.5 ± 32.0 mmHg) than controls and 94% of patients had slow waves and 69% ultraslow waves. Patients with ultraslow waves (with either acute or chronic AF) had increased internal sphincter hypertonicity (mean and maximal resting pressure), decreased internal sphincter relaxation and increased after-contraction following rectal distension.

CONCLUSIONS

Patients with acute AF had higher hypertonicity than those with chronic AF and both had increased spontaneous rhythmic activity (waves). Patients with AF and ultraslow waves had higher internal anal sphincter hypertonicity and reduced internal sphincter relaxation and enhanced after-contraction following rectal distension.

Topographic and manometric characterization of the recto-anal inhibitory reflex

BACKGROUND

Recto-anal inhibitory reflex (RAIR) is an integral part of normal defecation. The physiologic characteristics of RAIR along anal length and anterior-posterior axis are unknown. The aim of this study was to perform topographic and vector-graphic evaluation of RAIR along anal canal using high definition manometry (HDM), and examine the role of various muscle components.

METHODS

Anorectal topography was assessed in 10 healthy volunteers using HDM probe with 256 sensors. Recto-anal inhibitory reflex data were analyzed every mm along the length of anal canal for topographic, baseline, residual, and plateau pressures during five mean volumes of balloon inflation (15 cc, 40 cc, 71 cc, 101 cc, 177 cc), and in 3D by dividing anal canal into 4 × 2.1 mm grids.

KEY RESULTS

Relaxation pressure progressively increases along anal canal with increasing balloon volume up to 71 cc and thereafter plateaus. In 3D, RAIR is maximally seen at the middle and upper portions of anal canal (levels 1.2-3.2 cm) and posteriorly. Peak residual pressure was seen at proximal anal canal.

CONCLUSIONS & INFERENCES

Recto-anal inhibitory reflex is characterized by differential anal relaxation along anterior-posterior axis, longitudinally along the length of anal canal, and it depends on the rectal distention volume. It is maximally seen at internal anal sphincter pressure zone. Multidimensional analyses indicate that external anal sphincter provides bulk of anal residual pressure. Our findings emphasize importance of sensor location and orientation; as anterior and more distal location may miss RAIR.

Total mesorectal excision with intraoperative assessment of internal anal sphincter innervation provides new insights into neurogenic incontinence

BACKGROUND

The aim of this prospective study was to assess internal anal sphincter (IAS) innervation in patients undergoing total mesorectal excision (TME) by intraoperative neuromonitoring (IONM).

STUDY DESIGN

Fourteen patients underwent TME. IONM was carried out through pelvic splanchnic nerve stimulation under continuous electromyography of the IAS. Anorectal function was assessed with the digital rectal examination scoring system and a standardized questionnaire.

RESULTS

Nine of 11 patients who underwent low anterior resection had positive IONM results, with stimulation-induced increased IAS electromyographic amplitudes (median 0.23 μV (interquartile range [IQR] 0.05, 0.56) vs median 0.89 μV (IQR 0.64, 1.88), p < 0.001) after TME. The patients with the positive IONM results were continent after stoma closure. Of 2 patients with negative IONM results, 1 had fecal incontinence after closure of the defunctioning stoma and received a permanent sigmoidostomy. In the other patient the defunctioning stoma was deemed permanent due to decreased anal sphincter function. In 3 patients who underwent abdominoperineal excision, IONM assessed denervation of the IAS after performance of the abdominal part.

CONCLUSIONS

This study demonstrated that IONM of IAS innervation in rectal cancer patients is feasible and may predict neurogenic fecal incontinence.

