Review article: the management of pelvic floor disorders

Transcription

1 Aliment Pharmacol Ther 2004; 19: doi: /j x Review article: the management of pelvic floor disorders O. CHEUNG & A. WALD University of Pittsburgh Medical Center, Pittsburgh, PA, USA Accepted for publication 23 December 2003 SUMMARY Anorectal disorders, such as faecal incontinence, defecation difficulty and conditions associated with anorectal pain, are commonly encountered in the practices of gastroenterologists, urogynaecologists and colorectal surgeons. The evaluation of these disorders has been very much improved by the development and wider availability of diagnostic tests, such as manometry, endo-anal ultrasound, static and dynamic pelvic magnetic resonance imaging and electromyography. After briefly reviewing the normal anatomy and physiology of the anorectum, the pathophysiology and diagnostic approaches to faecal incontinence, defecation disorders and functional anorectal pain are discussed. Until recently, the management of these disorders has been largely anecdotal. However, our therapeutic armamentarium has been expanded by pharmacological agents, such as nitrates, calcium channel blockers and botulinum toxin, as well as the development of novel techniques, such as sacral nerve stimulation. These and other pharmacological, behavioural and surgical approaches are reviewed with respect to the robustness of evidence to support their efficacy in patients with these disorders. INTRODUCTION Disorders of the pelvic floor are of interest to many physicians who specialize in organ systems within this region. Gastroenterologists and colorectal surgeons are especially interested in disorders of the posterior compartment, which broadly may be divided into faecal incontinence, disorders of defecation and conditions associated with chronic or recurrent pain. Diagnostic studies which provide some understanding of the pathophysiology of the underlying complaint are available or are in development, but the precise mechanisms which underlie many of these complaints are often incompletely understood. Unfortunately, many treatments which are advocated for these disorders are endorsed less by evidence-based medicine and more by eminence-based recommendations. This review Correspondence to: Dr A. Wald, Professor of Medicine, University of Pittsburgh Medical Center, PUH, Mezzanine Level, C-Wing, 200 Lothrop Street, Pittsburgh, PA 15213, USA. summarizes the therapies which are available and suggests directions for future research concerning the management of anorectal disorders. ANATOMY AND PHYSIOLOGY OF THE ANORECTUM The rectum serves as a storage organ and as a conduit from the colon to the anal canal. The anal canal is defined proximally by the levator ani muscles, which form part of the pelvic floor, and includes the puborectalis muscle which creates the anorectal angle. 1 Two sphincters encircle the anal canal the internal anal sphincter, which is a continuation of the circular smooth muscle of the rectum, and the external anal sphincter, which consists of striated muscles innervated by the pudendal nerves arising from S2, S3 and S4. Extrinsic innervation of the internal anal sphincter is by sympathetic and parasympathetic autonomic nerves. Both continence and defecation rely heavily on the appropriate functioning of the puborectalis muscle, Ó 2004 Blackwell Publishing Ltd 481

2 482 O. CHEUNG & A. WALD internal anal sphincter and external anal sphincter, but other factors play important roles. These include stool consistency, volume and delivery of colon contents to the anorectum, rectal storage capacity, anal and rectal sensations and cognitive and behavioural influences. The evaluation of patients with complaints of incontinence and defecation difficulties should include a detailed history and physical examination, which is supplemented by appropriate diagnostic studies in selected patients. 2 PATHOPHYSIOLOGY OF FAECAL INCONTINENCE Although abnormalities of anorectal continence mechanisms often contribute to faecal incontinence, impairment of one mechanism need not result in incontinence if there are no additional derangements and compensating mechanisms are in place. One example is the frequent presence of external anal sphincter weakness in patients with multiple sclerosis, who nevertheless remain continent when constipated but who develop incontinence in the presence of diarrhoea. Indeed, alterations of stool consistency and delivery to the rectum are important therapeutic principles in many patients with faecal incontinence. The pathophysiology of faecal incontinence may be classified as shown in Table 1. Table 1. Pathophysiology of faecal incontinence 1 Impaired rectal/colonic storage function A Inflammation: inflammatory bowel disease B Surgery: proctectomy C Fibrosis: radiation 2 Anal sphincter weakness A Internal anal sphincter Trauma (sphincterotomy) Neurological (diabetes) Degenerative (scleroderma) B External anal sphincter Trauma (vaginal delivery) Neurological (pudendal neuropathy, spinal cord) Degenerative (Atrophy) C Puborectalis Neurological (peripheral, central nervous system) Trauma (high tear) 3 Rectal sensory impairment A Neurological: i.e. central nervous system B Muscle hypotonia: i.e. megarectum 4 Overflow A Faecal impaction DIAGNOSTIC TESTING FOR FAECAL INCONTINENCE Various diagnostic tests which may provide insights into the pathophysiology of faecal incontinence are available to assess anorectal structures and functions. In general, these tests are most useful when the aetiology of incontinence is uncertain after the initial clinical evaluation, or when making therapeutic decisions for which such information may affect outcome (i.e. damage to the pudendal nerves in the presence of anal sphincter damage may adversely alter prognosis after a surgical repair and may dictate a conservative approach). The evidence to support this approach is sometimes contentious and the choice of testing is often influenced by physicians beliefs and the availability of diagnostic studies. 3 Endoscopy may be employed to detect inflammation of the colon and rectum and to identify possible causes of a recent change in bowel habits. In addition to this modality, the tests of greatest clinical utility are anorectal manometry, endo-anal ultrasonography and needle electromyography of the external anal sphincter and puborectalis muscle. 