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Biofeedback for anismus

Clinical bottom line: There is no compelling evidence for biofeedback in the treatment of anismus. No placebo controlled, double blind trials were available at the time this review was conducted. Better quality randomised, blind trials are required to assess the efficacy and long-term safety of biofeedback.

Anismus is one of the commonest causes of chronic constipation. Biofeedback is thought to be helpful because it involves learning through reinforcement of the visceral organs and functions. This may relax the muscles.

Systematic review:

Ernst E, Resch KL. A meta-analysis of biofeedback treatment for anismus. Eur J Phys Med 1995; 5(5):157-159.

Date review completed: 1994

Number of trials included: 11

Number of patients: 177 total

Control groups: pre-treatment control phase; use of laxatives; dietary regimes.

Main outcomes: percent of patients with relevant improvement.

Inclusion criteria were controlled clinical trial; assessment of biofeedback for relief of anismus. MEDLINE (1980-1994) was searched for clinical trials on biofeedback, constipation and anismus. Reference lists of retrieved reports were also checked. Information from studies which reported the number or proportion of patients improved was pooled in a meta-analysis.


Eleven studies were included; none were double blind or used a placebo control. All were small. In the individual trials, average duration of anismus ranged between 3-27 years (three studies did not mention this) and the average age of patients varied between 7-68 years. Length of follow-up was between none-14 months in most studies and 2-4.5 years in one. The endpoints used in the trials were number of defecations following biofeedback, use of laxatives, change in symptoms of constipation. All studies were positive; 93/137 (68%) patients improved. One showed electromyography (EMG) to be superior to manometry; 87/106 (82%) patients improved with EMG.

Adverse effects

The reviewers stated that the long-term safety of biofeedback is not known.



The reviewers' commented on the consistency of the results across studies despite the differences in trial design (e.g. variations in the type of intervention, number of treatment sessions, type of constipation, duration of follow-up). The use of cross-over design also means that carry over effects cannot be ruled out (e.g. if laxatives are used). Whether the response rate of 68% was due to biofeedback or a strong placebo effect cannot be determined because no study used a placebo group. The possibility of bias arises because of the lack of blinding. There was no mention of whether studies randomised patients to treatment groups. Large, randomised, blind, placebo controlled trials are required to assess whether biofeedback is effective and safe. Blinding can be achieved by using sham-biofeedback techniques. One study showed biofeedback (88% patients improved) to be superior to conventional treatment (47% patients improved) in children. However, there were only 13 patients per group.

Further reading

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