[Diagnosis of anterior perineal anus (APA)--significance of electromyographic evaluation of the external anal sphincter location].

APA is a common cause of constipation, and is the mild case of the imperforated anus. On diagnosing APA, anterior displacement of the anus and normal distribution of the external anal sphincter to the anus are essential. To determine the location of the anus in the perineum simple clinical technique was developed. In 61 normal cases, the result of measurement was almost same in each sex, but in 3 APA cases the location were anteriorly dislocated than normal cases. Distribution of the external anal sphincter was evaluated with electromyographic technique, and location map of the sphincter was made. In 3 APA cases, the anus was totally surrounded by the external anal sphincter, but in 17 ano-cutaneous fistula cases, the opening was anteriorly dislocated to the sphincter distribution map. As a conclusion, newly proposed simple clinical technique to determine anal location and electromyographic examination of the external and sphincter distribution are very useful in objective diagnosis of APA.