Repair of the external anal sphincter after an obstetric perineal laceration may be followed by a period of less than ideal anal continence. High rates of anal incontinence after surgery may be related to external anal sphincter defects. Sultan et al1 reported external anal sphincter defects in 82% of women 7 weeks after primary repair of an anal sphincter tear compared with 33% in women who did not have a sphincter tear. Their findings suggested that traditional end-to-end surgical repair of external anal sphincter defects did not restore normal anatomy or function. Subsequently, they published a small retrospective case series in which overlapping repair was performed in an operating room under regional or general anesthetic in 32 women using polydioxanone suture. At 5 months postpartum, only two (7%) women had flatal incontinence and none had fecal incontinence. Because of this work, the investigators recommended that the overlapping rather than end-to-end technique be used to repair obstetric injuries of the external anal sphincter.2 In a randomized trial of primiparous women who underwent either an end-to-end or an overlapping repair of a third-degree or fourth-degree tear of the external anal sphincter (external anal sphincter), we found that both flatal and fecal incontinence rates at 6 months after repair were higher in women who underwent an overlapping repair.3 Six randomized trials examining this question have been published in the literature.3 – 8 Four of the studies showed no advantage of one method of repair over the other for the prevention of fecal incontinence. The findings of the other two studies were based on small samples. The longest follow-up reported to date has been 12 months. This report represents a 3-year follow-up of our study patients.
MATERIALS AND METHODS
The details of the materials and methods used in this study have been previously published.3 This study was conducted in a single tertiary care academic center. Between 2001 and 2007, women who sustained an obstetric third-degree or fourth-degree laceration were enrolled in the study. Women with partial tears of the external anal sphincter and multiparous women have been excluded from the present analysis. The state of the internal anal sphincter was not considered as an inclusion criterion, but any internal anal sphincter defects identified at surgery were repaired. The research protocol was reviewed and approved by the Izaac Walton Killam Health Center institutional review board.
The sample size calculation was based on previous research in our center that found that 47% of primiparous women who sustained a third-degree or fourth-degree perineal laceration experienced flatal incontinence.9 In the retrospective series by Sultan2 of primary overlapping repair, the rate of flatal incontinence was only 7%. To detect a difference between a 50% rate of flatal incontinence and a 25% rate with a power of 80% and an alpha of 0.05, 60 participants were required in each study group. A two-tailed test and two-sided confidence interval for the difference in flatal incontinence rate were planned in reporting the results. Anticipating a drop-out rate of approximately 20%, we proposed to enroll a sample of 150 primiparous women, with 75 women in each treatment arm. An interim analysis was planned to occur when the primary outcome would be known for 50% of the patients. To preserve the 0.05 alpha level, we used an O'Brien-Fleming decision rule whereby statistical significance would be declared if either P<.006 was found at the interim analysis or P<.048 was found at the final analysis.10
Eligible women were randomized to receive either overlapping or end-to-end external anal sphincter repair using a variable block size (2, 4, or 6) to prevent the ability to predict the group to which the next patient would be assigned. Each randomization required logging into a secure, password-protected website accessed through a computer terminal in the birth unit. The allocation sequence was determined by a computer algorithm developed by Dalhousie University Computer Services, which also created the website. All study investigators, including the statistician, were blind to the allocation code until the final analysis. The interim analysis, with repair groups labeled A and B, was presented by the statistician to an independent oversight committee whose task was to review any adverse events and instruct the investigators to either stop or continue the study.
Women were consented in two steps. The initial consent was for randomization to one of the repair groups. Surgeons were asked to indicate at the time of repair if defects in the internal anal sphincter and the anal mucosa were present. A tear which included the internal anal sphincter was classified as 3c and one that included the anal mucosa was classified as a 4th degree tear.6 The day after the procedure, participants were approached by our research nurse for consent to the 6-month clinical follow-up and questionnaire follow-up for 3 years. Ethically, we believed, and our institutional review board agreed, that patients were not in a position to provide informed consent to the additional burden of long-term follow-up considering the time and emotional constraints at the time of delivery. The two steps were necessary to allow women to make the decision about involvement in the follow-up investigations under less stressful conditions.
The women were blinded to the surgical procedure performed and were advised as part of the consent process that blinding was necessary to avoid biasing the results. The health care personnel who performed the clinical follow-up evaluations were also blinded and did not have access to the women's charts at any time during the study.
At the beginning of the study, a grand rounds presentation on the study design and surgical techniques was given. Teaching sessions for the residents and staff were performed every 3 months to review the surgical technique. The training was designed to eliminate any confounding attributable to surgeon inexperience with either method of repair. The principal obstetric researchers made themselves available during the first year of the study to act as preceptors during the repairs.
