Endoluminal ultrasound is preferable to electromyography in mapping anal sphincteric defects

Assessment of complex sphincteric defects in patients with fecal incontinence by digital rectal examination and intraoperative dissection can be difficult in the presence of excessive scarring. Adjunctive investigation such as endoluminal ultrasound (ELUS) and needle electromyography (EMG) may provide objective evidence of the nature and extent of the sphincteric defects. In a series of 11 patients, ELUS of the anal canal with a 10-MHz transducer (focal zone of 1-4 cm) accurately detected defects in the external anal sphincter (EAS) in seven of seven patients, defects in the internal anal sphincter (IAS) in eight of eight patients, and integrity of both sphincters in two patients. These findings were confirmed by needle EMG of the EAS alone in five patients, by operative findings at a perineal sphincteroplasty operation in six patients, and by both in two patients. ELUS was associated with less pain than was needle EMG (pain score 4 vs. 10, 10 being most painful) and provided high-resolution radial images of both the EAS and the IAS. Thus, ELUS seems preferable to EMG in mapping anal sphincteric defects and can be a useful anatomic adjunct to physiologic studies of anorectal function in patients with fecal incontinence.