Non-invasive obstetric anal sphincter injury diagnostics using impedance spectroscopy

Obstetric anal sphincter injuries are the most common cause of fecal incontinence in women yet remain under-diagnosed. The aim of this study was to assess the suitability of impedance spectroscopy for diagnosing sphincter injuries arising during delivery. This was a prospective single-center study. 22 female patients were included: 10 with symptoms of sphincter dysfunction, in the early postpartum period, and 12 unaffected, in the distant period of more than 2 years after natural delivery. The presence, extent and severity of anal sphincters injury was assessed by measuring the sphincter parameters in physical examination, the degree of sphincter damage in endoanal ultrasound imaging and the sphincters function parameters in anorectal manometry. All measurements were used as references and compared with the outcomes from the impedance spectroscopy models. Impedance spectroscopy showed the highest precision (with mean accuracy of 83.9%) in relation to transanal ultrasonography. 74.1% of its results corresponded to the results of rectal physical examination and 76.7% - to those of anorectal manometry. The method showed the highest accuracy in the assessment of the sphincter's parameters, both anatomically and functionally. New impedance spectroscopy techniques hold promise for detecting obstetric anal sphincter injuries.