Obstetric Anal Sphincter Injuries - A Complication of Vaginal Delivery

What Are Obstetric Anal Sphincter Injuries?

Obstetric anal sphincter injuries (OASIS), also known as third and fourth-degree perineal lacerations, are complications occurred during vaginal delivery. The tears or lacerations extend from the perineum to the anus (or rectum) and include the muscles responsible for opening and closing the anus. It can often lead to morbidities like wound breakdown or perineal pain, loss of bowel control, and sexual dysfunction in women.

What Are the Primary Risk Factors for Obstetric Anal Sphincter Injuries?

The risk factors for obstetric anal sphincter injuries are as follows-

• First vaginal delivery.

• Heavy baby.

• Fetal distress or post-delivery.

• A persistent occipito-posterior position during delivery.

• Prolonged labor.

• Shoulder dystocia (when one or both shoulders of the baby get stuck during vaginal delivery).

• Midline episiotomy (incision made from the middle of the vaginal toward the anus).

• An instrumental vaginal delivery.

• Mother has weak tissue or short perineum.

• Infibulation.

• Maternal diabetes.

• Waterbirth.

What Are the Symptoms of Obstetric Anal Sphincter Injuries?

Obstetric anal sphincter injuries can significantly impact women by impairing their quality of life. The following symptoms can be noticed after an OASIS injury:

• Perineal pain.

• Edema and bruising due to tight sutures, infection, or wound breakdown.

• Urinary retention and defecation problems in the postpartum period.

• Dyspareunia (genital pain before, during, or after sexual intercourse).

• Altered sexual function.

• In severe cases, there is abscess formation, wound breakdown, and rectovaginal fistula formation.

• Anal incontinence and anorectal symptoms.

How Are Obstetric Anal Sphincter Injuries Classified?

Perineal tears that occur commonly during vaginal birth are graded based on severity:

1. Grade 1 - Injury to perineal skin only.

2. Grade 2 - Injury to the perineum involving perineal muscles (not the anal sphincter).

3. Grade 3 - Through external anal sphincter muscle.

• 3a - Less than 50 % of external anal sphincter thickness torn.

• 3b - More than 50 % of the external anal sphincter thickness is torn.

• 3c - Both external and internal anal sphincter torn.

4. Grade 4 - Injury to the perineum involving the anal sphincter complex and anal epithelium.

First-grade and second-grade injuries usually do not require intense reparative surgery. Instead, doctors can simply suture the area on the delivery table. As a result, the healing and postoperative outcomes are primarily good.

The third-grade and fourth-grade perineal tears are obstetric anal sphincter injuries. They are more severe injuries and require reparative surgery.

How to Prevent Obstetric Anal Sphincter Injuries?

During delivery, sometimes it becomes impossible to avoid obstetric anal sphincter injuries due to the circumstances, but the following measures can be taken to prevent obstetric anal sphincter injuries-

• Head Control - Slowing down the delivery of the head and using only the uterine expulsive efforts.

• Perineal Support - Apply warm compresses to the perineum and use intrapartum perineal massage.

• Delivery position.

• Episiotomy - Restricted use of episiotomy is preferable in women having a spontaneous vaginal delivery.

• Other Factors - Antepartum perineal massage, pushing position, open versus closed glottis pushing, Ritgen’s maneuver, water birth, and delayed pushing (in women with epidural) do not show any protective effect on the anal canal.

• Commencing perineal massage from 35 weeks of the pregnancy.

How Is Obstetric Anal Sphincter Injury Repaired?

• Obstetric anal sphincter injury repairs are carried out in the delivery room or the operating room.

• It can be commonly repaired under local anesthetic or general or regional anesthesia.

• Sutures - After analyzing the severity, location, and depth of injury, stitches are placed by the doctors to repair the tear. Sutures can be absorbable as well as non-absorbable.

• Repair of the Anal Mucosa - The mucosal repair can be carried out with an interrupted vicryl suture or continuous submucosal suture.

• Repair of the External and Internal Anal Sphincters - Suturing is done by either end-to-end repair or overlap repair techniques. The procedure is also known as sphincteroplasty (sphincter repair).

• Women with anal incontinence following OASIS should be referred for pelvic floor physiotherapy.

How to Care after Obstetric Anal Sphincter Injury?

