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2002 Selected Articles

Obstetric Anal Sphincter Lacerations: An Evidence-based Review
Part 2: Repair Techniques

Rebecca G. Rogers, MD; Dorothy N. Kammerer-Doak, MD

Repair of third- and fourth-degree anal sphincter lacerations has received little attention in obstetrics textbooks and resident education. Most hospital house officers are taught by more senior residents under less than optimal surgical conditions. Exposure and lighting tend to be poor, and sterile technique may not be used. According to a recent survey, fewer than 20% of physicians felt they had received adequate training prior to undertaking their first unsupervised repair of an obstetric anal sphincter laceration.¹ At the authors’ institution, a survey of senior residents reported that they had performed an average of three third- and fourth-degree repairs. The 1993 edition of Williams Obstetrics devotes only one paragraph to the repair of anal sphincter lacerations, describing the end-to-end technique and recommending chromic suture.²

PRINCIPLES

The goal of anal sphincter laceration repair is to restore anatomy by reconstructing the internal anal sphincter (IAS), external anal sphincter (EAS), and perineal body, including reattachment of the distal rectovaginal septum to maintain normal anal function and fecal continence (Figure 1). The general principles are that of any surgical procedure: good visualization, effective analgesia, and adequate assistance. Women may need to be moved from the delivery room to an operating suite to fulfill these conditions. Some experts recommend general or regional anesthesia to achieve sufficient relaxation of the striated muscles of the EAS.³ Without satisfactory muscle relaxation, the torn ends of the sphincter may retract laterally, making identification and repair more difficult.

Figure 1. Perineal anatomy

TECHNIQUE

There are several variations on the method for repairing obstetric anal sphincter lacerations; the following describes the authors’ preferred technique. In patients with a fourth-degree laceration, the rectal mucosa is reapproximated using interrupted fine, delayed, absorbable sutures, such as 3-0 or 4-0 polyglycolic acid (PGA) (Figure 2). Although it has been suggested that these sutures should not penetrate the full thickness of the mucosa into the anal canal to prevent fistula formation, no data support this recommendation. The IAS is then closed using a similar suture in a continuous or interrupted fashion (Figure 3). Irrigation is performed frequently. The IAS is identified as a glistening white fibrous structure between the rectal mucosa and the EAS, and it is often retracted laterally. As the IAS is responsible for the majority of the resting anal tone, the anal canal will begin to resume its normal anatomic shape when the IAS is reapproximated (Figure 4).

Figure 2. Rectal Mucosa	Figure 3. IAS Grasped Above Rectal Mucosa
Figure 4. The IAS in the context of the perineal anatomy Delancey JOL, Toglia MR, Perucchini D. Internal and external anal sphincter anatomy as it relates to midline obstetric lacerations. Obstet Gynecol. 1991;90:924-927.	Figure 5. Overlap of the EAS

The EAS is repaired next with prolonged, delayed, monofilamentous, absorbable sutures, such as 2-0 or 3-0 polydioxanone sulfate (PDS) or Maxon (Figure 5).^3,4 Finally, the second-degree laceration is closed and a perineorrhaphy is performed, including reattachment of the distal rectovaginal septum to the perineal body.

Perioperative care has not been well studied. Many experts recommend administering at least one dose of broad-spectrum intravenous antibiotic during repair, and some surgeons continue oral antibiotics for 1 week following repair.^2-4 Stool softeners, perineal care (eg, sitz baths), and pelvic rest are also common postoperative measures.

The best suture material for anal sphincter laceration repair has not been established. However, several randomized, controlled trials have compared derivatives of PGA, catgut, and nonabsorbable sutures for the repair of episiotomy and perineal lacerations (Table 1).^5-7 The use of PGA was associated with significantly decreased pain and need for analgesia in the immediate postpartum period, as well as decreased rates of dehiscence. Long-term pain and dyspareunia has not been as well studied, and no advantage of one suture over another has been documented.⁷ A disadvantage of PGA reported in some studies was the frequent need for removal of these sutures secondary to "irritation or tightness" (33% versus 12% for chromic suture).⁷ Of note, the majority of these studies were performed in Europe, where mediolateral episiotomies are more common than the midline episiotomy routinely performed in the United States.

