Confirmation of endosonographic detection of external anal sphincter defects by simultaneous electromyographic mapping.

Anal endosonography was performed in 13 consecutive patients with post-traumatic faecal incontinence. Thirteen acoustic defects in the external anal sphincter (two hyperechoic, four of mixed echogenicity and seven hypoechoic) were analysed electromyographically by locating under ultrasound guidance the tip of a concentric needle within the defect. The electromyographic activity in this zone was compared with ultrasonically normal muscle. Eleven of 13 sonographic defects showed no electrical activity on electromyography, there was one technical electromyography failure, and one defect was too deep to be reached by the electromyography needle. The electromyographic response was normal in each case within ultrasonically normal muscle. Anal endosonography is recommended as the initial investigation to locate defects, which may be confirmed electromyographically thereby limiting the number of painful needle insertions required for complete mapping of the external anal sphincter.