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Imperforate anus

An imperforate anus or anal atresia is a birth defect in which the rectum is malformed. Its cause is unknown. more...

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Features

There are several forms of imperforate anus:

A low lesion, in which the colon remains close to the skin. In this case, there may be a stenosis (narrowing) of the anus, or the anus may be missing altogether, with the rectum ending in a blind pouch.
A high lesion, in which the colon is higher up in the pelvis and there is a fistula connecting the rectum and the bladder, urethra or the vagina.
A cloaca (named after the analogous orifice in amphibians), where the rectum, vagina and colon are joined into a single opening.

Imperforate anus usually presents along with other birth defects—spinal problems, anal atresia, heart problems, tracheoesophageal fistula, esophageal atresia, renal anomalies, and limb anomalies.

Treatment

Imperforate anus usually requires immediate surgery to open a passage for faeces. Depending on the severity of the imperforate, it is either treated with a perineal anoplasty or colostomy.

Prognosis

With a high lesion, many children have problems controlling bowel function and most also become constipated. With a low lesion, children generally have good bowel control, but they may still become constipated.

Epidemiology

Imperforate anus has an estimated incidence of 1 in 5,000 live births. It is more common in boys than in girls.

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Faecal incontinence - Fortnightly Review
From British Medical Journal, 2/14/98 by Michael A. Kamm

Faecal incontinence affects men and women of all ages. Daily or weekly episodes occur in about 2% of the adult population and in about 7% of healthy independent adults over the age of 65.[1-4] The disorder causes great personal disability and has a high financial cost. In the United States, more than $400m each year is spent oil faecal incontinence appliances alone, and faecal incontinence is the second commonest reason (more common than dementia) for requesting placement in a nursing home.[5] A third of elderly people in retirement homes or hospital are incontinent for stool.

Issues related to faecal incontinence are especially relevant with a growing population of elderly people. Advances in understanding and treatment have led to improved treatments and a good outcome for most patients. Much progress has been brought about by the recent development of accurate and simple techniques for imaging the anal sphincter muscles.

This review focuses oil advances in the understanding and treatment of faecal incontinence. It is not a systematic review but is based on a choice of areas that I feel are of greatest recent importance, supplemented by a Medline search using the keywords "faecal incontinence."

Symptoms, clues, and investigations

Passive faecal incontinence or soiling--that is, faecal leakage without awareness--is usually associated with dysfunction of the smooth muscle tissue of the internal anal sphincter or with impacted stool in the rectum. Faecal urgency and urge incontinence are generally related to dysfunction of the striated muscle tissue of the external anal sphincter or to high bowel pressures and a normal sphincter, seen in patients with irritable bowel syndrome or diarrhoea from other causes.[6]

Advances in sphincter imaging and physiological testing

The introduction of anal endosonography as a way of imaging accurately the anal sphincter muscles has enabled accurate identification of the lesions causing faecal incontinence and has allowed rational planning of treatment. Magnetic resonance imaging with an anal coil can be helpful in investigating para-anal structures or when the ultrasound findings are equivocal.

Endosonography has largely replaced electromyography, although the latter may be useful when scarring makes interpretation of ultrasonography difficult or in patients who have had an imperforate anus. Pudendal nerve latency testing is less valuable than was previously believed, as most patients have identifiable structural damage or muscle degeneration rather than neuropathy.

Clinical presentation

Faecal incontinence after childbirth

Structural damage to the anus and new bowel symptoms are common after vaginal delivery.[7] Anal enclosonography has shown that 30% of women have occult structural damage affecting one or both anal sphincter muscles after their first vaginal delivery.[8] Around a third of these women develop anal incontinence or urgency. Incontinence is usually for gas, but in a few women it is for solid or liquid stool. Of the 0.5% to 1% of women who have a recognised third degree tear during vaginal delivery, 85% have residual structural sphincter damage and half of these have symptoms despite a primary repair at the time of delivery.[9] The commonest risk factors for damage during childbirth are the use of forceps, a large baby, a long second stage of labour, and occipitoposterior presentation of the fetus.