Local transdermal delivery of phenylephrine to the anal sphincter muscle using microneedles

We propose pretreatment using microneedles to increase perianal skin permeability for locally targeted delivery of phenylephrine (PE), a drug that increases resting anal sphincter pressure to treat fecal incontinence. Microneedle patches were fabricated by micromolding poly-lactic-acid. Pre-treatment of human cadaver skin with microneedles increased PE delivery across the skin by up to 10-fold in vitro. In vivo delivery was assessed in rats receiving treatment with or without use of microneedles and with or without PE. Resting anal sphincter pressure was then measured over time using water-perfused anorectal manometry. For rats pretreated with microneedles, topical application of 30% PE gel rapidly increased the mean resting anal sphincter pressure from 7±2 cm H(2)O to a peak value of 43±17 cm H(2)O after 1 h, which was significantly greater than rats receiving PE gel without microneedle pretreatment. Additional safety studies showed that topically applied green fluorescent protein-expressing E. coli penetrated skin pierced with 23- and 26-gauge hypodermic needles, but E. coli was not detected in skin pretreated with microneedles, which suggests that microneedle-treated skin may not be especially susceptible to infection. In conclusion, this study demonstrates local transdermal delivery of PE to the anal sphincter muscle using microneedles, which may provide a novel treatment for fecal incontinence.

Neurophysiological testing in anorectal disorders

Neurophysiological tests of anorectal function can provide useful information regarding the integrity of neuronal innervation, as well as neuromuscular function. This information can give insights regarding the pathophysiological mechanisms that lead to several disorders of anorectal function, particularly fecal incontinence, pelvic floor disorders and dyssynergic defecation. Currently, several tests are available for the neurophysiological evaluation of anorectal function. These tests are mostly performed on patients referred to tertiary care centers, either following negative evaluations or when there is lack of response to conventional therapy. Judicious use of these tests can reveal significant and new understanding of the underlying mechanism(s) that could pave the way for better management of these disorders. In addition, these techniques are complementary to other modalities of investigation, such as pelvic floor imaging. The most commonly performed neurophysiological tests, along with their indications and clinical utility are discussed. Several novel techniques are evolving that may reveal new information on brain-gut interactions.

Transanal haemorrhoidal dearterialisation: nonexcisional surgery for the treatment of haemorrhoidal disease

BACKGROUND

Transanal haemorrhoidal dearterialisation (THD) is a nonexcisional surgical technique for the treatment of piles, consisting in the ligation of the distal branches of the superior rectal artery, resulting in a reduction of blood flow and decongestion of the haemorrhoidal plexus. The aim of this study was to assess the long-term efficacy of this treatment.

METHODS

The procedure was carried out using a proctoscope with a Doppler probe. The terminal branches were located with Doppler and then sutured.

RESULTS

From January 2000 to May 2006, we performed THD in 330 patients (180 men; mean age, 52.4 years), including 138 second-degree, 162 third-degree and 30 fourth-degree haemorrhoids. There were 23 postoperative complications (7 cases of bleeding, 5 thrombosed piles, 4 rectal haematomas, 2 anal fissures, 2 cases of dysuria, 1 of haematuria and 2 needle ruptures). The mean postoperative pain score was 1.32 on a visual analog scale. 219 patients were followed for a mean of 46 months (range, 22-79), including 100 patients with second-degree, 104 with third-degree and 15 with fourth-degree haemorrhoids. The operation completely resolved the symptoms in 132 patients (92.5%) with preoperative bleeding and in 110 patients (92%) with preoperative prolapse.

CONCLUSIONS

The efficacy and relapse rate of this procedure appears to be similar to that of traditional surgery and stapled haemorrhoidopexy. The technique was effective and safe for all degrees of haemorrhoids because of the excellent results, low complication rate and minor postoperative pain.

Rectoanal sensorimotor response in humans during rectal distension

PURPOSE

Rectal perception facilitates maintenance of continence and defecation. Whether perception is associated with motor changes in anorectum is unclear. We examined sensory and motor responses of the anorectum during rectal distention.

METHODS

Stepwise graded rectal balloon distensions were performed in 23 healthy subjects by placing a six-sensor probe in the anorectum. Manometric changes, rectoanal reflexes, and sensory thresholds were assessed. Studies were repeated in six subjects.