2 5 A new and potentially important technique is static and dynamic pelvic magnetic resonance imaging. Pelvic magnetic resonance imaging provides superior characterization of the external anal sphincter and the puborectalis muscle compared with endo-anal sonography, and the detection of external anal sphincter atrophy is a good predictor of poor results after repair of external anal sphincter defects. 5, 6 Dynamic pelvic magnetic resonance imaging provides excellent imaging of pelvic floor structures during squeeze and expulsion manoeuvres to characterize perineal descent, dyssynergia and pelvic organ prolapse. 6 The precise role of this new imaging modality in clinical practice remains to be determined. Other tests which are less helpful or of uncertain utility include barium proctography and pudendal nerve terminal motor latency measurements. The validation and utility of diagnostic tests have been reviewed elsewhere. 2, 4 Barium proctography has been criticized on several grounds, including poor inter-observer agreement in critical readings, the wide range of normal values of rectal emptying, the poor correlation of results with symptoms, colonic transit and manometry, and the failure of the test to reflect normal defecation in a private setting. 4 Pudendal nerve terminal motor latency measurements lack sensitivity and specificity for the

3 REVIEW: MANAGEMENT OF PELVIC FLOOR DISORDERS 483 detection of external anal sphincter muscle weakness caused by pudendal nerve damage, the test reproducibility is poor and, in contrast with earlier studies, the test may not predict improvement or failure after surgical repair of anal sphincter defects. TREATMENT OF FAECAL INCONTINENCE The management of faecal incontinence encompasses the modification of stool consistency and delivery using dietary and pharmacological modalities, behavioural interventions and surgery to correct underlying abnormalities. An innovative technique involving the stimulation of sacral nerve roots appears to be promising and may soon become clinically available for selected patients. Medical and pharmacological treatments In patients who exhibit overflow incontinence associated with faecal impaction, disimpaction and colon cleansing provide immediate cessation of soiling. However, such patients often remain at increased risk for recurrence of incontinence and require an ongoing bowel management programme which involves habit training and laxatives. 7 This involves regularly scheduled attempts to defecate with the assistance of osmotic laxatives, such as magnesium salts, polyethylene glycolcontaining solutions and non-absorbable sugars such as lactulose and sorbitol. Stimulant laxatives are employed as rescue therapy if there is no defecation for 3 days. Short-term success rates of 60 80% have been reported, 8 but high long-term recurrence rates require ongoing vigilance. 7 When incontinence is associated with decreased colonic and rectal storage capacity or with chronic diarrhoea, treatment is directed towards reversing the underlying inflammation or, if not an option, modifying the stool volume, consistency and delivery. It is often beneficial to reduce dietary fibre intake in combination with anti-diarrhoeal drugs which slow colonic transit. Of the anti-diarrhoeal agents available, loperamide is preferred as it has no central nervous system effects and may increase internal anal sphincter tone. 9 If the response to peripherally acting anti-diarrhoeal agents is sub-optimal, opioids which have central nervous system effects may be more effective in treating chronic diarrhoea. In patients with diarrhoea associated with irritable bowel syndrome, medications with anticholinergic effects, such as tricyclic agents and smooth muscle relaxants, may be effective. Alosetron is a 5-hydroxytryptamine-3 antagonist which has been approved for women with irritable bowel syndrome and diarrhoea predominance. Because a number of cases of severe constipation and ischaemic colitis have occurred in patients taking alosetron, the drug is now available only in a limited capacity with close observation by prescribing physicians. Patients with isolated internal anal sphincter abnormalities are characterized by decreased anal canal tone. Characteristically, they have faecal soiling in the presence of normal bowel habits. If tolerated, the use of a polyurethane or a cotton anal plug restores passive barrier function and serves as an absorbent as well. 10, 11 Such plugs can be worn on a regular basis or for limited periods of time and are highly successful for those patients who can tolerate them. The use of a cotton plug is an inexpensive approach which works well in many patients (A. Wald, personal observations). Treatment with topical phenylephrine gel for isolated internal anal sphincter dysfunction has also been tested. Although this a 1 agonist increased resting anal canal tone by approximately 30% in healthy volunteers, clinical trials in patients with seepage associated with internal anal sphincter dysfunction have been disappointing. 12 Currently, there are ongoing studies of phenylephrine gel in patients with ileo-anal pouches without pouchitis. 13 Similar studies with other a agonists have recently been reported in abstract form. 14 Biofeedback Both pelvic floor training and biofeedback, the latter based on the principles of operant conditioning first enunciated by Engel et al., 15 have been reported to be effective in many patients with faecal incontinence associated with impaired functioning of the puborectalis muscle and the external anal sphincter. In contrast with pelvic floor re-training, which is directed exclusively at re-educating weakened or impaired muscles, biofeedback often includes techniques to alter rectal sensation and sphincter muscle responsiveness to intra-rectal stimuli such as balloon distension. However, the biofeedback literature does not reflect a unified mechanistic approach. 7, 16 Some investigators have emphasized the enhancement of the responsiveness of the external anal sphincter to rectal distensions, 17 whilst others have focused on increasing the force and