Occult anal sphincter damage can exist even though the perineum is intact, and digital examination may be misleading about muscle strength and sphincter integrity.[10] For these reasons manometric assessment of function, together with endosonographic assessment of structure, is necessary to identify the abnormality.

Faecal incontinence after surgery

In a referral centre, sphincter damage after anal surgery is the commonest cause of incontinence after obstetric trauma. Incontinence may be unavoidable--for example, after complex anal fistula surgery. It may also occur as an unexpected complication of a simple operation--for example, after internal anal sphincter damage during haemorrhoidectomy (figs 1 and 2). Lastly, incontinence may occur when the sphincter is divided as part of' surgical treatment-for example, after division of the lower internal anal sphincter in chronic anal fissure. In one series of 829 patients who had a sphincterotomy for chronic anal fissure, 35% had lack of control for flatus, 22% soiled, and 5% had major episodes of incontinence.[11] The recent finding that treatment with topical glyceryl trinitrate or other nitric oxide donors can lower anal pressure and cause fissure healing suggests that pharmacological therapies will become first line treatment for chronic anal fissure.[12 13]

[Figures 1 and 2 ILLUSTRATION OMITTED]

Internal sphincter dysfunction

Structural damage is the commonest cause of sphincter weakness[14]; where this is absent, isolated degeneration of the smooth muscle of the internal anal sphincter is the commonest cause of soiling.[15] This condition affects both men and women, often in middle age. The resting anal pressure is low, and endosonography often shows that the internal sphincter is thin and fibrotic. Pudendal nerve damage, previously believed to be responsible for most cases of idiopathic faecal incontinence, is rare. Weak or structurally damaged smooth muscle tissue of the internal anal sphincter cannot be treated surgically. Most of these patients respond to treatment with loperamide.

Patients with progressive systemic sclerosis[16] or chronic idiopathic intestinal pseudo-obstruction, and those who have had radiotherapy for cervical or other pelvic neoplasms, may develop degeneration and fibrosis of the internal anal sphincter leading to passive faecal incontinence. The problem is sometimes compounded by diarrhoea.

Neurological disease

Many patients with neurological disease have faecal incontinence that may impair their quality of life as much as the primary disorder. In these patients, any non-neurological components such as damage during childbirth, side effects of drugs, or coexistent behavioural disorders need to be identified.

Faecal incontinence occurs in about 50% of patients with multiple sclerosis, and in 25% it occurs at least weekly.[17] In a series of patients with spinal injuries, 61% had faecal incontinence, and in 11% it occurred at least weekly.[18] Patients rated their bowel symptoms not far below the loss of mobility in terms of distress. Faecal incontinence also occurs in patients with long-standing neuropathy secondary to diabetes mellitus.

Congenital disorders

Faecal incontinence is a major social disability in 90% of patients with spina bifida, and about 50% soil regularly.[19] Bowel programmes with regular bowel evacuation triggered, by reflex can lead to improved continence in some.[20] We are now seeing the long term results of surgery in infancy or childhood for congenital disorders. Incontinence occurs in 50% to 80% of adolescents and adults treated for anal arrears,[21] regardless of the whether the operation was a posterior sagittal anorectoplasty or a "pull through" procedure.[22] Faecal incontinence can be a considerable source of distress; in one study 20-30% of 160 children and adolescents with congenital malformations had emotional problems.[23] In 60 children who had been operated on for Hirchsprun's disease a mean of nine years previously, 53% had serious faecal soiling and 27% less severe soiling, and the prevalence did not seem to decrease with age.[24]

Disorders in children and adolescents

Children with a normal anal sphincter can pass stool inappropriately (encopresis), or they may leak faeces as a result of faecal impaction with overflow, which usually requires disimpaction and treatment with laxatives. When laxatives are used as the main treatment, biofeedback does not offer additional benefit,[25] but it may be a useful alternative primary treatment. Biofeedback aims to teach the patient pelvic floor coordination and also incorporates disciplined toileting behaviour. In one study, almost half the children who had failed with laxative treatment recovered with bopfeedback.[26] Constipation in most children will resolve with time, but a small group with a widely dilated rectum and recurrent faecal impaction remain constipated as adolescents and young adults. While the cause may be behavioural in some of these children, others may have a poorly defined neuromuscular disorder of the distal gut. They require faecal disimpaction and long term laxative treatment.[27]

