An analysis of anal sphincter pressure and anal compliance in normal subjects

Comparison of anorectal function measured using wearable digital manometry and a high resolution manometry system

There is a need for a lower cost manometry system for assessing anorectal function in primary and secondary care settings. We developed an index finger-based system (termed "digital manometry") and tested it in healthy volunteers, patients with chronic constipation, and fecal incontinence. Anorectal pressures were measured in 16 participants with the digital manometry system and a 23-channel high-resolution anorectal manometry system. The results were compared using a Bland-Altman analysis at rest as well as during maximum squeeze and simulated defecation maneuvers. Myoelectric activity of the puborectalis muscle was also quantified simultaneously using the digital manometry system. The limits of agreement between the two methods were -7.1 ± 25.7 mmHg for anal sphincter resting pressure, 0.4 ± 23.0 mmHg for the anal sphincter pressure change during simulated defecation, -37.6 ± 50.9 mmHg for rectal pressure changes during simulated defecation, and -20.6 ± 172.6 mmHg for anal sphincter pressure during the maximum squeeze maneuver. The change in the puborectalis myoelectric activity was proportional to the anal sphincter pressure increment during a maximum squeeze maneuver (slope = 0.6, R2 = 0.4). Digital manometry provided a similar evaluation of anorectal pressures and puborectalis myoelectric activity at an order of magnitude less cost than high-resolution manometry, and with a similar level of patient comfort. Digital Manometry provides a simple, inexpensive, point of service means of assessing anorectal function in patients with chronic constipation and fecal incontinence.

Transanal minimally invasive surgery for rectal polyps and selected malignant tumors: caution concerning intermediate-term functional results

PURPOSE

Transanal minimally invasive surgery (TAMIS) is gaining worldwide popularity as an alternative for the transanal endoscopic microsurgery (TEMS) method for the local excision of rectal polyps and selected neoplasms. Data on patient reported outcomes regarding short-term follow-up are scarce; data on functional outcomes for long-term follow-up is non-existent.

METHODS

We used the fecal incontinence severity index (FISI) to prospectively assess the fecal continence on the intermediate-term follow-up after TAMIS. The primary outcome measure is postoperative fecal continence. Secondary outcome measures are as follows: perioperative and intermediate-term morbidity.

RESULTS

Forty-two patients (m = 21:f = 21), median age 68.5 (range 34-94) years, were included in the analysis. In four patients (9.5%), postoperative complications occurred. The median follow-up was 36 months (range 24-48). Preoperative mean FISI score was 8.3 points. One year after TAMIS, mean FISI score was 5.4 points (p = 0.501). After 3 years of follow-up, mean FISI score was 10.1 points (p = 0.01). Fecal continence improved in 11 patients (26%). Continence decreased in 20 patients (47.6%) (mean FISI score 15.2 points, [range 3-31]).

CONCLUSIONS

This study found that the incidence of impaired fecal continence after TAMIS is substantial; however, the clinical significance of this deterioration seems minor. The present data is helpful in acquiring informed consent and emphasizes the need of proper patient information. Functional results seem to be comparable to results after TEMS. Furthermore, we confirmed TAMIS is safe and associated with low morbidity.

MR-FLIP: a new method that combines a functional lumen imaging probe with anatomical information for spatial compliance assessment of the anal sphincter muscles

AIM

Continence results from a complex interplay between anal canal (AC) muscles and sensorimotor feedback mechanisms. The passive ability of the AC to withstand opening pressure - its compliance - has recently been shown to correlate with continence. A functional lumen imaging probe (FLIP) is used to assess AC compliance, although it provides no anatomical information. Therefore, assessment of the compliance specific anatomical structures has not been possible, and the anatomical position of critical functional zones remains unknown. In addition, the FLIP technique assumes a circular orifice cross-section, which has not been shown for the AC. To address these shortcomings, a technique combining FLIP with a medical imaging modality is needed.

METHOD

We implemented a new research method (MR-FLIP) that combines FLIP with MR imaging. Twenty healthy volunteers underwent MR-FLIP and conventional FLIP assessment. MR-FLIP was validated by comparison with FLIP results. Anatomical markers were identified, and the cross-sectional shape of the orifice was investigated.

RESULTS

MR-FLIP provides compliance measurements identical to those obtained by conventional FLIP. Anatomical analysis revealed that the least compliant AC zone was located at the proximal end of the external anal sphincter (EAS). The cross-sectional shape of the AC was found to deviate only slightly from circularity in healthy volunteers.

CONCLUSION

The proposed method is equivalent to classical FLIP. It establishes for the first time direct mapping between local tissue compliance and anatomical structure, which is key to gaining novel insights into (in)continence. In addition, MR-FLIP provides a tool for better understanding conventional FLIP measurements in the AC by quantifying its limitations and assumptions.

Evaluation of anal sphincter resistance and distensibility in healthy controls using EndoFLIP ©

BACKGROUND

Ano-rectal disorders are common in the general population. Although they are not life threatening conditions, they do represent a social stigma and a reduced quality of life for the sufferer. The underlying physiology of muscle function contributing to ano-rectal competence is complex and there is room for a much better understanding so that treatments can improve.

