What is the definition, grading, and management of perineal tears in women, particularly those who have experienced a vaginal delivery?

Perineal Tears: Comprehensive Overview

Definition

Perineal trauma after vaginal delivery occurs either spontaneously or iatrogenically through episiotomy, involving structures from the pubic arch to the coccyx. 1 The perineum is divided into anterior (urogenital) and posterior (anal) triangles. 1

• Anterior perineal trauma involves the labia, anterior vagina, urethra, or clitoris 1
• Posterior perineal trauma involves the posterior vaginal wall, perineal muscles, anal sphincter (external, internal, or both), and anorectal mucosa 1

Classification System

The American College of Obstetricians and Gynecologists (ACOG) standardized perineal tear classification through the 2012 reVITALize Obstetrics Data Definitions Conference: 1

First-Degree Tears

• Involve only skin or mucosa without affecting underlying muscle tissue 2
• Limited to superficial epithelial layer 2

Second-Degree Tears

• Involve perineal skin, vaginal epithelium, and perineal muscles 1
• Do not extend to the anal sphincter complex 2

Third-Degree Tears (OASIS)

• Extend into or through the external anal sphincter 3
• Subdivided based on extent of sphincter involvement 4

Fourth-Degree Tears (OASIS)

• Extend through the anal sphincter complex and involve the anorectal mucosa 1
• Most severe form of perineal trauma 3

Prevalence

Perineal trauma affects approximately 90% of women after vaginal birth, with second-degree tears occurring in 40% of primiparous women. 5

• First-degree tears: 5.5% to 16.4% 1
• Second-degree tears: 29.0% to 35.1% 1
• Third-degree tears: 1.8% to 7.1% (approximately 3.3% overall) 1
• Fourth-degree tears: 0% to 0.3% (approximately 1.1% overall) 1
• Up to 35% of anal sphincter injuries are missed without proper examination 1

Diagnosis and Examination

After all vaginal deliveries, perform systematic evaluation including visual inspection, thorough perineal examination, and mandatory digital rectal examination, as this improves OASIS detection rates. 1, 2

Essential Examination Steps:

• Ensure adequate lighting before examination 1, 2
• Inform the patient of the need and reasoning for examination 1
• Perform visual inspection of all perineal structures 1
• Conduct thorough perineal palpation 4
• Perform digital rectal examination on all patients - this is critical as rectal exam improves detection of OASIS and up to 35% of sphincter injuries are missed without it 1, 2
• If uncertainty exists regarding OASIS diagnosis, obtain a second experienced examiner 1
• Routine imaging is not needed immediately after delivery, as clinical examination by a knowledgeable birth attendant has equivalent OASIS detection rates to endoanal ultrasound 1

Common Diagnostic Pitfalls:

• Inadequate lighting causes misclassification of injury severity 2
• Failure to perform rectal examination leads to missed anal sphincter injuries 6
• Relying solely on visual inspection without digital examination 6

Management by Degree

First-Degree Tears

For hemostatic first-degree tears, use skin adhesive or no suturing rather than traditional suturing, as this reduces pain and procedure time with equivalent functional outcomes. 2

• Skin adhesive is associated with shorter procedure time (2.29 vs 7.88 minutes), less pain, and greater satisfaction 1
• Time to become pain-free is significantly shorter with skin adhesive (3.18 vs 8.65 days) 1
• Three management options exist: no suturing, skin adhesive, or surgical suturing 1

Second-Degree Tears

For second-degree tears, repair deeper perineal muscle layers first, then use skin adhesive or no suturing for hemostatic perineal skin, as this reduces pain, dyspareunia, and improves breastfeeding rates at 3 months. 2

• Continuous non-locking subcuticular sutures are preferred over interrupted transcutaneous sutures, as this avoids nerve ending damage and reduces pain 6

Third- and Fourth-Degree Tears (OASIS)

For OASIS, repair sequentially from deep to superficial structures using regional or general anesthesia, with end-to-end technique using 3-0 delayed absorbable suture for the internal anal sphincter. 2

Pre-Repair Preparation:

• Ensure adequate lighting and patient analgesia 1
• Consider regional or general anesthesia for OASIS repair 1, 6
• Prepare laceration site with betadine or chlorhexidine 1
• Administer prophylactic antibiotics: first-generation or second-generation cephalosporin; for penicillin allergy use gentamicin plus clindamycin or metronidazole 6
• Place Foley catheter before initiating repair 6
• The surgical team must include a specialist physician with appropriate expertise (preferably obstetrician, gynecologist, or coloproctology specialist) 4

Repair Technique:

• Repair sequentially: rectovaginal fascia, perineal body muscles, then skin 6
• For internal anal sphincter: use end-to-end technique with mattress or interrupted sutures using 3-0 delayed absorbable suture 2
• For external anal sphincter: use either end-to-end or overlapping technique based on surgeon familiarity, as neither offers superior results 4
• Count all surgical instruments, sponges, and sutures pre- and postoperatively 6

Postoperative Management

For OASIS Repairs:

Prescribe stool softeners for at least 6 weeks to achieve soft stools and prevent strain, maintain Foley catheter until postoperative day 1, then perform voiding trial. 6, 2

• Recommend sitz baths twice daily for comfort and tissue healing 6
• Provide pain control with acetaminophen and ibuprofen as primary analgesics; reserve opiates only if needed 6
• Apply ice packs for additional pain relief 6
• Arrange follow-up within two weeks, ideally in a specialized postpartum perineal clinic 6
• Daily cleaning under running water is recommended, particularly after bowel movements 4
• Inform patients about impact on subsequent births and possibility of anal incontinence 4

For All Repairs:

• Antibiotic administration is associated with decreased wound infection and reduced dehiscence rates 6

Complications and Long-Term Outcomes

The baseline risk of wound complications after OASIS repair is high, with infection rates of 19.8% and dehiscence rates of 24.6%, leading to worsened physical, emotional, and sexual satisfaction persisting up to 9 months postpartum. 2

Functional Complications:

• OASIS is associated with 29-53% flatal incontinence and 5-10% fecal incontinence in the first 6 months postpartum 2
• Severe perineal lacerations increase risk of pelvic floor injury, fecal and urinary incontinence, pain, and sexual dysfunction 3
• Symptoms may persist or be present many years after giving birth 3
• Approximately 10% of women develop anal incontinence symptoms within a year following vaginal birth with OASIS 5

Wound Complications:

• Overall infection rates after perineal trauma range from 0.1% to 23.6% 2
• Overall dehiscence rates range from 0.21% to 24.6% 2
• Risk increases with missed diagnosis, inappropriate repair technique, and lack of surgeon experience 2

Management of Wound Dehiscence

If dehiscence occurs, perform thorough visual inspection and mandatory digital rectal examination to assess extent, presence of infection, and anal sphincter involvement. 6

Conservative Management:

• Prescribe stool softeners for six weeks 6
• Recommend sitz baths twice daily 6
• Provide pain control with acetaminophen and ibuprofen; reserve opiates only if needed 6
• Apply ice packs 6
• Arrange follow-up within two weeks in specialized postpartum perineal clinic 6

Surgical Management for Infected Dehiscence:

• Administer second- or third-generation cephalosporin, or metronidazole with gentamicin (or clindamycin for penicillin allergy) 6
• If concern exists for anal sphincter compromise, perform endoanal ultrasound 6
• Refer to specialized postpartum perineal clinic for expert evaluation 6

Economic and Medicolegal Impact

OASIS has significant medicolegal implications, with economic burden ranging from £3.7 to £9.8 million in the UK (2013-2014) and approximately $83 million in the US (2007-2011). 5