The traditional technique for repair of the EAS involves reapproximation of the torn ends using an end-to-end technique.² Historically, this technique was thought to yield good results, but objective evidence and follow-up for these claims are limited.^8,9 More recent objective cohort and case-control studies have reported less-than-optimal results. Following primary repair of obstetric anal sphincter laceration, 30% to 50% of patients complain of anorectal dysfunction, including fecal and flatus incontinence and fecal urgency, and 40% to 50% of these women are found to have disrupted EAS and IAS on physical and ultrasonographic examination.^10-15 Furthermore, anal incontinence symptoms following primary repair of obstetric anal sphincter laceration may increase over time.¹⁶ A prospective study following 94 consecutive cases of obstetric anal sphincter laceration for 2 to 4 years noted an increase in anal incontinence from 17% at 3 months to 42% at 2 to 4 years. While 38% of women with symptoms felt that they needed treatment, only a few had actually sought evaluation due to embarrassment, socioeconomic reasons, or lack of knowledge as to where to obtain help (Figure 6).

Figure 6. Incidence of anal incontinence following traditional obstetric anal sphincter laceration repair.16

The overlapping technique of surgical EAS repair is commonly used to treat anal incontinence months or years after delivery, especially within the field of colorectal surgery.¹⁷ Subjective cure, defined as continence to solid stool, reported with this technique is approximately 80%.^18-20 Despite the good results generally associated with the overlap technique, it is seldom used for primary obstetric anal sphincter laceration repair due to concerns regarding the inability to adequately mobilize muscle to overlap the torn ends and the possibility that suture might cut through freshly torn muscle. Only two studies have addressed the use of this technique. One reported favorable results using the overlapping technique for the primary repair of obstetric anal sphincter laceration in 32 women.³ All repairs were performed in the operating room using aseptic technique under regional or general anesthesia. Incontinence to flatus was subsequently noted in two subjects (8%), and none were incontinent to stool. Ultrasonography demonstrated persistent EAS defects in four subjects (15%). This is in contrast to a previous retrospective study of 50 women by the same group using the end-to-end technique for primary repair of anal sphincter lacerations that noted fecal incontinence in 41% of subjects and separation of the EAS on ultrasonography in 85%(Figure 7).¹⁰

Figure 7. End to End vs. Overlapping EAS

A single randomized, controlled trial has compared the overlapping and end-to-end techniques in 112 women.⁴ Of these subjects, 107 had third-degree lacerations including partial tears, and 5 had fourth-degree tears. At 3-month follow-up, there were no differences between the two groups in perineal pain (36% overlap versus 39% end-to-end, P = 0.9), anal manometry parameters, separation of EAS on ultrasonography (62% overlap versus 70% end-to-end, P = 0.64), and fecal incontinence (49% overlap versus 58% end-to-end, P = 0.46). Daily fecal incontinence to stool was reported by 4% in the overlap group and 9% in the end-to-end group (P > 0.05). This study included any disruption of the EAS, either partial or complete. It is not clear how the overlap technique was used in cases of partial third-degree lacerations.

Given these limited data, there is no obvious superior technique for repair of third-degree obstetric anal sphincter lacerations. However, objective evidence shows unacceptable results with primary end-to-end repair, with 30% to 50% of patients demonstrating separation of the EAS, and fecal incontinence in 20% to 40%.^10-15 Further randomized trials are needed to determine which surgical practices result in better anal continence.

COMPLICATIONS

Morbidity secondary to obstetric anal sphincter lacerations has been analyzed in large retrospective cohort studies and literature review.^21-23 Complications related to third- and fourth-degree lacerations include infection, breakdown or dehiscence, and rectovaginal fistula (Table 2). Reported rates range from 0.5% to 4% for infection (including abscess), 2% to 10% for dehiscence, and 0.3% to 3% for rectovaginal fistula.^21-23

Dehiscence usually presents 2 to 7 days postpartum.^24,25 The most common symptoms are pain and tenderness (65% to 78%), purulent discharge (44% to 65%), fever (44%), and/or passage of stool or flatus per vagina (3% to 73%).²⁵ Infection, defined as fever and/or purulent discharge, has been identified as the etiology in 40% to 80% of dehiscence cases.²⁵ Traditionally, a delay of several months was recommended before undertaking a second surgical reconstruction following anal sphincter dehiscence.²⁶ This waiting period was deemed necessary to ensure adequate vascular supply and optimal tissue viability, although there are no data to support delayed repair. Two retrospective, descriptive studies reported early repair of dehiscence of third- and fourth-degree lacerations after aggressive wound debridement and antibiotic treatment in the presence of infection. Early repair was performed when healthy granulation tissue was noted and infection and purulent exudate had resolved. Patients with fourth-degree dehiscence underwent complete bowel preparation, and received postoperative antibiotics and bowel rest followed by a low-residue diet. Dehiscence or rectovaginal fistula recurred in 6% to 10% of patients following early repair, which is similar to the results of repairs that were delayed for several months after initial dehiscence.^24,25