METHODS

A cylindrically shaped, liquid filled bag (12 cm long), mounted on a catheter was inserted into the anus and positioned straddling the ano-rectal region in 20 healthy volunteers (10 females). Series of volume-controlled distensions (40 mL min(-1) to 40 mL) were carried out and data on 16 CSA at 5 mm apart and bag pressure were recorded. Provocative tests using squeeze and cough at bag volumes of 20, 30, and 40 mL were carried out.

KEY RESULTS

Ramp distension of the anal canal showed that the opening pressure for females (mean, 11 mmHg) was higher than for males (mean, 5 mmHg) (P < 0.001). Geometric profile of the anal canal at low distension volumes showed narrow bands at proximal and distal ends of the anal profile and shortening of a middle narrow zone at higher volumes. Inter-individual differences were observed in the behavior of the proximal end and the distal end of the anal profile during squeeze.

CONCLUSIONS & INFERENCES

This distensibility technique provides an important new way of studying the anal canal and hence may have a role in testing sphincter competence in patients with disorders.

Temperature-controlled radio frequency energy delivery (Secca procedure) for the treatment of fecal incontinence: results of a prospective study

PURPOSE

Fecal incontinence (FI) is a debilitating condition that can be socially and personally incapacitating. A broad range of treatment options, often stepwise, are available, depending on severity. This prospective study reports a large single-centered series of patients who have benefited of temperature-controlled radio frequency (Secca) energy delivered to the anal canal.

MATERIAL AND METHODS

This investigation was a single-center, nonrandomized, prospective, clinical study of a single patient group with each serving as the control. All patients had experienced FI for at least 3 months and had attempted, but were not satisfied, with the results of medical and/or surgical therapies. The study aims to evaluate changes in FI symptom scores and quality of life between the baseline and follow-up intervals.

RESULTS

Between March 2005 and March 2006, 15 Secca procedures were performed. All 15 patients were alive and in contact with the investigational site at time of 12 months. There were no long term complications. The mean Wexner score improved from 14.07 (+/-4.5) at baseline to 12.33 (+/-4.6) at 1 year (p=0.02). The mean fecal incontinence quality of life of life score was only improved in the depression subscore. There were no changes in endoanal ultrasound and anorectal manometry.

CONCLUSION

This prospective trial confirmed the safety of the Secca procedure. Although we demonstrated a significant improvement in the Wexner Score, these clinical results have to be mitigated because most patients remained in the moderate incontinences category as defined by the scoring system and did not improved their quality of life excepted in the depression subscore.

Closure mechanism of the anal canal in women: assessed by three-dimensional ultrasound imaging

PURPOSE

To describe the functional correlates of anal canal anatomy using 3 dimensional ultrasound imaging.

METHODS

Ten nulliparous women were studied by using a 10-cm bag of 20-mm diameter. The bag was placed along the anal canal and inflated with 20 to 45 ml water, in 5-ml increments. At each volume, a three-dimensional ultrasound volume of the anal canal was obtained while the subjects were at rest and squeeze. The ultrasound images were analyzed to determine the relationship between the bag cross-sectional area and bag pressure.

RESULTS

At low distension volumes, the bag is shaped like an "hourglass." The flared ends of the funnels correspond with the proximal and distal margins of the puborectalis muscle and external anal sphincter respectively. With increasing bag volumes, the length of completely closed segment of anal canal decreased. The last anal segment to open at rest was the one surrounded by all three structures. Anal contraction resulted in reduction of the anal canal cross-sectional area; the least compliant part of the anal canal was the one surrounded by external anal sphincter.

CONCLUSION

The internal anal sphincter, external anal sphincter, and puborectalis muscle are all involved in the anal canal closure function. During contraction, the external anal sphincter is the strongest component of anal canal closure mechanism.

Functional assessment of the anorectum in faecal incontinence

The functional ability of the anorectum to maintain continence is best assessed by a provocative assessment of continence to a standard load of rectally infused saline. Faecal incontinence is not caused by one condition. The combination of multiport anorectal manometry, electrophysiology and rectal sensory testing can identify several causes, which logically require different treatments. Only time and carefully conducted trials will establish whether such functional testing will be useful.