Advances in surgical treatment

Simple surgical repair

Many patients with a single sphincter tear from obstetric trauma, and some with discrete damage from other types of injury such as motor accidents and after fistula surgery, can be cured by surgical repair. In 80% of patients with obstetric damage, anterior overlap repair of the external sphincter resolves symptoms, and benefit is seen in middle aged women as well as those who present soon after childbirth.[30]

Complex surgery

Muscle transposition--When the anal sphincter muscles are damaged irreparably, other striated muscles such as the gracilis or gluteus can be surgically "wrapped" around the anal canal to increase resting tone. The most tested of these operations is the gracilis neosphincter, which requires chronic electrical stimulation to maintain active muscle contraction. In a study of 52 patients, 73% were continent after a median follow up of two years. The procedure was associated with improved bowel frequency, ability to postpone defecation, less anxiety, and improved quality of life.[31] the gracilis neosphincter has also been used in patients undergoing abdominoperineal excision for low rectal cancer. The continence rate after this procedure is high, although the complication rate in one series was approximately 401%.[32] The operation has a high failure rate in patients with congenital abnormalities, probably because these patients have abnormal hind gut function. Although die gracilis neosphincter procedure has good results in expert hands,[31] the learning curve for surgeons is steep and the operation is associated with many pitfalls and high morbidity.[33]

Artificial sphincter--An alternative to the use of transplanted striated muscle is a synthetic sphincter device. This consists of a silastic inflatable cuff, a valve which allows the cuff to deflate for a few minutes for the purpose of defecation, and a reservoir (fig 3). The artificial urinary sphincter has been implanted around the anal canal, but a purpose designed anal device is currently undergoing evaluation. These devices may be best for patients with anal leakage, rather than those with faecal urgency and high bowel pressures.

[Figure 3 ILLUSTRATION OMITTED]

Sacral nerve stimulation--Electrical stimulation of sacral nerve roots has been reported to restore continence in patients with structurally intact muscles.[34] An electrode inserted into the S3 sacral foramen provides low grade stimulation via a chronic stimulator implanted under the anterior abdominal wall. This technique does not stimulate the motor nerves sufficiently to cause contraction, but it is thought to act by facilitating sphincter contraction and changing the sacral reflexes.

Antegrade colonic irrigation--Some patients with extensive sphincter damage, neurological disease, previous anorectal abnormalities, spina bifida, or sacral agenesis have poor control over bowel function. Daily enemas to empty the distal bowel, followed by loperamide to prevent soiling, are sometimes effective, but if they are not, colonic emptying can be achieved by antegrade colonic irrigation. The appendix is brought out to the skin and is used for catheter entry--the so called antegrade continence enema (ACE) procedure. This technique has been used mainly in children, and although it is effective initially, long term problems include stenosis, the need for refashioning, and resistance to laxative or irrigation.[35] An alternative means of antegrade colonic irrigation is via a transverse colonic conduit incorporating an intussusception valve and cutaneous aperture.[36]

Colostomy--When other surgical measures have failed or are inappropriate and the patient has uncontrolled incontinence, the creation of a colostomy can still provide major benefit to some.

Advances in non-surgical treatment

Drugs

When symptoms are mild, infrequent, and not due to impaction with overflow, treatment with loperamide or codeine phosphate is safe and often very effective. These drugs can benefit patients with soiling or passive leakage and those with urge incontinence. Loperamide is safe, can be titrated to achieve relief of symptoms, and can be used as required or continuously. Both drugs reduce motility of the large bowel and increase absorption, making the stool more formed.

Direct sphincter electrical stimulation

Although anecdotal reports about direct transcutaneous electrical stimulation of the sphincter have been positive, there are no studies in which the cause of incontinence has been well defined and patients have been followed up for a long period. Given the success of this treatment in urinary incontinence, however, it deserves further evaluation.

