Perineal Wound Dehiscence

Perineal wound dehiscence is breakdown of the repair of any perineal tear or cut, including second, third and fourth degree tears and episiotomy, with gaping of the skin, muscle or sphincter repair. It is most often caused by infection, haematoma and tension, and is more common after third and fourth degree tears. It matters because deep dehiscence involves the anal sphincter and can lead to faecal incontinence and rectovaginal fistula.

• Risk factors: infection, haematoma, diabetes, obesity, anaemia, malnutrition, smoking, third or fourth degree tear, instrumental delivery, constipation and straining.
• Usually appears on days 4 to 14.
• Sphincter involvement needs specialist repair.

Women have increased perineal pain, gaping of the wound with visible tissue, discharge, sometimes fever, and in deep breakdown leaking of stool or flatus through the vagina. The wound may be infected or clean.

• Gaping wound with granulation or slough.
• Loss of anal sphincter tone in deep breakdown.
• Differential diagnosis: infection, haematoma, retained swab, rectovaginal fistula, sphincter disruption, necrotising fasciitis, wound dehiscence from tension alone.
• Complications: infection, abscess, rectovaginal fistula, faecal incontinence, scarring, dyspareunia, chronic pain, repeat surgery.

The approach is detailed examination for depth, sphincter integrity and infection.

• Inspect with good light and analgesia; measure the gap; digital rectal examination for sphincter tone and rectal mucosa defects; look for stool in the vagina.
• Temperature, pulse; wound swab for culture; full blood count, C-reactive protein, glucose.
• Endo-anal ultrasound or MRI where available for a sphincter defect; ultrasound for collection.
• Haemoglobin and nutrition status.

The principle is to treat infection, wait for a clean granulating wound, and repair early or late depending on depth and sphincter injury.

• Supportive: irrigate with sodium chloride 0.9 percent twice daily; sitz baths 3 times daily; keep dry; remove loose sutures; high fibre diet and fluids; protein rich diet; glucose control; stop smoking; breastfeeding continues.
• Pharmacological: amoxicillin-clavulanate 625 mg oral 8-hourly for 7 days when infected; ceftriaxone 2 g IV once daily plus metronidazole 500 mg IV 8-hourly for severe infection; lactulose 15 mL oral 12-hourly; ispaghula husk 3.5 g oral 12-hourly with water for stool bulk; paracetamol 1 g oral 6-hourly (maximum 4 g in 24 hours); ferrous sulphate 200 mg oral 8-hourly for 3 months if anaemic.
• Procedures: debridement of dead tissue; early secondary repair after 6 to 14 days under anaesthesia when clean (superficial or muscle breakdown); delayed repair at 3 months for sphincter involvement, rectovaginal fistula or a large defect, with sphincteroplasty by a trained surgeon; temporary defunctioning stoma for complex fistula.
• Special groups: women with sphincter involvement are counselled on elective caesarean section in a later birth if symptoms or abnormal anal tests persist; diabetic women need insulin to keep glucose below 10 mmol/L.
• Red flags: stool or flatus from the vagina, fever above 38 degrees Celsius, spreading redness, severe pain, foul pus, dusky skin.
• Follow-up: wound review every 3 to 4 days until healed; review at 1 week, 2 weeks and 6 weeks; anal manometry or ultrasound at 3 months if incontinence persists.