4 484 O. CHEUNG & A. WALD 18, 19 duration of external anal sphincter contractions; yet others have attempted to modify both. 20, 21 There appears to be a general consensus that the improvement of thresholds of perception of rectal sensation and the synchronization of external anal sphincter contractions to rectal stimulation are important factors associated with improvement. 2, 7 In contrast, increased striated muscle strength and endurance after biofeedback training have not been shown consistently. 7 There is widespread agreement that biofeedback is effective in approximately 75% of patients who fulfil the entry criteria, and has no adverse consequences. 22 Unfortunately, after almost 30 years following Engel s seminal report, the biofeedback literature has been plagued by methodological inadequacies, few long-term follow-up studies and the absence of consistent and validated outcomes. 2, A recent Cochrane review concluded that there was insufficient evidence from trials of biofeedback and exercises for faecal incontinence to determine whether such treatments are effective. 21 Moreover, there is no consensus concerning which components of biofeedback are important, including the critical role of the patient therapist relationship. To address these issues, a recent study examined critical components of the biofeedback process by randomizing 171 patients with faecal incontinence into four therapeutic groups. 26 In all groups, slightly more than 50% of patients reported clinical improvement on an intention-to-treat analysis. However, there were no differences between those patients who received advice about strategies to reduce incontinence from nurse therapists, those who received both advice and verbal instructions about sphincter exercises, those who received advice together with a hospital-based biofeedback programme and those who received both hospital and home electromyographic biofeedback. Moreover, improvement was maintained for at least 1 year and anal sphincter pressure changes were similar in all groups. 26 Determining those elements of biofeedback which are important to therapeutic efficacy is an area of needed study, as biofeedback is both time consuming and provider intensive. At present, the evidence for using instrument-based training is insufficient. or implantation of artificial material and, as a last resort, diversion of the faecal stream. A new technique based on the stimulation of the sacral nerves is under investigation. Anal sphincteroplasty has been performed for many years and is based on the straightforward premise of repairing an anatomically disrupted anal sphincter complex. The use of anal sonography to demonstrate disruptions of the anal sphincter has largely replaced the more invasive and painful electromyographic mapping of the external sphincter. 4, 5 Although many studies have reported short-term improvement of faecal continence in up to 85% of patients, long-term followups have been disappointing with failure rates of approximately 50% after months. In three recent representative series, full continence after sphincteroplasty was maintained in only 28% of patients after a mean follow-up of 40 months, 27 and in only 11 14% of patients followed for over 69 months. 28, 29 Suggested predictive factors for treatment failure include the presence of an internal anal sphincter defect, prolongation of pudendal nerve terminal motor latencies, atrophy of the external anal sphincter, as demonstrated by pelvic magnetic resonance imaging, 6 and the presence of irritable bowel syndrome with diarrhoea predominance. In the absence of demonstrable anal sphincter defects, the efficacy of surgical approaches designed to correct abnormalities of the pelvic floor, such as anterior levatorplasty, post-anal repair and total pelvic floor repair, is unproven. In one study, eight of 12 patients after anterior levatorplasty and seven of 12 patients after post-anal repair failed to achieve continence, 27 compared with four of 12 after total pelvic floor repair. 30 Similarly, six of 11 patients after total pelvic floor repair and six of nine patients after post-anal repair showed no change of incontinence. 31 A Cochrane review concluded that there was insufficient evidence to determine whether clinically important differences between various alternative procedures existed to guide clinical practice. 32 These procedures cannot be recommended for patients with neurogenic incontinence or in the absence of structural defects. Surgery Surgical procedures for faecal incontinence may be classified as those that repair a damaged sphincter, those that create a neosphincter using nearby muscles Other surgical approaches Replacement of a damaged or non-functioning anal sphincter complex has been reported using nearby muscles (dynamic graciloplasty) or an artificial implanted

5 REVIEW: MANAGEMENT OF PELVIC FLOOR DISORDERS 485 sphincter. 33 Recent reviews of both procedures have suggested that improved continence occurs in over 50% of patients on intention-to-treat analyses, but this is tempered by significant morbidity, including infections, device malfunctions and, in the case of the artificial sphincter, a high percentage of explantation of the device. Such procedures are best performed for the therapeutically desperate by surgical teams with considerable experience. For those with severe refractory incontinence, a diverting colostomy may provide dramatic improvement, although no formal assessment of the quality of life has been published. 7 Sacral nerve stimulation Sacral spinal nerve stimulation is a new therapeutic approach for patients with faecal incontinence which is associated with structurally intact anal sphincters. This technique arose as an extension of the successful use of this modality for urinary voiding and continence disorders, together with the realization that stimulating electrodes implanted into pelvic floor muscles are prone to infection, migration and fibrous tissue reactions. 