Biofeedback for faecal incontinence

Similar criticisms can be levelled at die studies on biofeedback retraining. Most of the 40 published studies describing the results of pelvic floor biofeedback for faecal incontinence suggest an improvement rate of 60-70%.[37] However, selection criteria were poor, the sphincter abnormalities not well defined, and the follow up periods short. Biofeedback aims to condition patients to be more sensitive to a stimulus distending the rectum and to heighten the voluntary striated muscle sphincter response, with the patient watching or listening to a feedback signal of the level of external sphincter contraction. We do not yet know which patients respond best to this type of treatment.

Behavioural retraining

In intellectually disabled people, a behavioural programme with prompted sitting on the lavatory, rewards for evacuation, and attention to stool consistency using fibre supplements or a bulking agent can produce "normal" bowel function.[38]

Conclusion

An awareness of the high prevalence and predisposing factors for the development of faecal incontinence, together with a multidisciplinary approach to treatment, can lead to relief from this distressing symptom in most patients.

[1] Denis P, Bercoff E, Bizien MF, Brocker P, Chassagne P, Lamouliatte H, et al. Etude de la prevalence de l'incontinence anale chez l'adulte. Gastroenterol Clin Biol 1992;16:344-50.

[2] Nelson R, Norton N, Cautley E, Furner S. Community-based prevalence of anal incontinence. JAMA 1995;274:559-61.

[3] Talley NJ, O'Keefe FA, Zinsmeister AR, Melton JL. Prevalence of gastrointestinal symptoms in the elderly: a population based study. Gastroenterology 1992;102:895-901.

[4] Johanson JJ, Lafferty J. Epidemiology of fecal incontinence: the silent affliction. Am J Gastroenterol 1996;91:33-6.

[5] Lahr CJ. Evaluation and treatment of incontinence. Practical Gastroenterol 1988; 12:27-35.

[6] Engel AF, Kamm MA, Bartram CI, Nicholls RJ. Relationship of symptoms in faecal incontinence to specific sphrincter abnormalities. Int J Colored Dis 1995;10:152-5.

[7] Kamm MA. Obstetric damage and faecal incontinence. Lancet 1994;344:730-3.

[8] Sultan AH, Kamm MA, Hudson CN, Bartram CI. Anal sphincter disruption during vaginal delivery. N Engl J Med 1993;329:1905-11.

[9] Sultan AH, Kamm MA, Bartram CI, Hudson CN. Third degree obstetric anal sphincter tears: risk factors and outcome of primary repair. BMJ 1994;308:887-91.

[10] Sultan AH, Kamm MA, Talbot IC, Nicholls RJ, Bartram GI. Anal endosonography for identifying external sphincter defects confirmed histologically. Br J Surg 1994;81:463-5.

[11] Khubchandani IT, Reed JF. Sequelae of internal sphincterotomy for chronic fissure in ano. Br J Surg 1989;76:431-4.

[12] Loder PB, Kamm MA, Nicholls RJ, Phillips RKS. Local application of a nitric oxide donor (glyceryl trinitrate) reduces anal resting tone: therapeutic implications. Br J Surg 1994;81:1386-9.

[13] Lund JN, Scholefield JH. A randomised, prospective, double-blind, placebo-controlled trial of glyceryl trinitrate ointment in the treatment of anal fissure. Lancet 1997;349:11-4.

[14] Burnett SJD, Spence-Jones C, Speakman CTM, Kamm MA, Hudson CN, Bartram CI. Unsuspected sphincter damage following childbirth revealed by anal endosonography. Br J Radiol 1991;64:225-7.

[15] Vaizey C, Bartram CI, Kamm MA. Primary internal anal sphincter degeneration. A previously unrecognised cause of passive faecal incontinence. Lancet 1997;349:612-5.

[16] Engel A, Kamm MA, Talbot IC. Progressive systemic sclerosis of the internal anal sphincter leading to passive faecal incontinence. Gut 1994;35:857-9.

[17] Hinds JP, Eidelman BH, Wald A. Prevalence of bowel dysfunction in multiple sclerosis. Gastroenterology 1990;98:1538-42.