The use of a balloon catheter to improve evaluation in anorectal manometry

The squeeze pressure in the anal canal reflects the contribution of the external anal sphincter and is normally assessed manometrically by asking patients to contract their anal muscles. However, this is an artificial situation as normally the external sphincter contracts to retain rectal content. Some patients with normal anal sphincter anatomy and innervation record low squeeze pressures suggesting that the concept of voluntary squeeze is foreign. The aim of this study was to examine whether squeezing to retain a balloon mimics the physiology of defaecation more accurately. Patients undergoing routine anorectal manometry testing had in addition the inflation of a balloon catheter to the volume of the first and sustained sensation to simulate a faecal bolus within the rectum. The patient was asked to retain it when the balloon was subjected to gentle traction, thus contracting their anal sphincter to prevent passage of the balloon. Squeeze pressure was measured in response to voluntary contraction, the pressure generated to retain the balloon, then voluntary contraction again. Eighteen women and 2 men were tested. The median maximal squeeze pressures with the routine assessment was 131.0 cmH2O. This increased to 210.0 cmH2O when the patients attempted to retain the balloon and fell to 165.4 cmH2O when patients were reassessed with voluntary squeeze postintervention. 15 of the patients improved their squeeze pressures with traction on the balloon. External anal sphincter contraction is difficult for some patients to perform on request. With traction on a balloon catheter anal squeeze pressures improved in most patients. This indicates that many patients perform maximal anal squeeze pressures better once that muscle group has been tested in a more normal physiological function. This simple technique could improve the accuracy of anorectal manometry results and evaluation in a larger population of symptomatic patients is warranted.

Pathophysiology of adult fecal incontinence

Fecal incontinence occurs when the normal anatomy or physiology that maintains the structure and function of the anorectal unit is disrupted. Incontinence usually results from the interplay of multiple pathogenic mechanisms and is rarely attributable to a single factor. The internal anal sphincter (IAS) provides most of the resting anal pressure and is reinforced during voluntary squeeze by the external anal sphincter (EAS), the anal mucosal folds, and the anal endovascular cushions. Disruption or weakness of the EAS can cause urge-related or diarrhea-associated fecal incontinence. Damage to the endovascular cushions may produce a poor anal "seal" and an impaired anorectal sampling reflex. The ability of the rectum to perceive the presence of stool leads to the rectoanal contractile reflex response, an essential mechanism for maintaining continence. Pudendal neuropathy can diminish rectal sensation and lead to excessive accumulation of stool, causing fecal impaction, mega-rectum, and fecal overflow. The puborectalis muscle plays an integral role in maintaining the anorectal angle. Its nerve supply is independent of the sphincter, and its precise role in maintaining continence needs to be defined. Obstetric trauma, the most common cause of anal sphincter disruption, may involve the EAS, the IAS, and the pudendal nerves, singly or in combination. It remains unclear why most women who sustain obstetric injury in their 20s or 30s typically do not present with fecal incontinence until their 50s. There is a strong need for prospective, long-term studies of sphincter function in nulliparous and multiparous women.

Treatment of resistant anal fissure with advancement anoplasty

OBJECTIVE

The primary aim of this study was to assess the outcome of advancement anoplasty in the treatment of chronic anal fissure, resistant to conventional therapy. The secondary aim was to evaluate the anal resting pressure in these patients with resistant fissures.

PATIENTS AND METHODS

Over a five-year period eight patients (2 male, median age 55 years, range 20-74) with resistant anal fissure were referred from 6 centres. They had endured symptoms for a median of 8 years (range 2-20) and had undergone a median of 2 previous surgical procedures (range 1-3), including lateral sphincterotomy and anal dilatation. Anorectal physiological testing was performed on all patients who then underwent advancement anoplasty. The outcome was analysed retrospectively.

RESULTS

Pre-operative anorectal physiological testing showed a significantly lowered median maximal anal resting pressure of 42 mm H2O (range 12-72 mm H2O, normal range > 60 mm), P=0.03. All patients underwent advancement anoplasty. At a median of seven months follow-up (range 2-22) seven of eight patients had healed their fissure and were asymptomatic. The median healing time was four months (range 2-6).

CONCLUSION

Patients with chronic anal fissure, resistant to conventional therapy, may be successfully treated by advancement anoplasty. Healing time however, may be prolonged. In this series patients had a decreased anal resting pressure rather than anal hypertonia.

Medium-term results of permanent sacral nerve stimulation for faecal incontinence

BACKGROUND

Anal sphincter surgery for faecal incontinence is associated with significant morbidity and a variable outcome. Sacral nerve stimulation may provide a good functional outcome with minimal morbidity. This paper reports the experience in a single centre over 5 years.

METHODS

Fifteen consecutive patients (14 women), median age 60 (range 37-71) years, underwent temporary, and subsequent permanent, stimulation. All had incontinence to solid or liquid stool; the aetiology was obstetric injury (seven patients), scleroderma (four), idiopathic (two), fistula surgery (one) and repaired rectal prolapse (one). Median duration of symptoms was 6 (range 2-15) years. Clinical evaluation, endoanal ultrasonography, bowel diary, quality of life questionnaire (Short Form (SF) 36) and anorectal physiological testing were performed before and after stimulation.

RESULTS

Continence had improved in all patients at median follow-up of 24 (range 3-60) months. Eleven patients were fully continent. Episodes of faecal incontinence decreased from median (range) 11 (2-30) per week before stimulation to 0 (0-4) per week after permanent stimulation (P < 0.001). Urgency improved in all patients (median (range) ability to defer less than 1 (0-1) versus 8 (1-15) min; P = 0.01). 'Social function' and 'role-physical' subscales of the SF36 improved significantly. Mean resting pressure (35 versus 49 cmH2O with temporary stimulation; P < 0.05) and squeeze pressure increment (43 versus 69 cmH2O with permanent stimulation; P < 0.01) increased. Rectal sensitivity to initial distension changed (mean 47 versus 34 ml air; P < 0.05). There were no major complications.

