Faecal incontinence
Authors: M. A Kamm
Journal: BMJ (2003)

Faecal incontinence, not a glamorous area of medicine, has changed markedly in its recognition and management over the past 10 years. Patients and doctors can talk about it now as the taboo is disappearing. Pathophysiology is better understood, helped by advances in imaging. Treatments are improving as they move away from invasive sphincter surgery as an early step to the use of simple pharmacological treatments, behavioural techniques, injectable biomaterials, and, when necessary, minimally invasive surgery.

Faecal incontinence affects both sexes and all age groups. Approximately 2% of the adult population have it on a frequent basis.1 The commonest cause of faecal leakage is probably degeneration of the delicate smooth muscle of the internal anal sphincter—the muscle that maintains sphincter closure.2 The commonest cause in young women is obstetric anal sphincter damage. Most sphincter damage is occult; approximately a third of first vaginal deliveries result in endosonographically identifiable structural sphincter damage; about a third of these are associated with new bowel symptoms of faecal incontinence or urgency.3 Forceps delivery is the greatest risk factor; others are a large baby, occipito-posterior position, and a prolonged second stage of labour. The same risk factors apply to the 1% of vaginal deliveries complicated by a recognised third degree tear.4

Structural damage to the sphincter can also result from surgery. This may be an unavoidable consequence of necessary treatment such as in the care of an anal fistula. Or it may result from anal dilatation, an outmoded form of treatment for chronic fissure or constipation.

In elderly people, especially those in care, faecal impaction is a common cause of leakage. Many factors contribute to this process, including constipating medications and poor mobility.5 Children with faecal impaction leak stool. Others have impaired continence after correction of congenital anorectal abnormalities.

A complete history, examination for sphincter damage or faecal impaction, and correction of predisposing factors, can lead to successful treatment in many patients. If further investigation is required anal endosonography has become the standard means of imaging the anal sphincter, and is now available in most specialist centres.6 It enables identification of structural damage and degenerative disorders of the sphincter muscles. When sepsis involves the sphincter complex, such as in complex perianal fistulas or Crohn's disease, magnetic resonance imaging provides accurate information.

Factors contributing to continence include the integrity of the sphincter muscles, the force of bowel contraction, consistency of stools, and cognitive factors. Each of these can act as a suitable target for treatment. Most commonly a combination of treatments is useful. For example, for patients with urge faecal incontinence, learning to overcome a sense of panic, sustain contraction of the sphincter, and titrate loperamide can lead to marked improvement in the symptom sometimes even when there is structural damage to the sphincter.7

Drugs that diminish the force of bowel contractions and enhance absorption of luminal colonic water can transform bowel control and the ability to function socially. Loperamide is effective in patients with symptoms of either urgency or leakage. The wide therapeutic to toxic ratio makes this a very safe drug in adults and one that should be titrated to achieve control of symptoms. If one capsule is too constipating patients can use smaller doses of the syrup formulation.

Topical application to the perianal skin is an alternative pharmacological approach. Topical phenylephrine, which increases the tone of the sphincter smooth muscle, is under development.8

Behavioural techniques have transformed the management of this condition.9 Even in patients with structural damage it is often possible to improve continence substantially, which implies that there is often an element of reversibility and that a complex combination of factors contributes to continence.7,9

A recent randomised study examined which component of behavioural treatment was most important.7 Treatment with bowel focused counselling, including advice on resisting urgency and titrating loperamide, was as effective as providing the patient with real time feedback—biofeedback—about sphincter function. The pharmacological treatment, advice, and nature of the interaction between therapist and patient seemed to be more important than the technical aspects of treatment.

In institutionalised elderly patients a combination of treatments is most likely to be fruitful, including attention to medications, regular toileting, and sometimes use of gentle laxatives.5 When non-invasive treatments have failed minimally invasive treatments can be considered. Injection of silicone biomaterial can improve leakage caused by a weak internal anal sphincter.10 Surgery should be reserved for patients with major incontinence that has failed to respond to conservative treatment and is necessary in only very few patients. However, no operation is capable of restoring the sphincter to its original finely tuned state.

An overlap repair of the sphincter is still the first line surgical treatment for major disruption of the sphincter due to obstetric causes, especially if there is loss of the perineal body. However, although the short term results are good, the long term results are less satisfactory.11

More invasive procedures include the artificial bowel sphincter or repositioning the gracilis muscle as a neo-sphincter around the anal canal.12 Both operations have a substantial learning curve, a success rate of about 50% in good hands, and are associated with considerable morbidity. Another treatment undergoing evaluation is radiofrequency ablation at the anorectal junction, a process that may induce fibrosis and prevent neurally mediated sphincter relaxations.

An alternative to sphincter surgery entails modulating the neural control of the lower bowel and sphincter. Chronic low amplitude stimulation of sacral nerves, via percutaneously inserted fine wire electrodes, is substantially less invasive than sphincter surgery and has proved successful.13

The socially disabling symptom of faecal incontinence is usually amenable to simple and inexpensive treatments. General practitioners need to be familiar with the condition, initiate treatment, or obtain help from continence advisers. Surgeons need to exhaust conservative treatments before proceeding to surgery and be realistic about the outcome of surgery. Healthcare providers need to establish multiskilled regional centres offering a range of diagnostic and treatment expertise.