Anal sphincter incontinence (ASI): results from a functional impairment of ≥1 of the anatomic components that allow normal continence:

•the internal anal sphincter (IAS)

•the external anal sphincter (EAS)

•the pelvic floor muscles (puborectalis)

•the anal cushions that ensure adequate rectal compliance

•the sensory-motor apparatus 

Mechanisms:

•Sphincter defects -perineal tearing, stretching and/or ischemia:

•Obstetrical trauma – OASIS (childbirth trauma, episiotomy)

•Proctologic surgery (keyhole deformity) 

•degeneration of the pelvic floor muscles, which appears with aging and particularly after the menopause as the pelvic floor structures are hormone-sensitive 

Sphincter repair surgery is proposed for large defects of either the EAS, IAS, or both:

•Acute (fresh) anal sphincter and perineal injury -direct reconstruction of the muscle injury by end-to-end sphincter suture. 

-If there is no available surgical specialist, primary repair can be delayed 8–12 h without worse outcomes at 1-year follow-up

-Delayed primary repair is usually not recommended routinely

•Older defects – a secondary sphincter repair (overlaping) also gives good results as long as the LA muscle has a good function

-a delay of at least 6 months to 1 year has been recommended to allow the tissue to recover

Short-term outcomes with anterior sphincteroplasty of the EAS are excellent or good in terms of continence, with a 71% to 86% improvement