Anal endosonography for identifying external sphincter defects confirmed histologically

Abstract

Defects of the external anal sphincter have traditionally been diagnosed by palpation, anal manometry and electromyography (EMG), but anal endosonography enables clear imaging of both the internal and external sphincter muscles. A study was performed to validate the interpretation of ultrasonographic images of external sphincter defects using histology as a ‘gold standard’. In addition the accuracy of clinical examination, manometry, EMG mapping and anal endosonography in the diagnosis of sphincter defects were compared prospectively. Twelve consecutive patients with faecal incontinence (11 women, one man; mean age 46 (range 30–64) years) who required sphincter repair underwent clinical assessment, anal manometry, concentric‐needle EMG mapping and anal endosonography before surgery. The endosonographer was unaware of the history or results of physiological tests and the surgeon performing the repair was blind to the ultrasonographic findings. At operation most or all of the suspected defect was excised and examined histologically. The pathologist was unaware of the endosonographic or operative findings at the time of reporting. Combined operative and histological examination identified an external sphincter defect in nine of the 12 patients. Anal endosonography correctly identified all nine defects and the three normal sphincters. The accuracy of clinical examination was 50 per cent and that of both EMG and anal manometry 75 per cent. In addition, anal endosonography identified a defect of the internal anal sphincter in eight patients. External sphincter defects identified by endosonography have not been previously verified histologically. Precise sphincter assessment is mandatory for the correct management of faecal incontinence. Anal endosonography is more accurate than clinical and conventional physiological methods and also provides information on the internal sphincter.