37 The procedure involves three phases: (i) location of the sacral spinal nerves by percutaneous probing with a needle electrode to identify the nerve root which maximally stimulates anal sphincter contraction; (ii) temporary placement of an electrode to chronically stimulate the nerve root identified as the most efficient during acute testing; (iii) permanent implantation of a neurostimulator for chronic therapeutic stimulation. In patients who successfully complete the first two phases, clinical improvement of faecal incontinence has been confirmed in both short , 40 and long-term studies, especially in patients who have faecal incontinence at the first urge to defecate ( urge incontinence ). Clinical parameters include a substantial decrease in episodes of liquid and solid stool incontinence and significant improvement of quality of life parameters, as assessed by validated quality of life questionnaires, for periods ranging from 6 months to over 5 years. Objective physiological changes have included increases in both resting and squeeze pressures, increased squeeze durations, decreased thresholds of rectal sensation and increased time of retention of a saline load. It has been hypothesized that there may be possible transformation of type II fast twitch muscles to slow twitch type I fibres which are more resistant to fatigue, although there is little evidence to support this. A multi-centre study in the USA is currently in progress. PATHOPHYSIOLOGY OF DEFECATION DISORDERS Defecation difficulty may arise as a result of disordered movement through the colon and/or anorectum. Two major paradigms are currently used to explain constipation, which are not mutually exclusive in a given patient. The first of these is slow transit constipation, in which there is failure of co-ordinated motor activity to move luminal contents through the colon. In some patients, slow transit constipation may be associated with dietary factors, such as caloric deficiency, with medications which alter motility or with systemic diseases, such as neurological, metabolic and endocrine disorders. Other patients with slow transit constipation exhibit abnormalities of the enteric nerves, such as decreased volume of interstitial cells of Cajal and other neural elements. 41 The alternative mechanism involves disorders of the anorectum and pelvic floor, causing outlet dysfunction as listed in Table 2. In this paradigm, the primary failure is an inability to adequately evacuate contents from the rectum. A classical example of outlet dysfunction is Hirschsprung s disease, a congenital disorder characterized by obstipation from birth and associated with colonic dilatation proximal to the non-relaxing, non-propulsive segment of the distal bowel. Intra-mural ganglion cells of the submucosal and myenteric plexuses are absent in the affected segment of distal bowel as a result of failure of migration of ganglion cell precursors from the neural crest into the hindgut during foetal development. Table 2. Pathophysiology of outlet dysfunction constipation Mechanism Propulsive forces Weak Misdirected Resistance Striated muscle Failure of co-ordinated relaxation during attempted expulsion Smooth muscle Aganglionosis Disease Megarectum, neuromuscular disorders, pain that inhibits bearing down Rectocoele Pelvic floor dyssynergia (anismus) Hirschsprung s disease

6 486 O. CHEUNG & A. WALD DIAGNOSTIC TESTING FOR DEFECATION DISORDERS A number of diagnostic tests may be used to evaluate patients with possible defecation disorders. A barium or Gastrografin enema is appropriate when screening for structural abnormalities, such as megacolon/megarectum, as well as demonstrating the aganglionic distal bowel segment seen in classic Hirschsprung s disease. Anorectal manometry provides information on rectal sensation and compliance, reflexive relaxation of the internal anal sphincter and manometric patterns produced on attempted expulsion of the balloon apparatus. 6 During the latter manoeuvre, the rectal balloon provides some indication of the intra-abdominal pressures generated during expulsion efforts, whereas pressure recordings of the anal sphincters indicate relaxation or inappropriate contraction of the external anal sphincter. The presence of internal anal sphincter relaxation following rectal distension excludes Hirschsprung s disease from consideration. In patients with pelvic floor dyssynergia (also known as anismus), there is an increase in external sphincter pressure or failure to relax the external anal sphincter during attempted expulsion of the balloon. Also, these patients typically are unable to expel a 50-mL water-filled balloon within 60 s whilst seated on a commode. Pelvic floor dyssynergia appears to be an acquired disorder of defecation, as it may be reversed using behavioural techniques. Barium defecography provides a two-dimensional quantification of rectal parameters and functional information regarding the completeness of rectal emptying. Barium thickened to a consistency approximating stool is introduced into the rectum. 42 Evacuation of the barium is monitored by fluoroscopy or videotape whilst the patient sits on a specially constructed commode. Defecography has limited usefulness: normal parameters of an emptying of barium are broad, there is poor inter-observer agreement 43 and there is limited information of importance for clinical decision making. Neither balloon expulsion nor defecography duplicates defecation with its associated distal colonic propulsive activity, and the latter is performed in a public setting which may lead to behavioural inhibition. Colonic transit studies using radio-opaque markers are useful in patients with complaints of infrequent or difficult defecation in the setting of a colon of normal diameter. They are particularly useful when a pattern of slow transit with outlet delay is present, as this raises the possibility of a defecation disorder. In contrast, transit studies are usually unnecessary in patients with megacolon, as this indicates failed colonic propulsion which need not be characterized further. Neither the presence of normal colonic transit nor the delay of marker passage through the proximal colon excludes a defecation disorder. Patients with chronic idiopathic megacolon or megarectum have increased rectal compliance and elasticity, blunted rectal sensation and increased thresholds and smaller degrees of relaxation of the internal anal sphincter in response to rectal distension. In this disorder, propulsive forces are diminished and sensory signals which normally alert the individual to rectal filling are blunted. Rectocoeles are outpouchings of the rectovaginal wall into the lumen of the vagina. 