Guideline No. 457: Obstetrical Anal Sphincter Injuries (OASIS) Part I: Prevention, Recognition, and Immediate Management

Objective

The purpose of this guideline is to promote recognition and preventive strategies for obstetrical anal sphincter injuries. Furthermore, it provides guidance on primary repair and immediate postpartum management for obstetrical anal sphincter tears in order to minimize further negative sequelae.

Target Population

All patients having a vaginal delivery and those who have sustained an obstetrical anal sphincter injury.

Outcomes

Certain preventive strategies have been associated with lower rates of obstetrical anal sphincter injuries (e.g., fetal head flexion and control, appropriate use of mediolateral episiotomy). Management strategies, including appropriate diagnosis and repair of obstetrical anal sphincter injuries, antibiotic prophylaxis, and bowel and bladder function management can decrease associated short- and long-term complications.

Benefits, Harms, and Costs

Implementation of the recommendations in this guideline may increase detection, prevention, and appropriate management of obstetrical anal injuries, thus limiting the future burden associated with these injuries. Implementation of the recommended classification of obstetrical anal sphincter injuries will improve national and international research efforts.

Evidence

Published literature was retrieved through searches of PubMed, Ovid, Medline, Embase, Scopus, and the Cochrane Library from September 1, 2014, through November 30, 2023, using appropriate MeSH terms (delivery, obstetrics, obstetric surgical procedures, obstetric labor complications, anal canal, episiotomy) and keywords (OASIS, obstetrical anal sphincter injury, anal injury, anal sphincter, vaginal delivery, suture, fecal incontinence, anal incontinence, overlap repair, end-to-end repair, bladder protocol, analgesia). Results were restricted to systematic reviews, meta-analyses, randomized controlled trials/controlled clinical trials, observational studies, and clinical practice guidelines. Results were limited to English- or French-language materials. Evidence was supplemented with references from the 2015 Society of Obstetricians and Gynaecologists of Canada guideline no. 330.

Validation Methods

The authors rated the quality of evidence and strength of recommendations using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach. See online Appendix A (Tables A1 for definitions and A2 for interpretations of strong and conditional recommendations).

Intended Audience

Obstetrical care providers.

Tweetable Abstract

Updated Canadian guideline on recognition, prevention and management of obstetrical anal sphincter injuries (OASIS).

SUMMARY STATEMENTS

• 1.
  Obstetrical anal sphincter injuries can lead to significant comorbidities, including anal incontinence, rectovaginal fistula, and pain (moderate).
• 2.
  The strongest risk factors for obstetrical anal sphincter injury include: primiparity, fetal macrosomia, operative vaginal delivery, and midline episiotomy (high).
• 3.
  Complete examination and classification of obstetrical perineal trauma is essential to ensure appropriate repair and improve reporting, thus decreasing the risk of residual anal sphincter defects (moderate).
• 4.
  Although the optimal cutting angle for mediolateral episiotomy has not been clearly established, it appears to be closer to 60° from the midline at crowning (moderate).
• 5.
  Obstetric anal injuries are more commonly associated with forceps-assisted deliveries than with vacuum-assisted deliveries (high).
• 6.
  Suture-related morbidity is similar at 6 weeks following repair with either polyglactin (Vicryl) or polydioxanone (PDS) sutures (moderate).
• 7.
  A rupture of the external anal sphincter can be repaired with either an overlapping or end-to-end technique. Existing evidence does not support recommending one technique over the other. However, the overlapping technique is only feasible with full-thickness external anal sphincter tears (strong).
• 8.
  Obstetrical anal sphincter injuries are associated with an increased risk of postpartum urinary retention (moderate).
• 9.
  Patients with obstetrical anal injuries are at risk for a range of pelvic floor disorders, including anorectal symptoms, urinary incontinence, pelvic organ prolapse, and sexual dysfunction (moderate).

RECOMMENDATIONS

• 1.
  All patients should be carefully examined for perineal and vaginal tears immediately after vaginal delivery. Every patient should be offered a rectal examination for detection of obstetrical anal sphincter injuries and buttonhole tears (strong, moderate).
• 2.
  Clinicians should use Sultan’s classification to grade obstetrical perineal trauma to ensure consistent reporting (strong, moderate).
• 3.
  The degree of perineal laceration should be disclosed to the patient and documented in the medical record (good practice point).
• 4.
  The obstetrical care provider should attempt to slow the delivery of the fetal head at crowning during spontaneous vaginal delivery (via flexion of fetal head, perineal support, and/or cessation of maternal pushing) (strong, moderate).
• 5.
  Given the minimally invasive nature of warm perineal compress and perineal massage, the obstetrical care provider should consider these for prevention of obstetrical anal sphincter injury (strong, moderate).
• 6.
  The obstetrical care provider should follow a policy of restricted episiotomy during spontaneous vaginal delivery, rather than routine use of episiotomy (strong, high).
• 7.
  If episiotomy is indicated, the obstetrical care provider should perform a mediolateral over midline episiotomy (strong, moderate).
• 8.
  In primiparous patients undergoing an operative vaginal delivery, a mediolateral episiotomy should strongly be considered by the obstetrical care provider, especially with forceps-assisted deliveries (strong, high).
• 9.
  Third- and fourth-degree anal sphincter injuries should be repaired by experienced care providers (strong, high).
• 10.
  If a more experienced care provider is required for repair of obstetrical anal sphincter injury, clinicians can delay repair for 8–12 hours with no detrimental effect on anal incontinence (strong, moderate).
• 11.
  A single dose of prophylactic intravenous antibiotics should be administered immediately following repair of obstetrical anal sphincter injury to reduce postpartum wound complications. A second-generation cephalosporin (e.g., cefotetan or cefoxitin) should be administered. For patients with a history of anaphylactic allergy to penicillin, clindamycin can be administered (strong, moderate).
• 12.
  Laxatives should be prescribed following primary repair of obstetrical anal sphincter injury. Constipating bowel agents are not recommended (strong, moderate).
• 13.
  Non-steroidal anti-inflammatory drugs and acetaminophen should be used as first-line analgesics. Opioids should only be used with caution and should be used in conjunction with a laxative to avoid constipation (strong, moderate).
• 14.
  Health care providers should pay careful attention to voiding function in patients with an obstetrical anal sphincter injury, particularly as these patients may have a number of compounding risk factors (strong, moderate).
• 15.
  Clinicians may consider bladder rest via indwelling catheter for up to 24 hours following repair of obstetrical anal sphincter injury, particularly in patients with numerous risk factors for postpartum voiding dysfunction (good practice point).