[18] Glickman S, Kamm MA. Bowel dysfunction in spinal cord injury patients. Lancet 1996;347:1651-3.

[19] Malone PS, Wheeler RA, Williams JE. Continence in patients with spina bifida: long term results. Arch Dis Child 1994;70:107-10.

[20] King JC, Currie DM, Wright E. Bowel training in spina bifida: importance of education, patient compliance, age, and anal reflexes. Arch Phys Med Rehabil 1994;75:243-7.

[21] Hassink EA, Rieu PN, Severijnen RS, Brugman-Boezeman AT, Festen C. Adults born with high anorectal atresia--how do they manage? Dis Colon Rectum 1996;39:695-9.

[22] Mulder W, de Jong E, Wauters I, Kinders M, Heij HA, Vos A. Posterior sagittal anorectoplasty: functional results of primary and secondary operations in comparison to the pull-through method in anorectal malformations. Eur J Paediatr Surg 1995;5:170-3.

[23] Ludman L, Spitz L, Kiely EM. Social and emotional impact of faecal incontinence after surgery for anorectal abnormalities. Arch Dis Child 1994;71:194-200.

[24] Catto-Smith AG, Coffey CM, Nolan TM, Hutson JM. Fecal incontinence after the surgical treatment of Hirschsprung's disease. J Pediatr 1995;127:954-7.

[25] Van der Plas RN, Benninga MA, Buller HA, Bossuyt PM, Akkermans LMA. Redekop WK, et al. Biofeedback training in treatment of childhood constipation: a randomised controlled study. Lancet 1996;348:776-8.

[26] Loening-Baucke V. Persistence of chronic constipation in children after biofeedback treatment. Dig Dis Sci 199 1;36:153-60.

[27] Gattuso JM, Kamm MA. Clinical features of idiopathic megarectum and idiopathic megacolon. Gut 1997;41:93-9.

[28] Madden MV, Kamm MA, Nicholls RJ, Santhanam AN, Cabot R, Speakman CTM. Abdominal rectopexy for complete prolapse: a prospective study evaluating changes in symptoms and anorectal function. Dis Colon Rectum 1992;35:48-55.

[29] Engel AF, Kamm MA, Bartram CI. Unwanted anal penetration as a physical cause for faecal incontinence. Eur J Gastroenterol Hepatol 1995;7:65-7.

[30] Engel AF, Sultan AH, Kamm MA, Bartram CI, Nicholls RJ. Anterior sphincter repair for patients with obstetric trauma. Br J Surg 1994;81:1231-4.

[31] Baeten CGMI, Geerdes BP, Adang EMM, Heineman E, Konsten J, Engel GL, et al. Anal dynamic graciloplasty in the treatment of intractable fecal incontinence. N Engl J Med 1995;332:1600-5.

[32] Cavina E. Outcome of restorative perineal graciloplasty with simultaneous excision of anus and rectum for cancer. A ten year experience with 81 patients. Dis Colon Rectum 1996;39:182-90.

[33] Wexner SD, Gonzalez-Padron A, Rius J, Teoh T-A, Cheong DM, Nogueras JJ, et al. Stimulated gracilis neosphincter operation. Initial experience, pitfalls, and complications. Dis Colon Rectum 1996;39:957-64.

[34] Matzel KE, Stadelmaier U, Hohenfellner M, Gall FP. Electrical stimulation of sacral spinal nerves for treatment of faecal incontinence. Lancet 1995;346:1124-7.

[35] Griffiths DM, Malone PS. The Malone antegrade continence enema. J Paediatr Surg 1995;30:68-71.

[36] Hughes SF, Williams NS. Continent colonic conduit for the treatment of faecal incontinence associated with disordered evacuation. Br J Surg 1995;82:1318-20.

[37] Erick P. Biofeedback naming in disordered defaccation: a critical review. Dig Dis Sci 1993;38:1953-60.

[38] Smith LJ, Franchetti B, McCoull K, Pattison D, Pickstock J. A behavioural approach to retraining bowel function after long-standing constipation and faecal impaction in people with learning disabilities. Dev Med Child Neurol 1994;36:41-9.

(Accepted 28 August 1997)