44 Childbirth and excessive straining at defecation are known risk factors. Other suggested associated conditions are post-menopausal status, connective tissue disorders and hysterectomy. The relationship between rectocoeles and pre-existing defecatory dysfunction is unknown, that is, whether prolonged straining results in a rectocoele which, when it reaches a critical size, results in stool trapping and prolonged straining. What is clear is that most rectocoeles are asymptomatic, but that defecation difficulties may arise when expulsive forces are misdirected into a large pouch. TREATMENT OF DEFECATION DISORDERS Medical approaches Most patients with defecation disorders are successfully managed medically. Patients with a faecal impaction should be disimpacted, followed by daily enemas or the ingestion of polyethylene glycol solutions until colon cleansing is complete. If disimpaction is unsuccessful, a water-soluble contrast enema (Gastrografin) may be administered to eliminate retained stools. As with patients with overflow incontinence, an ongoing bowel management programme should be instituted. Following disimpaction and colon cleansing in demented or bedridden patients, a modified programme consisting of a fibre-restricted diet, together with cleansing enemas once or twice per week, will decrease the likelihood of recurrent faecal impactions. Enterokinetic drugs and laxatives are theoretically most appropriate in patients with constipation associated

7 REVIEW: MANAGEMENT OF PELVIC FLOOR DISORDERS 487 with slow gastrointestinal transit, whereas they may be less effective in patients with outlet dysfunction. However, there are no studies to confirm that this is so. A plausible approach in patients with both colonic and anorectal dysfunction would be to treat the former with laxatives or enterokinetic agents, whilst attempting to correct the latter with measures directed towards identifiable anorectal dysfunction (see below). There are a small number of reports concerning the injection of botulinum toxin into the anal sphincter for treatment of dyssynergic defecation. 45 In one study of four patients with pelvic floor dyssynergia who failed biofeedback, six units of botulinum toxin type A were injected bilaterally into the external anal sphincter or the puborectalis muscle. Although all patients reported improvement within 4 days after treatment, two reported symptomatic recurrence within 3 months. As yet, there is insufficient evidence for the use of botulinum toxin in patients with pelvic floor dyssynergia. Behavioural therapy biofeedback Biofeedback has been used in both controlled and (more often) uncontrolled studies and suggests promise as a treatment modality for patients with pelvic floor dyssynergia. 46, 47 Similar to biofeedback for faecal incontinence, various instruments, including anal electromyographic plugs and anorectal manometers, have been used to monitor external anal sphincter activity during expulsion efforts. The patient watches the recordings of electromyographic activity or sphincter pressure responses and is taught to modify inappropriate responses through trial and error. In one representative prospective study, a portable home device was used to reinforce initial training in the laboratory with an electromyographic instrument using both auditory and visual feedback. 48 Fifteen adult subjects with intractable constipation manifested by dyschezia were evaluated 3 and 6 months after completion of biofeedback training. Although pre- and postbiofeedback manometric findings were similar, the clinical index ( anismus index ) fell significantly after biofeedback and 13 patients were able to expel the rectal balloon (vs. two before biofeedback). Clinical improvement persisted during the 6-month follow-up period. As with most studies of biofeedback, the absence of a control group raises concern about potential bias. More recently, several controlled trials have been reported for adult patients. In one study, 11 patients received electromyographic biofeedback and nine received balloon biofeedback. 48 The results suggested that electromyographic biofeedback was more effective, with a success rate of 73%, compared with only 22% in the balloon group. Another study of 60 patients with intractable constipation compared the outcome of muscle training alone with the same training supplemented by an electromyographic recording visible to patients. 49 The outcomes were similar in the two groups, with a success rate of 43%. The authors concluded that muscle co-ordination training using personal instruction and encouragement without visual display may be a less complex but comparably effective treatment in an out-patient setting. As with biofeedback for faecal incontinence, the use of instrumental learning for defecation disorders remains unproven. Surgical approaches Treatment for patients with dyssynergic defecation was initially directed at the puborectalis muscle. Wasserman reported success in three of four patients following partial resection of the puborectalis muscle. 50 Wallace and Madden reported a similar success rate in 44 patients. 51 In contrast, Barnes et al. reported success in just two of nine patients, and five became incontinent to gas and liquid stool. 52 As a result, the use of surgery for patients with pelvic floor dyssynergia is strongly discouraged. The aim of surgical treatment for Hirschsprung s disease is to remove or bypass the aganglionic segment. The Soave endorectal pull-through procedure, Duhamel rectorectal pull-through procedure, Swenson rectosigmoidectomy and anorectal myectomy have been the most commonly used. The main advantage of the Soave procedure is that it minimizes the risk of pelvic nerve injury. 53 Long-term results in adults are generally good, although the incidence of post-operative complications, such as anastomotic disruption, is higher than that reported in children. The Duhamel procedure has a lower postoperative complication rate than the Soave procedure and avoids an extensive pelvic dissection. Long-term results are similar to those of the Soave procedure. The risk of post-operative constipation due to retained rectal septum or stenosis at the colorectal anastomosis has been reduced by the Martin modification. 54 The excellent results reported by Swenson have not been duplicated in adults by other surgeons, who reported a