The surgical repair and perioperative care are described in a previous publication.1 The procedures were judged to be of comparable surgical difficulty. Our research nurse subsequently abstracted additional relevant obstetric data from the medical record.
The long-term follow-up included completion of the incontinence questionnaire. This questionnaire was adapted from the Fecal Incontinence Quality of Life scale11 to make it a more disease-specific and age-specific instrument.12 The questions used to elicit the outcomes of flatal and fecal incontinence required a yes or no answer. For flatal incontinence we asked, “During the past 4 weeks, have you experienced involuntary passing of flatus from the rectum (passing gas when you did not want to)?” For fecal incontinence, we asked, “Over the past 4 weeks have you experienced involuntary leaking or soiling of stool (feces) from the rectum?” Additional questions were designed to determine the frequency and quantity of flatal or fecal incontinence and to determine if the condition had remained the same, deteriorated, or improved since delivery. A 45-item quality of life instrument12 specific to anal incontinence was also administered to those women who indicated that they had experienced anal incontinence.
Participants were asked to indicate if they had had to see a physician for problems since their surgical repair; whether they were currently breastfeeding; and whether they were performing Kegel exercises. A four-question pain index was used to enquire about pain at the repair site and dyspareunia. Finally, women were asked to indicate if they were experiencing feelings of sadness, discouragement, or hopelessness during the month before answering the questionnaire.
Several approaches to the treatment of losses to follow-up were considered. One approach involved carrying forward the most recent nonmissing value. This would have led to the conclusion that a difference, if found, had lasted longer than was actually the case. Another approach involved interpolation of missing values. We also performed a sensitivity analysis with missing values assumed to reflect first a favorable outcome (continence) and then an unfavorable outcome (incontinence). All of these approaches led to similar conclusions. Two facts were clear from all of these approaches: 1) incontinence rates declined with increasing time since surgical repair and 2) incontinence rates were not significantly different between the two types of repair at 2 and 3 years after surgical repair. This led to the decision to substitute the next nonmissing response in place of missing responses whenever a subsequent nonmissing response was available. Regarding the treatment of permanent losses to follow-up, we report only the analysis with losses to follow-up treated as missing subsequent to the last follow-up. Thus, this was essentially an analysis of the responses received. The rationale for this was that the study coordinator had been able to establish in nearly every instance that the nonresponder was no longer residing at the address she had provided.
Statistical analysis was performed using SPSS 16 and SAS 9.2. Specific methods of data analysis to compare baseline characteristics and outcomes in the two surgical repair groups consisted of χ2 tests for categorical variables, t tests for continuous variables, and logistic regression to adjust for covariates.
Figure 1 illustrates the enrollment and follow-up of women. Six hundred seventy-one women were assessed for eligibility. Four hundred ninety-seven women were excluded: 416 did not meet inclusion criteria (most commonly because they did not have a complete third-degree tear), 28 refused participation, and 53 were not included for other reasons, which included physician decisions concerning other contraindications. One hundred seventy-four women were randomized, 86 to an end-to-end repair and 88 to an overlapping repair. Eleven women were excluded after randomization for incomplete sphincter tears. Fifteen women either declined follow-up or were lost to follow-up in the first 6 months. Twenty-five were excluded because they were multiparous women. One hundred twenty-three women completed the 6-month questionnaire, 62 in the end-to-end group and 61 in the overlapping group. One hundred four women (54 in the end-to-end and 50 in the overlapping groups, 85%) of this study group completed the 1-year follow-up questionnaire. At 2 years, 95 women completed the questionnaires (48 end-to-end and 47 overlapping) for a 77% return rate. At 3 years, 68 women completed the questionnaire (31 end-to-end and 37 overlapping), for a 55% return rate. There were no significant differences in demographic or obstetric variables between women who responded to follow-up and those who did not.
Table 1 examines the maternal and newborn characteristics of the study groups. There were no significant differences in these characteristics. Table 2 shows the baseline delivery characteristics of the study groups. All deliveries were of singletons and all were delivered in vertex presentation. Eighty-nine percent of newborns were delivered in the occiput anterior position, 7% were in the occiput posterior position, and 4% were in the occiput transverse position. The majority of women, 99 (80%), had epidural anesthesia during labor and delivery. There were no significant differences in the delivery characteristics, although by chance there happened to be a few more cases of disrupted rectal mucosa in the overlapping repair group.
