From: Management of obstetric anal sphincter injury: a systematic review & national practice survey
Injury | Definition |
---|---|
Second Degree | Injury to the perineum involving perineal muscles but not involving the anal sphincter |
Third Degree | Injury to the perineum involving the anal sphincter complex (EAS and IAS) |
 | 3a : Less than 50% of EAS thickness torn |
 | 3b : More than 50% of EAS thickness torn |
 | 3c : IAS torn |
Fourth Degree | Injury to the perineum involving the anal sphincter complex (EAS and IAS) and rectal mucosa. |