CONCLUSION

Sacral nerve stimulation is a safe and effective treatment for faecal incontinence when conventional treatment has failed. There is minimal morbidity. The benefit is maintained in the medium term.

Gender differences in the longitudinal pressure profile of the anal canal related to anatomical structure as demonstrated on three-dimensional anal endosonography

BACKGROUND

Anal canal squeeze pressure is assumed to be due to external sphincter contraction, but the contribution of other muscles has not been explored.

METHODS

Ten male and ten nulliparous female asymptomatic subjects had three-dimensional anal endosonography and manometry. Incremental squeeze pressures at 0. 5-cm intervals, expressed as a percentage of the maximum pressure recorded anywhere in the canal, were related to the following anatomical levels: puborectalis, overlap between external anal sphincter (EAS) and puborectalis, external and internal anal sphincters, and external anal sphincter only. Levels were determined by coronal and sagittal endosonographic reconstructions.

RESULTS

Puborectalis was the same length in men and women (median 23.9 versus 27.1 mm) but represented a greater proportion of the anal canal in women (45 versus 61 per cent; P = 0.02). At the level of puborectalis alone, the pressure generated as a proportion of maximum anal canal pressure was 71 (range 32-100) per cent in men and 62 (range 32-100) per cent in women. At the level of the EAS alone, the pressure was 60 (4-98) per cent in men and 82 (41-100) per cent in women; where the external sphincter was overlapped by puborectalis, the pressure was 98 (60-100) per cent in men and 75 (47-100) per cent in women.

CONCLUSION

Maximal anal canal squeeze pressure is found where the puborectalis overlaps the EAS. This segment represents a significant proportion of anal canal length in women.

Manometric tests of anorectal function in healthy adults

OBJECTIVE

Although tests of anorectal function are useful in the assessment of defecation disorders, there is inadequate and inconsistent information regarding normative data. Also, there are discrepancies in manometric techniques and data interpretation. Our aim was to perform a comprehensive evaluation of anorectal function in healthy adults.

METHODS

We used a 6-mm diameter probe containing six radially arrayed microtransducers, and a 4-cm-long latex balloon for performing anorectal manometry in 45 healthy subjects who were controlled for gender and age. Sequentially, subjects were asked to squeeze, bear down, or blow up a party balloon. Subsequently, rectal sensation, rectal compliance, and rectoanal reflexes were assessed simultaneously by performing intermittent phasic balloon distentions. Additionally, balloon defecation, pudendal nerve latency, and saline continence tests were performed.

RESULTS

In men, the anal sphincter was longer (p < 0.05) and squeeze sphincter pressure and squeeze duration were higher (p < 0.01), but resting sphincter pressure was similar to that in women. When bearing down, although not significant, the defecation index was higher in men. Distinct thresholds for rectal sensation were identified but there was no gender difference. Likewise, rectal compliance and balloon expulsion time were similar. However, during saline infusion, the onset of first leak and total volume retained were higher (p < 0.001) and pudendal nerve latency was shorter (p < 0.05) in men. Overall, parity or age did not influence anorectal function.

CONCLUSIONS

This study represents the most comprehensive age- and gender-controlled assessment of anorectal function using solid state technology. Gender influences some parameters of anorectal function. Our results could serve as a valuable resource of normative data.

Anal endosonography in patients with anorectal symptoms after haemorrhoidectomy

BACKGROUND

Anorectal symptoms after haemorrhoidectomy are common and treatment is often empirical. Because of this, an audit was carried out of the value of anal endosonography in patients with anorectal symptoms after haemorrhoidectomy.

METHODS

Between May 1993 and February 1997, 16 patients (ten men and six women of median age 56 (range 35-77) years) were investigated by anal endosonography for anorectal symptoms after haemorrhoidectomy which involved anorectal incontinence (n = 10), anal pain (n = 4) and obstructive defaecation (n = 2). The findings were compared with those in a matched group of asymptomatic patients after haemorroidectomy.

RESULTS

Anal endosonography demonstrated an abnormality in 12 symptomatic patients. Of the ten patients with anorectal incontinence, endosonography showed an internal anal sphincter defect (n = 5), a combined sphincter defect (n = 2) and an isolated external anal sphincter defect (n = 1). Normal appearances were seen in all asymptomatic patients. The endosonographic abnormalities of the four patients with anal pain included internal anal sphincter defect (n = 1), extrinsic mass (n = 1), and intersphincteric abscess (n = 1). One of the two patients with obstructive defaecation had an isolated external anal sphincter defect on endosonography.

CONCLUSION

These results show a high yield of endosonographic abnormalities in patients who experience symptoms after haemorrhoidectomy. In particular, occult sphincter injury as a cause of incontinence in these patients can frequently be demonstrated.

The Favre system for anorectal manometry: comparison with other manometry systems in vitro and in healthy volunteers

BACKGROUND

The Favre system operates with airflow in a semi-closed circuit to transmit pressure. We aimed to evaluate the Favre system in comparison with other commonly used manometry systems.

