External anal sphincter atrophy on endoanal magnetic resonance imaging adversely affects continence after sphincteroplasty

Background: There is still considerable debate about the value of preoperat ive anorectal physiological parameters in predicting the clinical outcome a fter sphincteroplasty. Recently it has been reported that atrophy of the ex ternal anal sphincter can be clearly shown with endoanal magnetic resonance imaging (MRI). The aims of this study were to investigate the prevalence o f external anal sphincter atrophy in women with anterior sphincter defects due to obstetric injury and to determine the impact of external anal sphinc ter atrophy on the outcome of sphincteroplasty. Methods: In this prospective study, 20 consecutive women (median age 50 (ra nge 28-75)years) with faecal incontinence due to obstetric trauma were asse ssed before operation with endoanal ultrasonography and endoanal MRI. The e xternal anal sphincter was examined and evaluated for the presence of atrop hy. The clinical outcome of sphincteroplasty was interpreted without knowle dge of the magnetic resonance and ultrasonogaphic images. Results: In all patients anterior sphincter defects could be demonstrated w ith ultrasonography and MRI. External anal sphincter atrophy could only be demonstrated on MRI. Eight of 20 patients had external anal sphincter atrop hy. Continence was restored in 13 patients. Outcome was significantly bette r in those without external anal sphincter atrophy (11 of 12 patients versu s two of eight; P = 0.004). Conclusion: External anal sphincter atrophy can only be visualized on endoa nal MRI and affects continence after sphincteroplasty. Endoanal MRI is valu able in the preoperative assessment of patients with faecal incontinence.