Following an obstetric anal sphincter injury (OASIS), the following medical attention is likely to be provided:

• Pain Relief - Ibuprofen or Paracetamol may be administered to the patient as a form of pain relief.

• Antibiotics - To lower the risk of infection, one might be prescribed antibiotics.

• Laxatives - To help an individual loosen up, the doctor may prescribe laxatives.

• Physiotherapy - One can be offered physiotherapy during the hospital stay or a follow-up appointment.

• Follow-up - A clinician with a special interest in OASIS may review the patient six to 12 weeks after delivery.

• Referral - If incontinence or pain develops during the follow-up, one may be referred to a specialized gynecologist or colorectal surgeon.

Other factors to think about are:

• Steer clear of bulking and constipating agents.

• Mediolateral episiotomy as opposed to midline episiotomy.

• Discuss the extent of the injury with the patient.

• Realizing that nerve damage typically affects the left side more than the right and is not always symmetrical.

• Understanding that PTSD, or post-traumatic stress disorder, can arise as soon as the occurrence or weeks, months, or years later as a result of birth trauma

What Happens After the Repair of an Obstetric Anal Sphincter Injury?

• Follow-Up - Following delivery, one ought to schedule a follow-up appointment six to 12 weeks later. During this visit, one may discuss symptoms they might not normally bring up, like fecal incontinence or flatus.

• Prophylactic Antibiotics - The doctor will prescribe antibiotics to prevent infections and complications from postpartum perineal wounds after the procedure. Second-generation Cephalosporins are usually prescribed.

• Postoperative Bowel Regimen - It varies from patient to patient. It consists of laxatives and bulking agents to avoid constipation and any damage to the repaired tissues from the passage of hard stool. The bowel motions in the immediate postoperative period may threaten the integrity of the repair, so bowel confinement techniques are used.

• Postoperative Analgesia - It is used to relieve perineal pain due to trauma. As opioids have a constipating effect, NSAIDs (nonsteroidal anti-inflammatory drugs) in conjunction with Acetaminophen are preferred.

• Bladder Catheterization - A process where a flexible tube is inserted into the bladder to empty urine.

• Physiotherapy - During the hospital stay or at a follow-up visit, patients may be offered physiotherapy.

• Pelvic Rest - To give the incision six weeks to heal, the patient may be advised to completely rest the pelvic muscles.

• Wound Assessment - One to two weeks following discharge, patients may undergo a wound evaluation to look for suture extrusion, hematoma, or infection symptoms.

Is There Anything One Can Do to Strengthen the Muscles Damaged by Obstetric Anal Sphincter Injury?

Yes, it is recommended that women who have given birth strengthen their pelvic floor muscles. The repair of an obstetric anal sphincter injury helps strengthen the weakened pelvic floor muscles. The strong, supporting muscles that run from the pubic bone at the front of the pelvis to the base of the spine at the back are known as the pelvic floor muscles. They aid in closing the bladder outlet and back passage and supporting the bladder, womb, and bowel in their proper positions.

Well-toned pelvic floor muscles prevent urine leaks from the bladder and wind or feces from the colon. The pelvic floor muscles relax when the patient passes urine or feces and then contract to regain control. When one coughs or laughs, they actively squeeze to keep from spilling.

Exercising during the first five days will be tough because the area will feel numb and sore, but continue practicing.

Is It Possible to Have a Normal Vaginal Delivery After Obstetric Anal Sphincter Injuries?

Experiencing an obstetric anal sphincter injury during one delivery does not imply that it will happen again during future deliveries. After a successful repair surgery of obstetrical anal sphincter injuries, most women can safely deliver the baby vaginally in a future pregnancy. However, the doctor may suggest a cesarean section (C-section) delivery to prevent future obstetric anal sphincter injuries.

Conclusion

Obstetric anal sphincter injuries are a significant cause of morbidity after vaginal delivery. Few measures can be taken during delivery to diminish the risk of occurrence. Careful examination after every delivery is vital to avoid missing an obstetric anal sphincter injury (OASIS). A close follow-up should be scheduled after the systematic repair of the entire anal sphincter complex. Most women following OASIS can have a vaginal delivery. Post-delivery evaluation of symptoms and anal function testing can help guide the choice of a future mode of delivery.