8 488 O. CHEUNG & A. WALD 33% major complication rate, including 17% with impotence, with only an 80% long-term success rate. 53 Anorectal myectomy as an initial approach to adult Hirschsprung s disease has been advocated because of its low morbidity and technical ease of performance. Lynn and van Heerden suggested that patients in whom ganglion cells are found at the upper end of the myectomy may be considered to be cured, 55 but this was in contrast with the experience of McCready and Beart who reported that two of five patients who failed myectomy had ganglion cells at the proximal resection margin. 56 This makes it difficult to identify patients who require a myectomy only from those who would benefit from both myectomy and anterior resection. Long-term follow-up demonstrates poor results in 40% of patients who subsequently require further surgery. There appears to be no best surgical procedure for Hirschsprung s disease as the variety of procedures used and the varying skills of surgeons make it difficult to compare these methods. A successful outcome appears to depend as much on the surgeon s experience as on the procedure chosen. Within the last decade, open surgical correction of Hirschsprung s disease has been replaced by a laparoscopic approach in a number of centres. The indications for surgical repair of a rectocoele are not well defined, as surgery does not always improve symptoms. Furthermore, the size of the rectocoele does not seem to influence the surgical outcome. Van Laarhoven et al. reported the results of surgical repair of rectocoeles in 26 women with a median follow-up of 27 months. 57 Function was assessed by interview, anorectal manometry and evacuation proctography. Three-quarters of the patients improved symptomatically, with a significantly reduced feeling of incomplete evacuation (38 73%) and need to digitally assist evacuation (23 50%). Optimally, before a repair is entertained, one should demonstrate improved defecation when pressure is placed on the posterior wall of the vagina during defecation. Outcomes of surgical repairs for rectocoeles are difficult to evaluate because reported symptoms are heterogeneous and pre-operative investigations and surgical techniques are variable. There are no controlled studies comparing 58, 59 posterior colporrhaphy, trans-anal repair and repair with mesh augmentation, all of which seek to relieve symptoms and restore anatomy. Surgery may be considered in patients with megarectum if medical treatment fails. Surgical procedures advocated for the treatment of megarectum/colon include subtotal colectomy with ileorectal or ileosigmoid anastomosis, proctectomy with colo-anal anastomosis, pull-through procedures, Duhamel operation, anal myomectomy and restorative proctocolectomy. 60 It is crucial that patients be categorized accurately because colonic abnormalities determine surgical options. In patients with a moderately dilated colon, subtotal colectomy with ileorectal anastomosis offers the best results. If the entire colon and rectum are dilated, proctocolectomy with ileo-anal anastomosis is an alternative if anal sphincter function is normal; if not, ileostomy should be performed. Anorectal myectomy produces sub-optimal long-term results. 61 The use of the Soave or Swenson procedures remains controversial or anecdotal. Lateral puborectalis division for megarectum 62 or sympathectomy for megacolon 63 are to be discouraged. Antegrade colonic enemas Antegrade colonic irrigation via reversed appendicostomy was developed initially for the treatment of paediatric faecal incontinence and later was applied to constipation in children 64 and adults. 65 The premise of antegrade colonic enemas is that large-volume antegrade enemas produce complete colonic emptying to prevent faecal soiling. The best success rates have been achieved in patients with Hirschsprung s disease (91%), anorectal anomalies (89%) and spina bifida (84%). 66, 67 Fewer studies have assessed this procedure in the adult population. Hill et al. studied six adult patients with severe idiopathic constipation and associated pelvic floor weakness. All patients were able to evacuate the colon within 1 h of irrigation and none had appreciable incontinence. 65 In contrast, Gerharz reported that only eight of 16 adult patients with faecal incontinence were able to achieve a high degree of independence after antegrade colonic enema. 68 Reasons for failure included nausea, leakage, peristomal infection, abdominal cramps and phobia to catheterization. Antegrade colonic enemas may also be associated with a high burden of complications and surgical revisions. The incidence of stenosis in the literature ranges from 10% to 45% and is usually managed with repeated dilations. Other reported complications of antegrade colonic enemas include intestinal obstruction, caecal torsion and perforation during catheterization.

9 REVIEW: MANAGEMENT OF PELVIC FLOOR DISORDERS 489 ANAL FISSURES An anal fissure is a tear in the lining of the distal anal canal below the dentate line, occurring most commonly in the posterior midline. It can affect individuals of all ages and the incidence is equal in both sexes. 69 Clinical symptoms include anal pain during and after defecation, often accompanied by bright red rectal bleeding and pruritus ani. 70 Acute fissures have sharply demarcated fresh mucosal edges and may have granulation tissue in the base. When fissures fail to heal within 6 weeks, they are generally designated as chronic. 71 Chronic fissures have raised edges, characteristically exposing the horizontal fibres of the internal sphincter muscle at its base. Other findings associated with chronic fissures are external skin tags, hypertrophied anal papilla and, occasionally, anal stenosis. Pathogenesis of chronic fissures An understanding of the development of chronic anal fissures began with the observation that resting anal pressures are elevated in patients with anal fissures. 72 This observation was confirmed using manometry to measure the anal resting pressure in patients with chronic fissures. 73 These studies also demonstrated that sustained resting hypertonia was associated with abnormally few episodes of spontaneous internal anal sphincter relaxation. As the anoderm receives part of its blood supply from arterioles that cross the internal anal sphincter, it was hypothesized that elevated anal resting pressure could reduce perfusion to the anoderm and lead to local ischaemia. Doppler ultrasound techniques to measure blood flow in the anodermal area demonstrated that the posterior midline of the anal canal had the lowest perfusion of all four quadrants. 