Occult obstetric trauma and anal incontinence.

Obstetric trauma is by far the commonest cause of anal incontinence in women. Denervation and reinnervation of the pelvic floor and anal sphincter following vaginal delivery has been previously demonstrated. The advent of anal endosonography, however, has enabled the identification of occult anal sphincter defects following vaginal delivery. It is now possible to identify risk factors and change obstetric practice accordingly so as to minimize anorectal morbidity.