METHODS

The Favre, Arndorfer, Arhan, and Synectics systems were evaluated in vitro and in 14 volunteers.

RESULTS

In vitro testing showed no relevant differences for latency, precision, or retest stability. In vivo, maximum resting pressure differed among all probes (P < 0.01) except for Arhan versus Arndorfer (NS). Maximum squeeze pressures differed among all probes (P < 0.01). Decrease of resting pressure during rectoanal inhibitory reflex was similar for Favre versus Arndorfer and Arhan versus Synectics (NS). Retest stability was higher with Favre than with Arndorfer (P < 0.05) and Synectics (P < 0.05) with regard to maximum resting pressure; it was higher with Favre than with Arhan (P < 0.01) and Arndorfer (P < 0.05) with regard to maximum squeeze pressure. Favre caused less discomfort than Synectics (P < 0.05) or Arndorfer (P < 0.05).

CONCLUSION

The Favre probe is an excellent and cost-efficient system for routine anorectal manometry.

Neurovascular intact muscle transposition for anal sphincter repair. Experimental model and experience with dynamic pacing

PURPOSE

To study muscle behavior for anal sphincter repair, radiologic, manometric, and histologic techniques in a dog animal model have been used. Special attention was given to the problem of resting length of the transposed muscle.

METHODS

The semitendinosus muscle of the dog could be transposed successfully to create a new anal sphincter based on an intact neurovascular pedicle. The parallel-fibered muscle was split at its distal end and encircled around the anal canal. Manometry was performed intraoperatively and postoperatively. A sufficiency high basal and squeeze pressure had to be obtained intraoperatively to guarantee a final continent neosphincter. This could be realized by a progressive stretching of the muscle until maximum squeeze is reached. In one animal a pacemaker was implanted, and postoperatively a fixed sphincter stimulation protocol was started. Muscle biopsies of the normal anal sphincter and the neosphincter were taken.

RESULTS

1) Muscle transposition gave a high degree of continence in this experimental model, with a mean resting pressure of +/- 40 mmHg and a mean squeezing pressure of +/- 73 mmHg. 2) Electric stimulation of the neosphincter in one animal influenced the resting pressure but not the squeeze pressure. 3) Muscle fiber type composition changed toward a slow fiber type composition after transposition of the fast muscle and even more after stimulation.

CONCLUSIONS

1) Creation of a muscle cuff around the anal sphincter can substitute normal anal sphincter. 2) Adequate stretch of muscle fibers is essential for continence. 3) Electrical pacing helps preserve resting tension and subsequent continence.

Abnormal internal anal sphincter fibrosis and elasticity in fecal incontinence

PURPOSE

We aimed to investigate the changes in the proportion of collagen and in the elasticity of the internal anal sphincter in patients with neurogenic fecal incontinence.

METHODS

Collagen content was studied in ten patients with neurogenic fecal incontinence (mean age, 51.5 years) and ten controls (age, 58.6 years) using histologic techniques to determine differences between incontinence and health and to determine the effect of aging. Changes in elasticity were also measured in 8 controls (mean age, 63 years) and 13 patients with neurogenic incontinence (mean age, 60 years) by recording the in vitro length-tension relationship of the freshly excised internal anal sphincter.

RESULTS

Incontinent patients had a significantly higher collagen content than controls (55 percent vs. 33 percent; P = 0.013). In incontinent patients the amount of collagen and the patients' ages correlated significantly (P = 0.001). There was a greater increase in stable tension per increase in muscle length in the strips from incontinent patients compared with controls.

CONCLUSIONS

Changes in fibrous tissue content are likely to influence muscle tone and responsiveness of the sphincter in fecal incontinence.

Discrepancies in anal manometric pressure measurement--important or inconsequential?

PURPOSE

Maximum resting and squeeze pressures have been the most widely employed parameters for manometric assessment of the anal sphincters. However, a single maximum value may not always be the best assessment.

METHODS

The aim of this study was to compare mean and maximum resting and mean and maximum squeeze pressures in a large sample population. All manometric pressure profiles were reviewed by a single individual blinded to the patient's age and diagnosis.

RESULTS

Four hundred sixty-six patients with a measurable high-pressure zone were included in this study. The study population was comprised of 279 females and 186 males. A significant difference was found between mean (56.26 mmHg) and maximum (79.2 mmHg) resting pressures (P < 0.01) and also between mean (81.25 mmHg) and maximum (119.50 mmHg) squeeze pressures (P < 0.01). A significant difference (P < 0.01) was also observed when compared by length of the high-pressure zone.

CONCLUSION

The measurement, documentation, and reporting of mean resting and mean squeeze pressures provide a better perspective of anal manometric results, since the two sets of values are significantly different (P < 0.01), regardless of the anal canal length. Therefore, these data support the standardized evaluation of both mean and maximum pressures in individual patients and in published series.