Delayed morbidity from anal sphincter lacerations includes unrecognized breakdown of the repair, which may or may not be associated with anorectal dysfunction, and anal incontinence. With time, the effects of pudendal neuropathy sustained at vaginal delivery and the aging process may result in progressive neurologic damage leading to anorectal dysfunction years after giving birth. The first birth confers the greatest risk for anal sphincter rupture, with subsequent births contributing to cumulative pudendal nerve damage.^27,28 Fecal incontinence long after delivery may be due to separation of the anal sphincter and/or pudendal neuropathy. Surgical repair using the overlapping technique in women with a separated EAS and intact pudendal innervation results in restoration of continence to solid stool in 75% to 80% of cases and to flatus in approximately 50% of women at up to 15 months’ follow-up.^18-20 However, these results deteriorate with time, as only 50% of patients report fecal continence 5 years after repair.²⁹ Because surgical therapy is successful for the treatment of flatal incontinence in only 50% of cases, conservative therapy is recommended over operative treatment. Therefore, surgical repair is not indicated in an asymptomatic woman with a chronic third- or fourth-degree laceration.

SUBSEQUENT PREGNANCIES

The management of subsequent pregnancies in women with a history of recognized and repaired obstetric anal sphincter lacerations has been addressed in several cohort and case-control studies.^15,16,30-33 Retrospective studies have reported an increased risk of recurrent anal sphincter laceration in subsequent deliveries in women with a history of severe perineal tears as compared with controls.^30,31 More than 5,000 women were analyzed, and the odds ratios for recurrent lacerations in women with past anal sphincter trauma ranged from 2.5 to 3.7. The highest risk for recurrence was noted in women who underwent forceps delivery with midline episiotomy (odds ratio 5.5, 95% confidence interval 2.3 to 13.3, P < 0.001).³¹ This increased risk of severe perineal trauma in subsequent pregnancies suggests an anatomic component, and that midline episiotomy and forceps should not be used in women with a history of third- and fourth-degree obstetric anal sphincter lacerations (Table 3).

Women with temporary or permanent fecal incontinence following anal sphincter laceration and primary repair are at risk for permanent or worsened anorectal dysfunction following subsequent vaginal deliveries.^16,32,33 Women who reported transient anal incontinence after their first delivery and who then gave birth vaginally again, developed permanent anal incontinence in 17% to 40% of cases and temporary symptoms in 39%. In women with anal sphincter lacerations and persistent fecal incontinence after the first delivery, 88% noted deterioration of anal function as assessed by higher fecal incontinence scores after a second vaginal birth.^16,33 In women who had no anorectal symptoms after the first delivery, none experienced permanent incontinence following a second vaginal delivery in one study,³² and 5/46 (11%) had altered fecal continence symptoms.³³ When anal ultrasonography was used to evaluate EAS integrity, 42% of women with occult EAS injuries following the first vaginal delivery developed fecal incontinence symptoms after a second vaginal birth.³³ These authors recommended that cesarean delivery be offered in subsequent pregnancies to women with persistent or temporary fecal incontinence after anal sphincter laceration and primary repair.^16,32,33

CONCLUSION

The anatomic and functional results of primary repair of obstetric anal sphincter laceration are poor. Objective studies report anal incontinence in 30% to 50% of cases, and separation of the sphincter in up to 50%. Thus, preventing third- and fourth-degree anal sphincter lacerations by avoiding the use of forceps and episiotomy when possible is probably the best strategy. Women with a history of anorectal dysfunction following anal sphincter laceration and repair should be offered cesarean delivery in subsequent deliveries to avoid exacerbating the problem. Further research is needed to determine better reparative techniques following obstetric anal sphincter laceration.

Rebecca G. Rogers, MD, is director, Division of Urogynecology and assistant professor of obstetrics and gynecology at the University of New Mexico, Albuquerque. Dorothy N. Kammerer-Doak, MD, is associate clinical professor, Department of Obstetrics and Gynecology, University of New Mexico and urogynecologist, Lovelace Health Systems, Albuquerque, NM.

REFERENCES

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