RESULTS

All subjects showed rectoanal inhibitory and contractile reflexes, but rectal perception was associated with an anal contractile response (sensorimotor response). In 4 subjects (17 percent) the sensorimotor response first occurred synchronously with a sensation of fullness (Group 1) and in 19 (83 percent) with a desire to defecate (Group 2). Mean balloon volume for inducing the sensorimotor response in Groups 1 and 2 were 80 +/- 14 ml and 96 +/- 26 ml (P > 0.05). The onset, amplitude, duration, and area under curve of the response were similar in both groups. At higher volumes of balloon distention, all subjects (n = 23) reported a desire and an urge to defecate. The sensorimotor response associated with an urge to defecate had higher amplitude (P = 0.01) and higher area under curve (P = 0.001) compared with that associated with a desire to defecate. Repeat studies showed good reproducibility (intraclass correlation coefficient = 0.9; P < 0.05).

CONCLUSIONS

A desire to defecate is associated with a unique, consistent, and reproducible anal contractile response: the sensorimotor response. This response could play an integral role in regulating anorectal sensation and function.

A Study of Fecal Incontinence in Patients with Chronic Anal Fissure: Prospective, Randomized, Controlled Trial of the Extent of Internal Anal Sphincter Division During Lateral Sphincterotomy

BACKGROUND

Troublesome fecal incontinence following a lateral internal sphincterotomy is often attributed to faulty surgical technique. However, it may be associated with coexisting occult sphincter defects. Whether continence is related to the extent of sphincterotomy remains debatable. The aim of the study is to identify fecal incontinence related to chronic anal fissure before and after lateral internal sphincterotomy and its relationship to the extent of internal anal sphincter division.

METHODS

One hundred eight patients with chronic anal fissure were prospectively studied before and after lateral internal sphincterotomy. A questionnaire was completed for each patient before and after surgery with regard to any degree of fecal incontinence. Fecal incontinence severity index was assessed using the Cleveland Clinic Incontinence Score. The patients with preoperative perfect continence were randomized into two groups (46 patients in each group): Group 1 underwent traditional lateral internal sphincterotomy (up to the dentate line) and Group 2 were underwent a conservative internal anal sphincterotomy (up to the height of the fissure apex or just below it).

RESULTS

Minor degrees of incontinence were present before surgery in 16 patients (14.8%). Results of the randomized trial revealed that temporary postoperative incontinence was newly developed in 6/92 of patients (6.52 %) who did not have it before surgery. Five of the six (10.86%) were in Group 1 one (2.17%) was in Group 2 (p = 0.039). Persistent incontinence occurred in two in Group 1 (4.35%). All of them were females. All have had a history of one or more vaginal deliveries.

CONCLUSION

A mild degree of fecal incontinence may be associated with chronic anal fissure at presentation rather than as a result of internal sphincterotomy. Troublesome fecal incontinence after lateral internal sphincterotomy is uncommon. Sphincterotomy up to the dentate line provided faster pain relief and faster anal fissure healing, but it was associated with a significant postoperative alteration in fecal incontinence than was sphincterotomy up to the fissure apex. Care should be exercised in female patients with a history of previous obstetric trauma, as internal anal sphincter division may further compromise sphincter function.

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.

Mechanisms controlling normal defecation and the potential effects of spinal cord injury

Spinal cord injury frequently leads to bowel dysfunction with the result that emptying the bowel can occupy a significant part of the day and reduce the quality of life. This chapter contains an overview of the function and morphology of the normal distal gut in the human, and of gut behaviour in normal defecation. In humans, this can be monitored and is described, but knowledge of the mechanisms controlling it is limited. Work on animals has shown that the intrinsic activity of the smooth muscles and their interactions with the enteric nervous system can program the activity that is necessary to expel waste material, but the external anal sphincter is controlled through somatic nerves. The gut however also receives input from the central nervous system through autonomic nerves, and a spinal reflex centre exists. Voluntary effort to induce defecation can influence all the control mechanisms, but the precise importance of each is not understood. The behaviour and properties of the individual muscles in the normal human rectum and anal canal are described, including their responses to intrinsic nerve stimulation and adrenergic and cholinergic agonists. The effects of established spinal cord injury are then considered. For convenience, supraconal and conal/cauda equina lesions are considered as two categories. Prolongation of transit times and disordered defecation are common problems. Supraconal lesions result in reduced resting anal pressures and increased risk of fecal incontinence. The acute effects of spinal cord injury are described, with injury causing ileus (prolonged total gastrointestinal transit times), constipation (prolonged colonic transit times) and fecal incontinence (passive leakage).

