Third- and Fourth-degree Perineal Tears, Management
Classification (Sultan classification, adopted by RCOG and the International Consultation on Incontinence)
Obstetric anal sphincter injuries (OASIS) encompass third- and fourth-degree tears.
- First-degree tear: injury to perineal skin and/or vaginal mucosa only.
- Second-degree tear: injury to the perineum involving perineal muscles but not the anal sphincter.
- Third-degree tear: injury to the perineum involving the anal sphincter complex.
- Grade 3a: less than 50% of external anal sphincter (EAS) thickness torn.
- Grade 3b: more than 50% of EAS thickness torn.
- Grade 3c: both EAS and internal anal sphincter (IAS) torn.
- Fourth-degree tear: injury to the perineum involving the anal sphincter complex (EAS and IAS) and the anorectal mucosa.
- If there is doubt about the degree of a third-degree tear, classify to the higher degree rather than the lower.
- A rectal buttonhole tear — mucosal injury with an intact sphincter complex — is, by definition, not a fourth-degree tear, but must be documented and repaired separately as it can lead to a rectovaginal fistula if missed.
Risk Factors
Risk factors are recognised but do not allow accurate prediction of OASIS on an individual basis. Identified factors include: Asian ethnicity, nulliparity, birthweight >4 kg, shoulder dystocia, occipito-posterior position, prolonged second stage of labour (risk rises with duration), and instrumental delivery — particularly forceps without episiotomy, which carries the highest reported odds ratio of the listed factors. Ventouse with a mediolateral episiotomy is associated with a lower risk than ventouse without one. Recurrence risk of OASIS in a subsequent pregnancy is significantly increased (risk factors for recurrence include Asian ethnicity, forceps delivery, and birthweight >4 kg).
Prevention
- Evidence for a protective effect of routine episiotomy is conflicting; a mediolateral episiotomy should be considered for instrumental deliveries.
- Where performed, the mediolateral technique is recommended, cut at an angle of 60 degrees away from the midline when the perineum is distended (NICE recommends 45–60 degrees).
- Manual perineal protection ("hands on") at crowning can be protective.
- Warm compresses applied to the perineum during the second stage of labour reduce the risk of OASIS (Grade A evidence, from Cochrane review).
Identification
All women having a vaginal delivery are at risk of OASIS or an isolated rectal buttonhole tear and should be examined systematically after birth, including a digital rectal examination, to assess the extent of damage before suturing. Endoanal ultrasound is not recommended for routine immediate postpartum detection — current evidence treats it as a research tool at that stage due to limitations in availability, image quality, and interpretation.
Repair
- Repair of third- and fourth-degree tears should be conducted by an appropriately trained clinician, or a trainee under supervision.
- Repair should take place in an operating theatre, under regional or general anaesthesia, with good lighting and appropriate instruments and an assistant. Repair in the delivery room may occur in certain circumstances only after discussion with a senior obstetrician.
- Figure-of-eight sutures should be avoided (haemostatic, may cause tissue ischaemia).
- A rectal examination should be performed after repair to check no suture has inadvertently passed through the anorectal mucosa; if found, it should be removed.
- Anorectal mucosa: repaired with continuous or interrupted sutures, using 3-0 polyglactin (preferred over PDS, which may cause more irritation/discomfort in the anal canal).
- Internal anal sphincter (IAS): where identifiable, repaired separately with interrupted or mattress sutures — not overlapped.
- External anal sphincter (EAS): for full-thickness tears, either the overlap or end-to-end technique may be used with equivalent outcomes (Grade A). For partial-thickness tears (all 3a and some 3b), an end-to-end technique should be used, since overlap requires two free muscle ends and would place partial tears under undue tension.
- For EAS/IAS muscle repair, either monofilament (e.g. 3-0 PDS) or modern braided sutures (e.g. 2-0 polyglactin) may be used with equivalent outcomes.
- Surgical knots should be buried beneath the superficial perineal muscles to reduce the risk of knot/suture migration to the skin.
Postoperative Management
- Broad-spectrum antibiotics are recommended following OASIS repair to reduce the risk of postoperative infection and wound dehiscence (Grade B; based on limited trial evidence).
- Laxatives are recommended postoperatively to reduce the risk of wound dehiscence, since passage of a hard stool can disrupt the repair; a stool softener such as lactulose is typically used for around 10 days.
- Bulking agents should not be given routinely alongside laxatives — a trial of lactulose plus ispaghula husk showed more frequent postpartum incontinence than lactulose alone.
- Physiotherapy following repair may be beneficial and should be advised.
- Local protocols should govern antibiotic, laxative, examination, and follow-up practice, given variation between units.
Follow-up and Future Deliveries
- Women should be reviewed at a convenient time, usually 6–12 weeks postpartum, ideally by a clinician with a special interest in OASIS; where resources allow, follow-up should be in a dedicated perineal clinic with access to endoanal ultrasonography and anal manometry.
- Women with incontinence or pain at follow-up should be considered for referral to a specialist gynaecologist or colorectal surgeon.
- Prognosis: 60–80% of women are asymptomatic at 12 months following delivery and EAS repair.
- For future pregnancies, all women with a prior OASIS should be counselled on mode of delivery, with this documented in the notes. Prophylactic episiotomy in a subsequent delivery is not evidence-supported and should only be performed if clinically indicated. Women who are symptomatic, or who have abnormal endoanal ultrasonography and/or manometry, should be counselled about the option of elective caesarean birth. The risk of sustaining a further third- or fourth-degree tear in a subsequent delivery is reported at 5–7%.
High-Yield Exam Points
- Know the full classification cold, especially the 3a/3b/3c subdivision (<50% EAS, >50% EAS, EAS+IAS) versus fourth-degree (EAS+IAS+anorectal mucosa) — this is the single most testable fact from this guideline.
- Repair setting: theatre, regional/general anaesthesia, good lighting — not a ward-based procedure except in specific circumstances agreed with a senior obstetrician.
- Suture choice: 3-0 polyglactin for anorectal mucosa; EAS/IAS repaired with monofilament (3-0 PDS) or braided (2-0 polyglactin) with equivalent outcomes; figure-of-eight sutures are avoided throughout.
- EAS repair technique: overlap or end-to-end for full-thickness tears (equivalent outcomes); end-to-end only for partial-thickness (3a/some 3b) tears.
- Postoperative bundle: broad-spectrum antibiotics + laxative (not bulking agents in combination) + follow-up at 6–12 weeks.
- Highest-risk instrumental delivery factor: forceps without episiotomy.
Source: RCOG Green-top Guideline No. 29 (3rd edition) (June 2015 (previously published July 2001, March 2007); review process was due to commence in 2018 — a 4th edition has not yet been identified as published, so treat later figures with caution)
Read the original on rcog.org.uk
MRCOG AI is an independent educational tool. It is not affiliated with, endorsed by, or connected to the Royal College of Obstetricians and Gynaecologists (RCOG).