Anorectal function

A review in a historic perspective of the present knowledge of anorectal physiology is presented. The techniques used in the anorectal physiology laboratory are discussed. Application of new sophisticated techniques to anorectal physiology research in recent years continue to improve our knowledge of anorectal function. Anal continence and defecation depend on both the anal sphincter and the rectum. The assessment of patients with functional anorectal diseases should include a more complete physiologic evaluation of the anorectum than used previously.

Alteration of maximum anal resting pressure by digital rectal examination prior to manometry: analysis of agreement between repeat measurements

To study whether digital examination preceding anal manometry causes significant alteration of maximum resting pressure reading and to quantify the discrepancies, 78 individuals (64 incontinent, 14 controls) were investigated. Recordings of maximum resting pressure were taken before and after digital rectal examination. There was a mean discrepancy of only -1.8 cms H2O between the readings and excellent correlation, but analysis of agreement revealed a bias that tended to be greater with smaller measurements and unacceptable variability between test results. Furthermore, the bias was not related to age, gender, the grade of incontinence, maximum voluntary contraction, functional anal canal length and threshold volume. Digital rectal examination prior to manometry causes unpredictable results especially in patients with lower maximum resting pressures and should strictly be avoided.

Etiology and management of fecal incontinence

Fecal incontinence is a challenging condition of diverse etiology and devastating psychosocial impact. Multiple mechanisms may be involved in its pathophysiology, such as altered stool consistency and delivery of contents to the rectum, abnormal rectal capacity or compliance, decreased anorectal sensation, and pelvic floor or anal sphincter dysfunction. A detailed clinical history and physical examination are essential. Anorectal manometry, pudendal nerve latency studies, and electromyography are part of the standard primary evaluation. The evaluation of idiopathic fecal incontinence may require tests such as cinedefecography, spinal latencies, and anal mucosal electrosensitivity. These tests permit both objective assessment and focused therapy. Appropriate treatment options include biofeedback and sphincteroplasty. Biofeedback has resulted in 90 percent reduction in episodes of incontinence in over 60 percent of patients. Overlapping anterior sphincteroplasty has been associated with good to excellent results in 70 to 90 percent of patients. The common denominator between the medical and surgical treatment groups is the necessity of pretreatment physiologic assessment. It is the results of these tests that permit optimal therapeutic assignment. For example, pudendal nerve terminal motor latencies (PNTML) are the most important predictor factor of functional outcome. However, even the most experienced examiner's digit cannot assess PNTML. In the absence of pudendal neuropathy, sphincteroplasty is an excellent option. If neuropathy exists, however, then postanal or total pelvic floor repair remain viable surgical options for the treatment of idiopathic fecal incontinence. In the absence of an adequate sphincter muscle, encirclement procedures using synthetic materials or muscle transfer techniques might be considered. Implantation of a stimulating electrode into the gracilis neosphincter and artificial sphincter implantation are other valid alternatives. The final therapeutic option is fecal diversion. This article reviews the current status of the etiology and incidence of incontinence as well as the evaluation and treatment of this disabling condition.

The internal anal sphincter can not close the anal canal completely

We determined the maximum closing capability of the internal anal sphincter muscle ring in vitro and in vivo. The internal sphincter, 4 to 6 mm thick, cannot close the anal canal hermetically, not even during maximal contraction. The blood-filled anal cushions have to fill up an intrasphincteric gap of at least 7 to 8 mm in diameter.

Dynamic anal manometry: physiological variations and pathophysiological findings in fecal incontinence

A recently developed technique for dynamic anal manometry was used to study 40 healthy volunteers and 23 patients with fecal incontinence. Seven parameters of anal function were measured. Intraindividual variation of the parameters was studied in 5 females and 5 males. The results of dynamic anal manometry were compared with standard pull-through static anal manometry and correlated well. During opening of the anal sphincter at rest, compliance increased with increasing distension. Males had higher maximal closing pressures during squeeze and lower anal compliance during squeeze than females. There was no sex differences of the sphincter measurements at rest. Age had little effect, and gender had no effect on the measurements. With standard anal manometry, 6 of 23 patients with fecal incontinence both had maximal resting pressure and maximal squeeze pressure within the normal range. When dynamic anal manometry was used, all 23 patients showed one or more abnormal values. The method of dynamic anal manometry provides an opportunity for a more thorough assessment of anal sphincter function than previous manometric methods.

