Biofeedback therapy has been reported to be an effective treatment for functional anorectal disorders such as functional constipation and functional fecal incontinence over the past few decades.2,27
Biofeedback therapy has been accepted as the treatment of choice for pelvic floor dyssyndergia and fecal incontinence due to its clinical efficacy. However, there continues to be controversies regarding its efficacy. First, most of the clinical findings were found to be based on the uncontrolled studies. In addition, many of the studies had methodological limitations, such as the differences in the criteria used to define successful outcome, the heterogeneity of the participants studied, and the different variables considered during the assessments. Furthermore, some studies did not show biofeedback therapy to be more effective than conservative treatments especially in patients with fecal incontinence22,23
and childhood functional constipation.28
However, the more important issue would be about the effects of biofeedback therapy to be maintained or not. As biofeedback therapy is a relatively inexpensive and non-invasive modality, it could be considered as the first-line therapy in patients with refractory anorectal disorders when its efficacy is predicted to be maintained for a long time interval.
Constipation could be classified into normal-transit constipation, pelvic floor dyssynergia, slow-transit constipation, and the mixed type according to the results of physiological testing.29
In a large epidemiological study, normal transit constipation was the most common subtype (59%), followed by pelvic floor dyssyndergia (25%), slow transit constipation (13%), and the mixed type (3%).30
Several treatment modalities have been adopted for constipation such as life-style modification, medications, biofeedback therapy, injection of botulinum toxin,31
sacral nerve stimulation,32
anorectal electrical stimulation,33
and surgical treatment.34
Biofeedback therapy has been studied mainly in patients with pelvic floor dyssynergia. This disorder, which has also been called as anismus, an outlet obstruction or spastic pelvic floor syndrome, is a type of constipation characterized by a failure to relax the puborectalis muscle, the external and internal anal sphincter muscle during the straining for defecation. In recent controlled studies, Chiarioni et al.8,10
reported biofeedback as an effective treatment for pelvic floor dyssynergia superior to laxatives with the improvement to be maintained for a long-term follow interval, while the effect was not found in cases of slow transit constipation. Biofeedback therapy was more effective than conservative treatments or sham feedback treatment in patients with pelvic floor dyssyndergia.13
Altogether these studies suggest biofeedback therapy to be highly effective for pelvic floor dyssynergia with the effects being long-lasting. Furthermore, some studies reported the effectiveness of biofeedback therapy for slow-transit constipation,11,12
which was shown by the improvement of cerebral cortex activity controlling colon motility.35,36
In the present study, we applied biofeedback therapy for refractory constipation patients regardless of the constipation type. The effect of biofeedback therapy was found in 36% of constipation patients with 88.9% of the responder group maintaining the symptom improvements for the long follow-up intervals. The lower outcome of biofeedback therapy just after the completion of biofeedback therapy may have originated from the broad category of participants including those with slow-transit constipation. Furthermore, defecation index, which is specific for pelvic floor dyssynergia,26
was significantly lower in the non-responder group. Again these results could be due to the broad indication of biofeedback therapy with the relatively old participants in our study. Several studies have evaluated the variables associated with successful outcome.8,10,37
Park et al.37
reported the defecation index and pelvic floor dyssynergia as factors influencing the response by multivariate analysis. Other investigators have suggested milder constipation, less frequent abdominal pain, digital facilitation, slow transit, and the defecation index to be associated with successful outcome. But not a common specific variable emerged when a critical review was performed.1
In our study, the rectal sensory parameters showed relatively lower pressures and volumes in the responder group and desire to defecate volume was also significantly lower in the responder group than in the non-responder group. In other words, the non-responder group showed higher minimal volume, desire to defecate volume, urgent volume, and critical volume than the responder group and the difference in desire to defecate volume was statistically significant. Furthermore, similar trend was observed in the follow-up anorectal manometry test after completion of biofeedback therapy. Urgent volume after biofeedback therapy was statistically higher in the non-responder group (180 mL vs. 140 mL, p = 0.031). Rectal hyposensitivity is associated not only with functional GI disorders but also with the response to biofeedback therapy, which is more effective in patients with relatively preserved anorectal physiology. Recently, rectal hyposensitivity has been considered as a causal factor for functional GI disorders and some authors are trying therapeutic modalities such as electrical stimulation.33,38
Chang et al.33
reported the efficacy of electrical stimulation to be comparable to biofeedback therapy in a subgroup of constipation, especially in those with impaired rectal sensation. The pathophysiological mechanisms of rectal hyposensitivity are not well-known, but some studies have shown the association with diminished rectal perception.39
There were no specific physiologic, anatomic, or demographic variable associated with successful outcome.