74 Subsequently, it was shown that lateral internal sphincterotomy normalized both elevated sphincter pressures and blood flow to the anodermal area in these patients. 75 Treatment of acute fissures More than 90% of acute anal fissures are short lived and heal with simple measures. High-fibre diet, stool softeners and warm sitz baths following bowel movements may provide symptomatic relief. Although topical anaesthetic creams have been used to relieve pain, there is evidence that they may delay healing when compared with bran supplements or topical hydrocortisone. 76 In a randomized trial comparing three treatments [sitz baths with bran supplement, 2% hydrocortisone cream only and 2% lignocaine (lidocaine) ointment only] in patients with acute posterior midline fissures, initial healing rates at 3 weeks were 88% for the sitz bath and bran group, 82% for the hydrocortisone group and 60% for the lignocaine (lidocaine) group. 77 Treatment of chronic fissures Chronic anal fissures are more difficult to treat and less than 10% will heal spontaneously or with the simple measures mentioned previously. Most available treatments are based on the premise that it is important to normalize anal sphincter hypertonia. Treatments which do so are divided into pharmacological and surgical modalities. Nitrates. Nitric oxide is the principal non-adrenergic, non-cholinergic neurotransmitter in gastrointestinal smooth muscle and mediates relaxation of the internal anal sphincter. 78 Glyceryl trinitrate is a donor of nitric oxide and has been shown to be effective in treating chronic anal fissures in several randomized, doubleblind, placebo-controlled trials. In one study, 80 patients with a chronic anal fissure were randomized to receive 0.2% topical glyceryl trinitrate or placebo. 79 After 8 weeks, healing with improvement of pain and reduction in maximum anal pressure occurred more often in the glyceryl trinitrate group (68%) than in the placebo group (8%). Similar results were obtained in another placebo-controlled randomized trial. 80 Another nitrate preparation, 1% isosorbide dinitrate ointment, was investigated only in a single uncontrolled study. 81 Isosorbide dinitrate ointment was applied every 3 h during waking hours in 34 patients with chronic anal fissure. The maximum anal pressures decreased and anodermal blood flow increased slightly at 3 and 6 weeks; 30 patients (88%) were healed at 12 weeks. The major side-effect was headache, which occurred commonly after 2 weeks of therapy. This incidence of headache was similar to that in a study which reported treatment-associated headaches in 58% of glyceryl trinitrate-treated patients and 18% of controls. Despite the beneficial results with topical nitrates, long-term follow-up has been lacking in many studies and there is no commercially available glyceryl trinitrate in the USA at the present time.

10 490 O. CHEUNG & A. WALD Calcium channel blockers. As smooth muscle contraction is mediated by increased cytosolic calcium levels, 82 blocking calcium channels can reduce internal anal sphincter tone. Several clinical trials have studied the use of topical calcium channel blockers in chronic anal fissures. Carapeti et al. applied 2% diltiazem gel to the anus to produce a 28% reduction in resting anal pressure. 83 This effect lasted for 3 5 h after a single application. A subsequent study by the same group showed that 67% of patients who were treated with 2% diltiazem gel three times daily were healed within 8 weeks and no patient reported headache. 84 Another randomized controlled trial compared oral (60 mg twice daily) and topical (2% gel twice daily) diltiazem in 50 patients with a chronic anal fissure. 85 Healing occurred in 38% of patients receiving the oral agent and 65% of those receiving topical therapy (P ¼ 0.09). Side-effects occurred in eight patients (33%) treated orally and in none treated topically. As yet, there has been no trial comparing topical nitrates with topical calcium channel blockers. Botulinum toxin. This is a potent inhibitor of acetylcholine release from nerve endings and has been used successfully to treat spastic disorders of skeletal muscle, as well as those involving gastrointestinal smooth muscle. 86 In a randomized placebo-controlled study, 30 patients with chronic anal fissure received two injections of botulinum toxin (20 units into the internal anal sphincter) or saline injection. 87 After 2 months, patients who received botulinum toxin showed significantly higher healing rates (73% vs. 13%). Four patients in the botulinum toxin arm who did not heal were re-treated and all healed within 2 months. One patient experienced transient incontinence to flatus after botulinum toxin injection. No recurrences were observed at 16 months of follow-up. Botulinum toxin (20 units injected into the internal anal sphincter on each side of the anterior midline) was also compared with topical glyceryl trinitrate (0.2% b.d.) in a randomized trial of 50 patients with chronic anal fissure. 88 Healing rates were significantly higher in the botulinum toxin group (96% vs. 60%), and resting anal pressures decreased to a greater extent in the botulinum toxin group than in the glyceryl trinitrate group (29% vs. 14%) at 2 months. Approximately 20% of patients in the glyceryl trinitrate group reported moderate to severe headaches associated with treatment, but no side-effects were noted in the botulinum toxin group. Other agents. Small studies of muscarinic agonists and b-adrenergic agonists suggest that such agents hold promise as alternative treatments for chronic anal fissures. One study of 10 healthy volunteers reported a 24% reduction in resting anal pressure with 0.1% bethanechol gel. 83 In another study, nine of 15 patients with chronic anal fissure (60%) healed after treatment with 0.1% bethanechol gel applied three times daily. 84 The mean resting pressure decreased by 16% with treatment and no side-effects were reported. A single oral 20-mg dose of indoramin, an a 1 - adrenoreceptor inhibitor, was investigated in six healthy volunteers and seven patients with chronic anal fissure. Resting anal pressures decreased to a similar extent (36 40%) in both groups. 89 However, a randomized controlled trial of indoramin vs. placebo was stopped due to a low healing rate in the indoramin group. 