A comparison between electromyography and anal endosonography in mapping external anal sphincter defects.

Mapping of the external anal sphincter by anal endosonography was compared with the electromyographic findings in 15 patients with fecal incontinence after perineal trauma. Both examinations showed no defect in three patients. In the 12 patients with muscle defects, there was agreement on the quadrant involved in all patients. In seven patients, there was total agreement in the hours of the defect, in four there was a one hour discrepancy, and in one there was a two-hour difference in the measured defect. Correlation between the two techniques was high (r = 0.96; P less than 0.01). Anal endosonography is better tolerated by patients than electromyographic mapping and is a useful technique for assessing posttraumatic defects of the external anal sphincter.