In our randomized trial of sling placement versus sham placement in women without preoperative symptoms of stress incontinence who were planning to undergo vaginal surgery for apical or anterior prolapse, the odds of urinary incontinence or treatment for urinary incontinence 3 months after surgery among the women in the sling group were substantively reduced, as compared with those in the sham group. The beneficial effect of the sling on urinary incontinence remained significant at 12 months. A benefit was observed regardless of the results of preoperative prolapse-reduction stress testing; there was modest evidence (P = 0.06) to suggest that at 3 months, patients with a positive prolapse-reduction stress test before surgery may have received more benefit than those with a negative test, but this was not apparent at 12 months.
A recent survey study of 132 women who underwent vaginal prolapse surgery and had a negative prolapse-reduction stress test before surgery showed that 42% had postoperative urinary incontinence, as assessed by subjective criteria, which was similar to the 38% rate in our study.15
Moreover, approximately one third of participants who responded to the survey were moderately or greatly bothered by their symptoms, and 5% underwent surgery for these symptoms. These findings highlight the potential role for effective preventive strategies.
Our results support earlier findings of the CARE trial,2
in which the addition of a Burch colposuspension at the time of abdominal prolapse surgery reduced the incidence of postoperative stress urinary incontinence. A smaller randomized trial involving women undergoing vaginal prolapse repair, which was limited to women with occult stress incontinence, showed a 4% rate of incontinence, as assessed by subjective criteria, at 2 years among women who received a sling, as compared with a rate of 36% among women in the control group.5
The absence of blinding in that trial may in part explain the greater observed difference between groups. When the end point includes a subjective component, it is particularly important that participants and outcome assessors be unaware of the study-group assignments.
From the perspective of the individual patient, benefits must be balanced against the higher rates of clinically relevant adverse effects and the need for additional surgery. In our trial, nearly 5% of the women in the sham group underwent a sling procedure in the first 12 months after prolapse-repair surgery. In contrast, surgery to remove the sling was required in only 2.4% of women in the sling group.
Findings in the patient-preference cohort were remarkably consistent with those in the randomized cohort, suggesting that nonparticipation bias probably had a minimal effect on the study findings. Not surprisingly, once women chose to participate in the patient-preference cohort, those with a positive preoperative stress test were more likely to undergo surgery to receive a sling, suggesting that knowledge of the results of the stress test may have influenced the decisions of participants and their surgeons.
The limitations of our study should be considered. It is possible that the incidence of postoperative incontinence may differ according to the type of anterior repair or apical suspension, but our study was not powered to assess these subgroups. Participant knowledge of the study intervention may have had an effect on the subjective outcomes; however, our strategies for masking should have lessened this risk. Some women may have been unwilling to undergo another surgery within the first year, even if they had symptoms. Finally, our findings should not be extrapolated beyond 12 months, although the benefits of sling placement with concomitant prolapse surgery for the treatment of incontinence have been shown to be durable beyond 1 year.16
Adding a midurethral sling at the time of vaginal-prolapse surgery in women without preoperative symptoms of stress urinary incontinence reduces the likelihood of urinary incontinence at 3 and 12 months after surgery but increases the likelihood of adverse events. Counseling of women who are planning to undergo vaginal-prolapse surgery should include attention to both the benefits and the risks of sling placement.