Faecal incontinence in patients with anal fissure: a consequence of internal sphincterotomy or a feature of the condition?

BACKGROUND AND OBJECTIVE

The function of the internal sphincter is disturbed in patients with chronic anal fissure due to persistent hypertonia and it may lead to a certain degree of incontinence. Our aim is to assess the results of lateral internal sphincterotomy and to identify any degree of incontinence related to the disease.

METHODS

This prospective study included a review of all patients operated upon by the authors who performed division of the internal sphincter at or below the upper limit of the fissure. A questionnaire was completed by each patient before surgery and then after surgery with regard to any degree of incontinence such as soiling of underclothes, control of flatus and accidental bowel motion.

RESULTS

126 patients with chronic anal fissure were studied. The male to female ratio was 0.8:1. Minor degrees of incontinence were present prior to surgery in 35 patients (28%) and in 31 (25%) patients after surgery, the majority of them were incontinent before surgery.

CONCLUSION

Based on the results of this study, minor degrees of incontinence could be a symptom of chronic anal fissure and not the sequelae of lateral internal sphincterotomy.

Rectal manometry in patients with isolated sacral agenesis

OBJECTIVE

The authors evaluated rectal manometry of children with sacral root abnormalities secondary to isolated sacral agenesis.

METHODS

The anorectal manometric recordings of seven patients with isolated sacral agenesis (four with partial agenesis and three with complete agenesis) were retrospectively evaluated and compared with tracings from healthy control subjects. Characteristics of the internal anal sphincter (IAS), the rectoanal inhibitory reflex (RAIR), voluntary external anal squeeze pressure, and threshold of rectal sensation to distension were analyzed. Characteristics of the patients' neurologic function with attention to urinary and fecal continence were obtained by chart review.

RESULTS

All seven patients had urinary and fecal incontinence. IAS resting pressure was the same in patients and control subjects. In the three patients with total sacral agenesis, IAS relaxation was more complete and lasted longer after balloon distention of the rectum. These patients also had significantly lower voluntary external anal squeeze pressure and blunted sensation of rectal distension.

CONCLUSIONS

Abnormal parasympathetic innervation associated with sacral agenesis is associated with changes in anorectal function. Manometric findings suggest that there is modulation of the RAIR by extrinsic innervation, which may explain the fecal incontinence in these patients.

Spatial localization and properties of pacemaker potentials in the canine rectoanal region

The present study investigated the spatial organization of electrical activity in the canine rectoanal region and its relationship to motility patterns. Contraction and resting membrane potential (E(m)) were measured from strips of circular muscle isolated 0.5-8 cm from the anal verge. Rapid frequency [25 cycles/min (cpm)] E(m) oscillations (MPOs, 12 mV amplitude) were present across the thickness of the internal anal sphincter (IAS; 0.5 cm) and E(m) was constant (-52 mV). Between the IAS and the proximal rectum an 18 mV gradient in E(m) developed across the muscle thickness with the submucosal edge at -70 mV and MPOs were replaced with slow waves (20 mV amplitude, 6 cpm). Slow waves were of greatest amplitude at the submucosal edge. Nifedipine (1 micro M) abolished MPOs but not slow waves. Contractile frequency changes were commensurate with the changes in pacemaker frequency. Our results suggest that changing motility patterns in the rectoanal region are associated with differences in the characteristics of pacemaker potentials as well as differences in the sites from which these potentials emanate.

Alpha-1 adrenoceptor blockade: potential new treatment for anal fissures

PURPOSE

Patients with chronic anal fissures are known to have high resting anal pressures that return to normal after successful surgical treatment. Internal anal sphincter activity is increased by sympathetic excitatory innervation via alpha adrenoceptors. The objective of this study was to determine the effect of alpha-1 adrenoceptor blockade on anal sphincter pressure in patients with and without chronic anal fissures.