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

The human IAS has particular structural and functional characteristics. This smooth muscle constantly generates rhythmic electrical slow waves, but no action potentials. The slow waves are linked to calcium fluxes and both are essential for mechanical activity, i.e. the ASPW. The IAS is pharmacologically characterized by the presence of alpha excitatory and beta inhibitory adrenergic receptors. Cholinergic drugs have an indirect effect through the release of an inhibitory neurotransmitter, very probably VIP, from NANC nerves. The myogenic activity of the IAS is enhanced by its extrinsic sympathetic innervation. Thus, at rest, the IAS is in a state of partial tetanus and contributes approximately 55% of the MABP. Because the IAS ring cannot be completely closed, the anal mucosa and the haemorrhoidal plexuses fill the gap. By compressing these tissues, the IAS perfectly closes the anal canal to retain not only solids but also fluid stool and gas. Acute rectal distension and rectal activity, mainly through intramural pathways, induce reflex IAS relaxation, permitting the rectal contents to be sampled by receptors in the upper anal canal while continence is temporarily maintained by EAS activity and by expansion of the haemorrhoidal cushions. There is a correlation between the volume of rectal distension and the parameters of IAS relaxation. At maximal IAS relaxation, ASPW are absent, indicating the completeness of the inhibition. Although this RAIR is not essential for defecation, insufficient relaxation may be implicated in constipation. Hyperactivity of the IAS resulting in a high MABP and AUSPW has been considered both as a cause and as an effect in haemorrhoids and anal fissure. Continence for fluids and gas is impaired if IAS activity is decreased (i.e. a low MABP), either by direct trauma or by damage of its sympathetic innervation. Severe faecal incontinence will develop when the contractility of both the IAS and the EAS is affected.

Reflex anal dilatation: effect of parting the buttocks on anal function in normal subjects and patients with anorectal and spinal disease

Anal dilatation in response to gentle parting of the buttocks has been advocated as a sign of sexual abuse in children, but nothing is known of the physiology of this response or its existence in normal subjects, in patients with spinal disease, and in patients with a weak sphincter and whether it can be elicited after training. To answer these questions we investigated the effect of parting the buttocks on anal function. Combined anal manometry and electromyography was conducted in six normal subjects (five men, one woman, aged 19-53 years), in 18 patients with faecal incontinence (three men, 15 women, aged 30-80 years), and in seven paraplegic patients (six men, one woman, aged 25-36 years), in four of whom the posterior sacral roots had been cut. Parting the buttocks in normal subjects reduced the pressure in the anal canal from 102 (20) to 14 (3) cm H2O (mean (SEM), p less than 0.00001), but did not cause the anus to gape. This drop in pressure was associated with increased electrical activity in the external anal sphincter. Normal subjects could consciously relax the external anal sphincter and reduce the anal pressure but not so as to result in anal gaping during traction on the buttocks, even after anal dilatation. Stimulation of the anal lining by moving a probe in and out of the anal canal increased the activity of the external anal sphincter, raising anal pressures. Paraplegic patients who had lost conscious control of their external sphincters showed anal gaping when the buttocks were parted. A similar phenomenon was seen in patients with faecal incontinence who had weakness of the external anal sphincter, while incontinent patients with weakness of both sphincters showed anal gaping even at rest. Inasmuch as the results of our study can be applied to children, the data suggest that reflex anal dilatation should only be used to support a diagnosis of sexual abuse if sphincter function is otherwise normal and there is no evidence of cerebrospinal disease. Although our results do not support the notion that children could become so conditioned to repeated digital or penile penetration of the anus that they can cause the anus to gape when the buttocks are parted, neither do they exclude it.

A technique for the dynamic assessment of anal sphincter function

A technique which renders continuous measurement of the cross-sectional area and pressure of the anal canal possible during distension and contraction of the anal sphincter has been developed. Electromyography of the external sphincter is measured simultaneously. With this technique a more detailed assessment of anal sphincter function is possible, including the opening and closing pressures of the sphincter at rest, anal compliance, anal hysteresis and the maximal closing pressure during squeeze. The results of in vitro measurements, measurements on 16 healthy subjects and 6 patients with faecal incontinence are presented.

Transducer manometry and the effect of body position on anal canal pressures

Anal canal manometry is performed conventionally with balloons, sleeves, perfused or nonperfused open-tipped catheters, or with multiport probes. The authors constructed a new manometer with four transducers embedded in a probe (15 mm outside diameter) and oriented radially, 90 degrees apart. The transducer probe was validated in 27 healthy volunteers by comparing its performance to that of a standard four-port perfused manometer and then used to measure anal canal and rectal pressures in body positions more physiologic (standing, sitting) than that usually employed (left lateral) for such measurements. Both devices measured similar anal canal resting pressure in the left lateral position (mid canal, 58 +/- 3 mm Hg perfused vs. 62 +/- 4 mm Hg transducer; P greater than 0.05). The transducer probe, however, recorded higher squeeze pressures (mid canal, 100 +/- 6 mm Hg perfused vs. 143 +/- 14 mm Hg transducer; P less than 0.05). The transducer probe detected higher intrarectal and resting anal canal pressures when subjects were standing or sitting, compared with the left lateral position (rectum, 3 +/- 1 mm Hg left lateral; 17 +/- 2 mm Hg standing; 20 +/- 1 mm Hg sitting; P less than 0.05; mid anal canal, 57 +/- 3 mm Hg left lateral; 86 +/- 4 mm Hg standing; 81 +/- 5 mm Hg sitting, P less than 0.05). The rise in resting anal canal pressure was uniform circumferentially. Neither anal canal length nor squeeze pressure changed with change in position. The authors concluded that 1) transducer manometry recorded similar resting but higher squeeze pressures compared with perfused manometry; 2) transducer manometry recorded the same radial variation in anal canal resting and squeeze pressures as that recorded by the perfused manometer; and 3) standing and sitting caused a four-fold rise in intrarectal pressure, which was associated with a concomitant rise in resting anal canal pressure.

