The "uninhibited rectum": a cause of fecal incontinence

The uninhibited (unstable) rectum has been defined as a cause offecal incontinence (FI) in patients with supraconal lesions. In this study, we tested the hypothesis that the uninhibited rectum may be a cause of FI in patients with normal anal pressure and sphincteric mechanism who were considered to have idiopathic FI.

The study comprised 82 patients (mean age 38.2 +/- 11.2 years; 58 women and 24 men) with idiopathic FI and a control group of 20 healthy volunteers (mean age 36.3 +/- 10.6 years; 14 women and 6 men). Inclusion criteria for FI patients were normal electromyogram of the external anal sphincter and puborectalis muscle, and normal anal sensation, pressure, and endosonography. Rectometry was performed using rectal balloon inflation with CO2 at a rate of 150 cc/min. Rectometrograms were assessed quantitatively and qualitatively.

In 79 FI patients, the first rectal sensation was not felt. Urge was perceived at the time of balloon expulsion, which could not be prevented by voluntary sphincteric squeeze. In the remaining 3 patients, the first sensation was perceived but urge coincided with balloon expulsion. Rectometrography showed moderate and gross fluctuations in the tone limb that were not associated with significant changes in intra-abdominal pressure. This contrasted with normal subjects in whom the tone limb exhibited no fluctuations or minor fluctuations that roughly paralleled the intra-abdominal pressure fluctuations. The rectal distension volume at balloon expulsion was significantly lower in FI patients than in controls (P < .05).

These findings suggest that FI can be explained by the fact that the first rectal sensation was that of urge, which was perceived synchronously with balloon expulsion. That is, the balloon had been expelled before the patient could voluntarily squeeze the sphincters to abort expulsion. We postulated that during inflation with small volumes, the rectum did not adapt as in controls, but responded with contractions, which appear to be reflected in the multiple fluctuations in the tone limb. FI in these patients appears to be a consequence of the unstable or uninhibited rectum.