The incontinence rates at each time point are summarized in Tables 3 and 4. The primary overall flatal incontinence rate at 1 year was 43%. The rate for end-to-end repair was 31%, and for overlapping repair it was 56%. The difference is 25% (95% confidence interval 6%–43%, P=.012). The primary overall fecal incontinence rate at 1 year was 12%. The rate for end-to-end repair was 7%, and for overlapping repair it was 16% (P=.17). The difference is 9% (95% confidence interval −4% to 21%). Differences in the rates of incontinence between the two surgical repair groups had all but disappeared by the end of year 2.
Eighty-five (69%) of our study participants underwent a subsequent delivery; however, only two women, one in each group, had a subsequent delivery before, or at approximately the time of, the 1-year follow-up questionnaire. When their data are excluded from the 1-year analysis, the rates of flatal incontinence are 31.5% for end-to-end repair and 57.1% for overlapping repair (P=.009); for fecal incontinence, the rates are 7.4% for end-to-end repair and 16.3% for overlapping repair (P=.16).
Disruption of the rectal mucosa was not found to be associated with either flatal or fecal incontinence in our data. Not surprisingly, therefore, adjustment for a disrupted rectal mucosa and for the other obstetric and demographic factors using logistic regression did not affect the conclusions of this analysis.
Our study finds that the overlapping repair is more likely to result in anal incontinence than the more traditional end-to-end repair. This difference was found at 1 year, the time when loss to follow-up was least likely to affect the accuracy of the results. This is the first trial to enroll exclusively primiparous women with complete tears of the external anal sphincter and to follow-up these women for a significant time interval after treatment. The results of this report confound previous studies that found either a benefit to an overlapping repair or no difference in the two procedures.
Traditional obstetric practice has been to repair external anal sphincter defects using an end-to-end technique. The publications by Sultan that reported higher rates of external anal sphincter defects and associated anal incontinence symptoms after repair using the traditional end-to-end technique prompted concern among clinicians and a shift in practice toward performing an overlapping repair of obstetric anal sphincter lacerations.13
Six trials comparing the overlapping to end-to-end repair techniques have been published.3 – 8 A Cochrane review of three of the previous trials found no difference in flatal or fecal incontinence rates between surgical groups but did find a lower rate of fecal urgency and a lower overall anal incontinence score in the overlapping group. It also found no difference in quality of life between groups.14 The Cochrane review authors conclude that “immediate primary overlapping repair appears to be associated with reduced risk for fecal urgency, anal incontinence score, and deterioration of anal incontinence symptoms.” The authors acknowledge that these conclusions were based on the trial by Fernando et al,6 involving only 64 women, that was published by the same group who performed the meta-analysis for the Cochrane review. The authors also concluded that the total number of women in the trials they reviewed, 279, was too small to permit meaningful conclusions.
Since this Cochrane review was published, two additional trials have been published.3,8 A total of 571 women have been enrolled in the six randomized trials. Although a recent review pointed out shortcomings in all of these studies,15 the fact remains that a substantial body of evidence now exists. Four of the studies with enrolments of more than 100 women found no beneficial effect of one surgery over the other on fecal incontinence rates.3 – 5,8
This study is limited by the loss to follow-up that often occurs in younger populations that frequently change their place of residence. Using the raw data without accounting in any way for loss to follow-up, we did not find a significant difference in anal incontinence rates at 2 and 3 years. Although the loss to follow-up was not large at 1 year, it became significant at the 2- and 3-year follow-up intervals. Some of the women in this study underwent subsequent deliveries. If some of these deliveries precipitated anal incontinence, then this could have masked the long-term effect of the repair technique used for their external anal sphincter tear.
Although it appears that the higher rate of anal incontinence in the overlapping group at 1 year was not sustained over a longer follow-up period, we believe that the higher rate of anal incontinence at 1 year is an important concern. If obstetricians can reduce the rate of anal incontinence, even for 1 year, then this will have a significant effect on the quality of life of women who sustain third-degree and fourth-degree obstetric lacerations of the external anal sphincter muscle.
Although the introduction of the overlapping repair for third-degree or fourth-degree tears of the external anal sphincter sustained at obstetric delivery was intended to reduce the incidence of anal incontinence, particularly fecal incontinence, there is now a significant weight of evidence that shows no benefit from using this surgical procedure. Obstetricians must weigh the importance of the higher rate of flatal incontinence found with the overlapping repair in the first year of follow-up on their patients' quality of life. Longer-term evidence from this study, although compromised by loss to follow-up, shows no advantage of one procedure over the other.
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© 2012 by The American College of Obstetricians and Gynecologists. Published by Wolters Kluwer Health, Inc. All rights reserved.
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