Anal manometry with microtransducer technique before and after restorative proctocolectomy. Sphincter function and clinical correlations

Anal manometry, with microtransducer technique, was performed in 55 patients after restorative proctocolectomy. Forty-two patients were followed regularly from before surgery until 12 months after surgery, and 23 patients until 24 months of function. Postoperatively, sphincter function was severely impaired. At 12 months, the mean height was less than 60 percent, mean area less than 50 percent, and mean length less than 90 percent of the preoperative values of the high pressure zone. There was no improvement between 12 and 24 months. Mean maximal squeeze pressure was restored at 12 months. Rectoanal inhibitory reflex was constantly present preoperatively, but in only 4 of 30 patients, postoperatively. Those patients with preoperative resting pressure 100 cm H2O or greater had significantly higher resting tones at 12 months than those with less than 100 cm H2O. Patients with 5 or fewer bowel movements every 24 hours had significantly higher resting tones than those with more than 6 movements every 24 hours (66 vs. 45 cm H2O). Patients with deferral 60 minutes or greater had significantly higher resting pressures than those with deferral less than 30 minutes (65 vs. 44 cm H2O). No correlation was found between resting pressure and state of continence.

The composition of anal basal pressure. An in vivo and in vitro study in man

The maximal anal basal pressure (MABP) was measured with probes of 0.3, 1, 2 and 3 cm diameter in 21 subjects, 60 years old, without anal pathology. The components of MABP were analyzed by inducing a maximal internal sphincter (IS) relaxation, taking pressure measurements in the conscious state and during narcosis with curarization. In seven cases pressure measurements were done on isolated anorectum after abdominoperineal rectum amputation. MABP increases with probe diameter before as well as during anaesthesia with curarization. The contribution of the striated sphincter tonic activity is constant within the range of probe diameters used. At rest, i.e. when the 0.3 cm diameter pressure recording probe is used, 30% of MABP is made up by striated sphincter tonic activity, 45% of it is due to nerve induced IS activity, 10% to purely myogenic IS activity and 15% can be attributed to the expansion of the haemorrhoidal plexuses. Although MABP is mainly based on active forces generated by the smooth and striated sphincter apparatus, the presence of the anal cushions is essential for perfect anal continence, as they have to fill the gap within the IS ring to hermetically close the anal canal. The global IS activity, contributing 50-60% of MABP at rest, can completely be inhibited by a maximal rectoanal inhibitory reflex. Stretching of passive elements starts at 1 cm anal distension, but steeply increases thereafter, accounting for 65% of the MABP at 3 cm anal distension. It is deduced that optimal stool diameter is about 2 cm.

Role of constipation and anal hypertonia in the pathogenesis of haemorrhoids

The hypothesis that haemorrhoids result from chronic constipation was investigated by studying bowel habit, anal pressure profiles and anal compliance in 13 men and 10 women with prolapsing haemorrhoids, 12 women with severe constipation and 14 male and 11 female control subjects. Defaecation was less frequent in women than in men (P less than 0.01) but was independent of the presence of haemorrhoids. Patients with haemorrhoids and control subjects reported similar stool consistency and rarely admitted to straining. Severely constipated women complained of infrequent defaecation, straining at stool and hard motions, but none had prolapsing haemorrhoids. Haemorrhoids were associated with significantly longer anal high-pressure zones and significantly greater maximum resting pressures at all levels of anal distension (P less than 0.01), but minimum residual pressure during rectal distension and maximum squeeze pressure were not significantly different from control subjects. Maximum resting pressure was increased in patients of both sexes with haemorrhoids, but this reached statistical significance only in men (P less than 0.001). Constipated women had normal anal pressure profiles and maximum anal pressures. These data show that patients with haemorrhoids are not necessarily constipated but tend to have abnormal anal pressure profiles and anal compliance. Chronically constipated women do not necessarily have haemorrhoids but have normal anal pressure profiles and compliance. This casts doubt upon the hypothesis that haemorrhoids are caused by constipation.

The mechanics of the anal sphincter complex

The anal sphincter complex consists of circumferentially arranged muscle fibres, which surround a relatively thick anal lining. This apparatus was modelled mechanistically as two concentric homogeneous isotropic linear elastic cylinders. The inner cylinder (anal lining) was considered to be thick walled, while the outer (the circular muscle) was assumed to be thin walled. The model predicts that the anal sphincter tension varies linearly with luminal diameter. This prediction was confirmed experimentally under normal conditions as well as during external sphincter contraction and internal sphincter relaxation. Under conditions of negligible hoop stress in the anal lining the model also predicts that the intra-luminal pressure falls to zero before the luminal diameter reaches zero. Hence, an autoregulatory mechanism of anal cushion thickening, as the luminal pressure falls to zero, to produce anal closure was proposed. Deficiencies in this autoregulation mechanism may explain anal incontinence and the obstructed defaecation often found in subjects with haemorrhoids.