Endosonographic evaluation of patients with anal incontinence: findings and influence on surgical management.

Abstract

Endosonography using an anal probe gives detailed information about the internal and external anal sphincters. The goals of this study were to evaluate findings at anal endosonography in patients with anal incontinence and to study whether endosonography might replace needle electromyographic mapping in providing information on the external anal sphincter. Furthermore, we compared the type of sphincter damage found by endosonography with the anal canal pressures and studied the value of endosonography for selecting the most effective surgical treatment. Forty-eight patients with incontinence for either gas (17 patients) or feces (31 patients) were studied. Nineteen patients had idiopathic incontinence, 29 were incontinent as a result of previous obstetrical or surgical trauma. Endosonography and measurement of anal canal pressures were performed in all patients; 40 had needle electromyography. The endosonograms were evaluated without knowledge of the clinical findings, and the endosonographic findings were correlated with the results of needle electromyography, with the anal pressures, and with the type of surgery subsequently performed. In 30 patients, surgery was subsequently planned on the basis of the results of endosonography and the anophysiologic examinations. Endosonograms showed defects of the external sphincters in 27 patients, 12 of whom had internal sphincter defects also. One patient had an abnormal thinning of the external sphincter. Eight patients had defects of the internal sphincter as the only finding. Twenty-two of the patients with sonographically detected defects or thinning of the external sphincter had electromyography, which showed defects of the external sphincter in 18; four defects in the middle and upper anal canal were not found. The sphincteric defects found by endosonography did not correlate with the anal canal pressures. Sphincter reconstruction was offered to most patients who had damage to the external sphincter; patients with isolated defects in the internal sphincter or intact internal and external sphincters were offered a number of other surgical procedures. Endosonography can be used in place of the invasive electromyographic mapping for detecting defects of the external sphincter, and endosonography also gives additional information on the internal sphincter, which cannot be obtained by other means. No correlation between the anal pressures and the type of sphincter damage found by endosonography can be demonstrated. The main reason for performing endosonography is to detect defects in the external sphincter, for which surgical reconstruction is most likely to be done, whereas visualization of internal sphincter defects seems to have no influence on surgical management and does not lead to any specific treatment.