Fecal incontinence is defined as a recurrent uncontrolled passage of fecal material which presents with a social as well as a personal hygienic problem.40
The cause of fecal incontinence varies and includes abnormalities of intestinal motility, poor rectal compliance, impaired rectal sensation, or weakened pelvic floor muscles.2
In patients with muscle or nerve damage due to disease pathology, obstetric injuries, or rectal prolapse, treatment must be determined based on the cause.2
However, the fact that the pathophysiology and physiological dysfunction to coexist as synergistic factors may make biofeedback therapy a useful first-line therapy. A few studies showed biofeedback therapy to be selectively effective in patients who were initially considered for surgery.41,42
In our study, 11 patients were identified with anal sphincter injury by transanal ultrasound; 6 patients showed thinning of anal sphincter, 5 patient showed defect of anal sphincter. Out of 6 patients showing the thinning, 3 patients responded to biofeedback therapy and among 5 patients showing the defect, only one patient responded to biofeedback therapy. The generally low response rate of biofeedback therapy may lead to surgical modality, but patients who do not have severe damage could be considered as candidates for biofeedback therapy. Demographic features of fecal incontinence are more common in women than men and increase with age in adults, probably due to the pelvic changes and trauma associated with childbirth.43
Women have a better response than men, for reasons not yet determined.44
In our study, female patients (24, 61.5%) were more prevalent than male (15, 38.5%) in the incontinence group, but no statistical difference was noted with regard to the clinical efficacy. Although biofeedback therapy has been reported to be an effective treatment for fecal incontinence for over the past 30 years, the studies performed are lacking in adequately controlled data.1,2
Recent randomized, controlled, and blinded trials have not shown the superiority of biofeedback therapy compared to standard care supplemented by advice and education.22,45
In addition, non-instrumental feedback using simple digital insertion was equally as effective as instrumental biofeedback therapy.23
In spite of these limitations of biofeedback therapy, recent studies have concluded biofeedback-induced improvement to be maintained for a long time interval after treatment.21,22
There continues to be controversy on the use of biofeedback therapy for fecal incontinence, which may account for the reluctance in clinical use and the need for well-designed controlled studies to assess its efficacy. In our study, the clinical effect of biofeedback therapy was observed in 20 patients (51.3%) among 39 participants. Similar to other recent data, all patients who responded to biofeedback therapy have maintained the improvement on the most recent follow-up by telephone interview in the present study. Again the low response rate in the present study may have been due to the broad range of participants including anal sphincter defects caused by surgical procedures. Variables which tend to negatively affect the clinical outcome were reported to be the underlying neurological impairment and the heterogeneity of study group,1
as in our data. No objective factors has been identified in a critical review of many studies to date.1
Some studies have shown the improvement of manometric parameters after biofeedback therapy.23,46
However, most of the data points to inconsistencies between subjective improvement and objective parameters such as manometric changes.47
In our study, a high anal squeezing pressure was an indicator for a good response (p = 0.027). In addition, the responder group showed increases in the anal squeezing pressure after biofeedback therapy (p = 0.019). These results in the incontinence group suggest patients with mild anorectal pathophysiology to present with a good response to biofeedback therapy as in the constipation group. We could not find any other objective parameters than the anal squeezing pressure which correlated with the clinical efficacy evaluated by the anorectal manometry after completion of biofeedback therapy.
In our study, there are several methodological problems. First of all, we did not use the Rome II or Rome III criteria. Instead, biofeedback was performed in patients with either constipation or incontinence who did not respond to conservative medical therapy such as life-style modifications and medications. Second, the criteria for the evaluation of clinical efficacy were rather subjective. Successful outcome was defined depending on the patient's subjective report. Third, follow-up periods were variable. However, as biofeedback therapy has not been established as a standard therapy for constipation or incontinence and the response rate has been known to be inconsistent, it might be a valuable attempt to analyze the efficacy of biofeedback therapy in the crude patient group and share the experience of one institution.
In conclusion, biofeedback therapy in our study showed low successful outcome, but the clinical efficacy was maintained for a long time once the patients responded to the therapy. As patients with mild anorectal pathophysiology show good response to biofeedback therapy, it must be considered as the first therapeutic modality for functional anorectal disorders before they advance into more serious cases.