What is the classification and management of obstetric perineal injury?

Classification and Management of Obstetric Perineal Injury

Classification System

Obstetric perineal injuries are classified into four degrees based on the ACOG reVITALize standardized definitions, with proper identification being critical since third- and fourth-degree tears (OASIS) carry a 35-60% risk of long-term anal incontinence. 1

Degree-Based Classification

• First-degree: Injury involving only perineal skin and vaginal mucosa, occurring in 5.5-16.4% of vaginal births 1

• Second-degree: Injury extending to perineal muscles but not involving the anal sphincter, occurring in 29.0-35.1% of vaginal births 1

• Third-degree: Injury involving the anal sphincter complex (external anal sphincter, internal anal sphincter, or both), occurring in 1.8-7.1% of vaginal births 1

• Fourth-degree: Injury extending through the anal sphincter complex into the anorectal mucosa, occurring in 0-0.3% of vaginal births 1

Anatomic Distinctions

• Anterior perineal trauma: Involves the labia, anterior vagina, urethra, or clitoris 2

• Posterior perineal trauma: Involves the posterior vaginal wall, perineal muscles, anal sphincter, and anorectal mucosa 2

Diagnostic Approach

After every vaginal delivery, perform a systematic evaluation including visual inspection, thorough perineal examination, and mandatory digital rectal examination to detect OASIS, as up to 35% of anal sphincter injuries are missed without rectal examination. 2, 1

Essential Examination Components

• Ensure adequate lighting and proper patient positioning before examination 1

• Inform the patient of the need and reasoning for examination 2

• Perform digital rectal examination on all patients to improve OASIS detection rates 1

• If uncertainty exists or the provider is inexperienced, have another trained provider reexamine the tear 2

• The wound can be safely packed and repair delayed 8-12 hours until an experienced provider is available 2

Management by Injury 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. 1

• If suturing is chosen, use continuous non-locking subcuticular technique with absorbable suture material 1

• Pain control with acetaminophen, topical anesthetic sprays or ointments, and local cool packs 2

Second-Degree Tears

For second-degree tears, if hemostatic, use skin adhesive or no suturing for the perineal skin after repairing deeper layers, as this reduces pain, dyspareunia, and improves breastfeeding rates at 3 months. 1

• Repair vaginal epithelium and underlying muscularis with continuous non-locking sutures 1

• Reapproximate perineal muscles in a continuous, non-locking fashion 1

• Use 2-0 or 3-0 delayed absorbable suture material 1

Third- and Fourth-Degree Tears (OASIS)

OASIS repairs require regional or general anesthesia, antibiotic prophylaxis, and use of a surgical checklist to ensure adherence to critical care processes and reduce errors. 1

Preoperative Preparation

• Administer broad-spectrum antibiotic prophylaxis (second or third-generation cephalosporin such as cefoxitin 2g IV) 1

• For penicillin allergy, use gentamicin 5 mg/kg plus clindamycin 900 mg or metronidazole 500 mg 1

• Place Foley catheter given increased risk for urinary retention 2

• Ensure adequate lighting, visualization, and exposure 1

Repair Technique

• Repair sequentially from deep to superficial structures 1

• For the internal anal sphincter (IAS): Use end-to-end technique with either mattress or interrupted sutures using 3-0 delayed absorbable suture, as recommended by the Society of Obstetricians and Gynaecologists of Canada and RCOG 2

• The IAS extends approximately 1.2 cm cephalad from the proximal margin of the external anal sphincter (EAS) and can be identified by grasping torn EAS ends with Allis clamps 2

• For the external anal sphincter: A 2013 Cochrane meta-analysis showed no significant difference in perineal pain or dyspareunia between end-to-end and overlapping techniques, though overlapping repair showed lower fecal urgency and anal incontinence scores at 1 year 2

• Document the laceration type and repair method comprehensively, including technique and suture used 2

Postoperative Care for OASIS

Post-operative care includes stool softeners, pain control, sitz baths, early follow-up, and patient education to achieve optimal outcomes. 1

• Maintain Foley catheter until postoperative day 1, then perform voiding trial to ensure adequate bladder function 2

• Pain control with local cool packs, topical anesthetic sprays or ointments, acetaminophen, and NSAIDs 2

• Avoid opiates if possible given potential complications 2

• Prescribe stool softeners to achieve soft stools and prevent strain 1

• Recommend sitz baths twice daily until first wound check 1

• Arrange early follow-up within two weeks to assess wound healing 1

• Inform patient of the injury and importance of close follow-up 2

Wound Complications and Their Management

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

Risk Factors for 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

Complications Impact on Quality of Life

• Perineal trauma causes persistent perineal pain, dyspareunia, delayed resumption of sexual intercourse, and depression 2

• OASIS is associated with 29-53% flatal incontinence and 5-10% fecal incontinence in the first 6 months postpartum 2

• These complications cause embarrassment, social isolation, and affect quality of life 2

Common Pitfalls to Avoid

• Inadequate examination: Up to 35% of anal sphincter injuries are missed without proper rectal examination 2

• Inadequate lighting: Can cause misclassification of injury severity 1

• Inexperienced repair: If unfamiliar with repair techniques, delay repair 8-12 hours until an experienced provider is available rather than attempting inadequate repair 2

• Failure to use antibiotic prophylaxis: Antibiotics are associated with lower rates of postpartum wound complications 1

• Inadequate pain control: Can interfere with a new mother's ability to care for her newborn 2