90 Surgery. Surgery is often reserved for patients with persistent symptoms who have failed medical therapy. The most common procedure is lateral internal anal sphincterotomy, involving division of the internal anal sphincter from its most distal end for a distance equal to that of the fissure, or to the dentate line. More than 90% of patients heal after lateral internal anal sphincterotomy and recurrence rates of anal fissures are between 0 and 25%. 91 The most important determinant of outcome appears to be the extent of sphincterotomy. One study used anal ultrasonography to show a high rate of incomplete sphincterotomy in those patients who developed symptomatic recurrences. 92 Open and closed techniques produce similar reductions of anal pressure 93, 94 and rates of healing. The major concern with lateral internal anal sphincterotomy is the development of faecal incontinence. Approximately 45% of patients experience some degree of incontinence immediately after surgery flatus (31%), mild faecal soiling (39%) and gross incontinence (23%). However, only 6% reported incontinence to flatus, 8% had minor faecal soiling and 1% experienced loss of solid stool 5 years after surgery. 91 FUNCTIONAL PROCTALGIA DISORDERS Anorectal pain (proctalgia) has been described in association with a variety of organic conditions, but also occurs in patients in whom organic conditions are not identified, and the pathophysiology is poorly

11 REVIEW: MANAGEMENT OF PELVIC FLOOR DISORDERS 491 understood. The two common functional disorders levator ani syndrome and proctalgia fugax are distinguished by the duration and frequency of painful episodes, and by the absence of physical findings in asymptomatic patients with proctalgia fugax. Levator ani syndrome must also be distinguished from other disorders of chronic anorectal pain (e.g. coccygodynia, rare genetic syndromes of familial rectal pain, tumours of the pelvis or cauda equina, endometriosis and other gynaecological causes of chronic pain). 95 In both of these poorly understood entities, reports of effective therapy are largely anecdotal and therapeutic modalities have not been examined rigorously with controlled trials. Levator ani syndrome The diagnosis of levator ani syndrome is made by the clinical history, physical examination and exclusion of other disorders that can produce chronic proctalgia. The pain in levator ani syndrome is described as a dull or pressure-like discomfort in the rectum which lasts for several hours or longer. Both prolonged sitting and defecation often precipitate the pain; in addition, symptoms of difficult defecation or a sense of incomplete evacuation have been described. 96, 97 A common clinical finding is palpable tenderness of overly contracted levator ani muscles as the examining finger moves from the coccyx posteriorly to the pubis anteriorly. The tenderness is often asymmetric and is most commonly found on the left. 96 It has been estimated that 6 7% of the general population have symptoms consistent with levator ani syndrome, but only 29% of affected individuals consult a physician. 95 In one report, 12% of patients with levator ani syndrome also reported having proctalgia fugax. 96 An international committee has proposed diagnostic criteria, consisting of chronic or recurrent episodes of rectal pain or aching lasting for 20 min or longer for at least 3 months in the absence of other causes, such as ischaemia, inflammatory bowel disease, cryptitis, intersphincteric abscess, anal fissure, haemorrhoids and coccygodynia. 97 Levator ani syndrome is highly likely if posterior traction of the puborectalis reveals contracted levator ani muscles and tenderness is elicited, whereas the diagnosis is considered possible if symptoms occur in the absence of physical findings. Treatment has often been directed towards the reduction of anal canal and/or levator ani muscle tension. Digital massage, in which the levator ani muscles are massaged to tolerance three to four times per week, has been practised since a favourable report was published in 1936, 98 although others did not confirm this. 99 Sitz baths of 40 C have been reported to reduce anal canal pressures in patients with levator ani syndrome. 100 Although the efficacy of sitz baths is uncertain, they appear to be harmless. The use of muscle relaxants, such as diazepam and methocarbamol, together with massage and sitz baths, has been reported to be effective, 96 although not by all. 100 Mechanical devices, such as electrogalvanic stimulation delivered via a rectal probe for approximately 15 min, resulted in an 80 90% 101, 102 improvement rate in previously untreated cases, but only a 25% improvement rate in patients who had failed other treatments. 103, 104 Biofeedback using pressure-measuring probes or electromyographic recording devices produced improvement rates ranging from 43% to 100%, associated with decreased anal canal pressure 105, 106 or electromyographic activities. None of these studies was controlled and the best that can be said about these treatments is that they help many patients and do no harm. Surgical treatment with surgical division of the puborectalis muscle is not recommended because of the high incidence of incontinence for liquid or gas associated with it. 107 Proctalgia fugax Proctalgia fugax is characterized by sudden episodic, severe pain in the rectal area that lasts for several seconds or minutes before disappearing completely. The pain has been described as aching, gnawing, cramping or stabbing. In contrast with levator ani syndrome, patients who are asymptomatic during examination exhibit no characteristic physical findings. As a result, the diagnosis relies entirely on the clinical description and the exclusion of other diseases that can produce proctalgia. In one survey, about 14% of a healthy population reported at least one episode of proctalgia fugax and 5% reported having at least six episodes yearly. Less than 20% of affected individuals had sought medical attention. 108 The pathophysiology of the pain in proctalgia fugax is unknown. Early reports of anal sphincter spasm or contractions of the puborectalis and external anal sphincter muscles have never been substantiated. 109 An autosomal-dominant inherited myopathy of the internal anal sphincter associated with both proctalgia