Repair of perineal tear
Classification of perineal tear
The severity of perineal tear is classified according to the depth of the perineal tissues involved as well as whether the anal sphincters are damaged, as shown in Table 33.2 (15).
Complications of perineal tear include severe postpartum haemorrhage, wound breakdown and infection, anovaginal fistula, anal incontinence, and dyspareunia. Repair of first- and second-degree tears is similar to episiotomy repair, but repair of third- and fourthdegree tears, which are also called obstetric anal sphincter injuries (OASIS), require special precaution and skill.
Table 33.2 Definition of different degrees of perineal tears according to the severity
| Classification | Definition |
| First degree | Injury to perineal skin and/or vaginal mucosa |
| Second degree | Injury to perineum involving perineal muscles but not involving the anal sphincter |
| Third degree | Injury to the perineum involving the anal sphincter complex: |
| Grade 3a | Less than 50% of external anal sphincter torn |
| Grade 3b | More than 50% of external anal sphincter torn |
| Grade 3c | Both external anal sphincter and internal anal sphincter are torn |
| Fourth degree | Injury to perineum involving the anal sphincter complex and anorectal mucosa |
Repair of third- and fourth-degree perineal tear (OASIS)
Prior to repair of an episiotomy and/or perineal tear, all women should have a systematic examination of the perineum, including a digital rectal examination, to assess the extent and severity of the tear.
Failure to identify a major perineal tear (third- or fourth-degree tears) would result in inadequate repair leading to the risk of anal incontinence and other wound complications. Adequate exposure and complete relaxation of the woman are essential for repair of major perineal tears. Hence the procedure should be performed in the operating theatre with good lighting and under either spinal or general anaesthesia.The anorectal mucosa, internal anal sphincter, and external anal sphincter should be repaired separately to improve the likelihood of subsequent anal continence (16). The anorectal mucosa should be repaired with continuous or interrupted polyglactin sutures, which causes less irritation and discomfort than polydioxanone (PDS) sutures. The internal anal sphincter is to be repaired with interrupted or mattress sutures using either polyglactin or PDS sutures. A third- degree tear where the whole external anal sphincter is torn can be repaired by an overlapping or end-to-end technique using either polyglactin or PDS sutures, whereas if the external anal sphincter is only partially torn, the end-to-end technique is preferred (17). In all three layers of repair, figure-of-eight sutures should be avoided because they may cause tissue ischaemia (18).
Postoperatively, women should be given broad-spectrum antibiotics to reduce the risk of wound infection and dehiscence. Laxatives such as lactulose are prescribed to soften the stool which may allow better healing of the wound. Women should be advised to practise pelvic floor exercises in the postnatal period.
Follow-up after repair
Women should be followed up in 2-3 months after the repair to assess wound healing and to look for complications, especially anal incontinence. About 60-80% of women will become asymptomatic by 12 months after repair. Women who have persistent symptoms should be assessed carefully and endoanal ultrasonography and/or manometry may be necessary to assess for anal sphincter defects. The option of elective caesarean delivery should be discussed in future pregnancies.