METHODS

The effect on the anal canal pressure profile of a single oral 20 mg dose of indoramin, an alpha-1 adrenoceptor antagonist, on seven patients with chronic anal fissure and six healthy patients without a fissure was investigated.

RESULTS

Indoramin reduced anal resting pressures in those with anal fissure by a mean of 35.8 percent, from 106.9 +/- 22.15 cm H2O to 68.6 +/- 20.35 cm H2O, and in those without anal fissure by a mean of 39.9 percent, from 84.17 +/- 27.46 cm H2O to 52.17 +/- 24.78 cm H2O, after one hour. This pressure reduction persisted at three hours, and its magnitude is comparable to that obtained after internal sphincterotomy. The pressure reduction occurred over the whole length of the anal canal.

CONCLUSION

It is proposed that alpha-1 adrenoceptor antagonists could be a suitable treatment for chronic anal fissure and other painful conditions where reduction in anal pressure is warranted.

Anal pressure waves in patients with irritable bowel syndrome

PURPOSE

Many data suggest in irritable bowel syndrome a generalized smooth-muscle disorder, but data are scant concerning anal waves in patients with irritable bowel syndrome. The aim of the present study was first to propose a new method of anal pressure-wave analysis and second to apply this method to patients with irritable bowel syndrome.

METHODS

Spectral analysis was used in 20 healthy controls and 60 patients with irritable bowel syndrome to investigate anal pressure waves at rest during a standard anorectal test and during a maintained 12-ml anal distention.

RESULTS

Adaptation of the anal canal to maintained distention was similar in the two groups of subjects. Using a cluster analysis, three groups of anal waves were defined (in cycles per minute): ultra slow waves (0.9-3.3), slow waves (3.8-16.4), and simple waves (16.9-23). In the resting state only simple waves were found less prevalent in patients with irritable bowel syndrome. During maintained distention, ultra slow waves increase in both groups, but slow waves increase in patients with irritable bowel syndrome and simple waves decrease in controls.

CONCLUSIONS

Characterization of anal pressure waves is a simple procedure that is easy to perform in outpatients. Anal pressure waves of patients with irritable bowel syndrome have altered organization and respond differently to distention as compared with controls.

Topical phenylephrine increases anal sphincter resting pressure

BACKGROUND

Phenylephrine is an alpha1-adrenergic agonist which causes contraction of human internal anal sphincter muscle in vitro. Its intra-arterial administration in animals has been shown to increase resting sphincter pressure in vivo. In this study the effect of topical application of phenylephrine on resting anal pressure in healthy human volunteers was investigated.

METHODS

Twelve healthy volunteers had measurements of maximum resting sphincter pressure (MRP) and anodermal blood flow taken before and after topical application of increasing concentrations of phenylephrine gel to the anus. To determine the duration of effect of the agent, readings were taken throughout the day after a single application.

RESULTS

There was a dose-dependent rise in the resting anal sphincter pressure, with a small 8 per cent rise after 5 per cent phenylephrine (P = 0.012) and a larger 33 per cent rise with 10 per cent phenylephrine (mean(s.d.) MRP 85(12) cmH2O before versus 127(12) cmH2O after treatment, P < 0.0001). Thereafter no additional response was noted with higher concentrations of phenylephrine. The median duration of action of a single application of 10 per cent phenylephrine was 7 (range from 6 to more than 8) h.

CONCLUSION

Topical application of 10 per cent phenylephrine gel to the anus produces a significant rise in the resting anal sphincter pressure in healthy human volunteers. This represents a potential novel therapeutic approach to the treatment of passive faecal incontinence associated with a low resting anal sphincter pressure.

