ANAL ENDOSONOGRAPHY FOR IDENTIFYING EXTERNAL SPHINCTER DEFECTS CONFIRMED HISTOLOGICALLY

Defects of the external anal sphincter have traditionally been diagnos ed by palpation, anal manometry and electromyography (EMG), but anal e ndosonography enables clear imaging of both the internal and external sphincter muscles. A study was performed to validate the interpretatio n of ultrasonographic images of external sphincter defects using histo logy as a 'gold standard'. In addition the accuracy of clinical examin ation, 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 (ran ge 30-64) years) who required sphincter repair underwent clinical asse ssment, anal manometry, concentric-needle EMG mapping and anal endoson ography before surgery. The endosonographer was unaware of the history or results of physiological tests and the surgeon performing the repa ir was blind to the ultrasonographic findings. At operation most or al l 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 examinat ion identified an external sphincter defect in nine of the 12 patients . Anal endosonography correctly identified all nine defects and the th ree 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 sphinct er in eight patients. External sphincter defects identified by endoson ography have not been previously verified histologically. Precise sphi ncter assessment is mandatory for the correct management of faecal inc ontinence. Anal endosonography is more accurate than clinical and conv entional physiological methods and also provides information on the in ternal sphincter.