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Evaluation and Management of a 4th Degree Laceration

Author: Camaryn Chrisman-Robbins, MD

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Mentor:  Eric A. Strand, MD

Editors: Abimbola O. Famuyide, MD and David Chelmow, MD

All women having vaginal delivery should be closely examined for vaginal and perineal injuries and those with any laceration should have rectal examination to determine the extent of their injury prior to surgical repair.  Obstetric anal sphincter injuries (OASIS) encompass 3rd and 4th degree lacerations.  A fourth degree laceration involves the perineal structures, the external anal sphincter (EAS), internal anal sphincter (IAS), and the rectal mucosa.  A rectal buttonhole tear involves the rectal mucosa with an intact sphincter and may be overlooked without a systematic rectal examination. Failure to recognize and properly repair a fourth-degree laceration poses a risk of infection, wound breakdown, anal incontinence, and fistula formation.

Pooled analysis of data involving 15,366 women with OASIS from 22 studies reported an overall rate of 3rd and 4th degree lacerations of 2.4 %.  Operative vaginal delivery with and without episiotomy and midline episiotomy increased the risk of an OASIS laceration substantially.  The odds ratios (OR) with forceps delivery, vacuum-assisted delivery, and midline episiotomy were 5.50, 3.98, and 3.82 respectively.  When forceps were combined with midline episiotomy, the OR for a 3rd degree laceration was 5.65 and for a 4th degree laceration 10.55.  Other risk factors such as primiparity, labor induction and augmentation, persistent occipito-posterior position, and epidural anesthesia also increased the risk with OR in the 2-3 range.

Surgical repair of fourth-degree lacerations requires adequate lighting, adequate anesthesia, appropriate surgical instruments, copious irrigation and meticulous attention to hemostasis for optimal wound reapproximation and healing.  Consideration should be given to performing the repair in an operating room setting.

The rectal mucosa is repaired in a continuous non-locked suture using a monofilament suture such as polydioxanone (PDS®) or a braided suture such as polyglactin (Vicryl®).  Suture size of 3-0 should be used.

If the IAS can be identified separately, it should be reapproximated with interrupted 2-0 Vicryl or 3-0 PDS to reduce the risk of post repair anal incontinence.  To reapproximate the EAS, the separated ends must be isolated and grasped with Allis forceps as they tend to retract laterally. There is inadequate data as to whether end-to-end or overlapping reapproximation of the EAS decreases risk of long-term incontinence. This choice may be left to the surgeon’s preference.  Regardless of approach, either interrupted or of 2-0 Vicryl or 3-0 PDS are typically used.  Permanent suture should not be used on the EAS.

The remainder of the repair to rebuild the perineal body performed like a routine 2nd degree laceration repair.  Rectal examination should be performed after surgical repair to ensure adequacy of sphincter repair and to ensure sutures were not passed through the rectal mucosa.  Prophylactic use of a single dose of cefoxitin or cefotetan administered prior to the repair is reasonable given the consequences of infection and is supported by a randomized trial.

Postoperatively, women should be counseled to maintain a low fiber, low residue diet and take stool softeners for at least 10 days.  Non-steroidal anti-inflammatory agents and acetaminophen are preferred analgesics; oral narcotics should be used with caution because of risk of constipation.  In addition daily Sitz baths and pelvic floor physical therapy may aid in wound healing.  An appointment is advised one or two weeks after discharge with their obstetric provider to ensure there are no signs of wound infection, breakdown, or hematoma formation.

Women should be advised that the prognosis following EAS repair is good, with 60–80% of women having no symptoms of anal incontinence or significant discomfort at 12 months.  Most women who remain symptomatic describe incontinence of flatus or feces or fecal urgency.  After a successful repair, most women can deliver vaginally with a recurrent risk of OASIS between 4% and 8%.  Approximately 2.3 Cesarean deliveries will be required to prevent one OASIS in a woman with prior OASIS.  Patients with persistent incontinence or abnormal endoanal ultrasonography may be offered elective cesarean delivery Risk of occurrence of OASIS may be reduced by controlled head delivery, judicious use of mediolateral episiotomy, in particular for operative vaginal deliveries, and use of warm compress on the perineum and perineal massages during second stage of labor.


Further Reading:

Prevention and Management of Obstetric Lacerations at Vaginal Delivery. Practice Bulletin No. 165. American College of Obstetricians and Gynecologists. Obstet Gynecol 2016;128:e1–15.

The Management of Third- and Fourth-Degree Perineal Tears. London (UK): Royal College of Obstetricians and Gynaecologists (RCOG); Green Top Guideline No 29: June 2015. Accessed via:  Accessed 9/24/17.

Obstetrical Anal Sphincter Injuries (OASIS): Prevention, Recognition and Repair. SOGC Clinical Practice Guideline No 330, December 2015. J Obstet Gynaecol Can 2015;37(12)1131-48.

Pergialiotis V, Vlachos D, Protopapas A, et Al: Risk Factors for Severe Perineal Lacerations During Childbirth, International Journal of Gynecology & Obstetrics, 2014;125:6-14.

Initial approval January 2015; Revised July 2016, Revised November 2017.


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