Internal anal sphincter: advances and insights

The internal anal sphincter, the smooth muscle component of the anal sphincter complex, has an ambiguous role in maintaining anal continence. Despite its significant contribution to resting anal canal pressures, even total division of the internal anal sphincter in surgery for anal fistulas may fail to compromise continence in otherwise healthy subjects. However, recently reported abnormalities of the innervation and reflex response of the internal anal sphincter in patients with fecal incontinence indicate its significance in maintaining continence. The advent of sphincter-saving surgery and restorative proctocolectomy has re-emphasized the major contribution of the internal anal sphincter to resting pressure and its significance in preventing fecal leakage. The variable effect of rectal excision on rectoanal inhibitory reflex has led to a reappraisal of the significance of this reflex in discrimination of rectal contents and its impact on anal continence. Electromyographic, manometric, and ultrasonographic evaluation of the internal anal sphincter has provided new insights into its pathophysiology. This article reviews advances in our understanding of internal anal sphincter physiology in health and disease.

Sacral reflexes: physiology and clinical application

Sacral reflexes consist of motor responses in the pelvic floor and sphincter muscles evoked by stimulation of sensory receptors in pelvic skin, anus, rectum, or pelvic viscera. These responses may be elicited by physical or electrical stimuli. They have been used in research studies of the pathophysiology of pelvic floor and anorectal disorders and many have been recommended for diagnostic use. These reflexes are described and discussed in this review. More rigorous evaluation of their value in the clinical assessment and care of patients with pelvic floor and sphincter disorders is required. Currently direct comparisons of the value of particular responses are generally not available, and few of these reflexes have proven validity for use in clinical diagnosis.

Spectrum of abnormal rectoanal reflex patterns in patients with fecal incontinence

PURPOSE

Abnormalities of rectoanal inhibitory or excitatory reflex in patients with fecal incontinence are well described. A spectrum of abnormal responses, other than those already described in the literature, has been observed in some patients with fecal incontinence and forms the subject of this report.

METHOD

Forty-three patients with idiopathic or traumatic fecal incontinence were studied to evaluate their reflex responses to balloon distention of the rectum, and results were compared with reflex responses of 29 control subjects with no anorectal complaints.

RESULTS

Control subjects revealed normal reflex responses consisting of initial excitation followed by inhibition in the proximal anal canal and an excitatory response in the distal anal canal. Patients who were incontinent revealed five different types of reflex patterns. Eleven patients (25.5 percent) with segmental sphincter defects from obstetric injuries exhibited no distal excitation but had normal response in the proximal anal canal (Group 1). Eleven patients (25.5 percent) with idiopathic incontinence exhibited normal proximal response but an inhibitory as opposed to excitatory response in the distal anal canal (Group 2). Three patients (7 percent) with iatrogenic trauma failed to register an excitatory response in the proximal or distal anal canal but revealed a normal inhibitory reflex (Group 3). Nine patients (21 percent) with idiopathic incontinence revealed excitatory response in the entire anal canal but no inhibition (Group 4). Nine patients (21 percent) with idiopathic incontinence had a normal reflex pattern (Group 5).

CONCLUSION

Excitatory and inhibitory components of rectoanal reflexes may selectively be abolished in neurogenic or traumatic insults to visceral and somatic anal sphincters, resulting in altered rectoanal reflex patterns.

Wide resection and reconstruction preserving fecal continence in recurrent anal cancer. Report of three cases

PURPOSE

A new operation was developed to treat patients with local recurrence of cancer at the anal margin after radiotherapy. This operation aims at resection of the tumor with oncologically safe margins, preservation of fecal continence, and reliable wound healing.

METHODS

After intensive radiotherapy, three patients with local recurrences of squamous-cell carcinoma of the anus refused to undergo abdominoperineal resection. These patients were treated by wide local excision and primary reconstruction. Wide local excision included perianal skin with subcutis and the anal canal including the internal sphincter up to the dentate line. To reconstruct the anus, the rectum was mobilized and brought down to the level of the perineum through the external sphincter and anastomosed to bilateral biceps femoris myocutaneous flaps.

RESULTS

In the first three patients no tumor recurrences have occurred, and fecal continence has been good.

CONCLUSION

The first results with this continence-preserving operation in patients with recurrent anal margin cancers after radiotherapy have been encouraging.