This nationwide observational study explored changes in SUI symptoms over a 2-year period following POP surgery without concomitant SUI intervention, aiming to understand the impact of postoperative SUI on daily life and identify predictive factors.

Half of the women undergoing POP surgery reported pre-existing SUI. Symptoms resolved or improved after POP surgery alone in half of the cases, and only 5% underwent a procedure for persistent SUI. Improvement was observed after surgery on any compartment, with slightly better outcomes noted in surgeries involving the apical compartment. Severe baseline symptoms predicted persistent SUI, whereas no other variables studied were associated with symptom persistence.

A fifth of the preoperatively continent women developed de novo SUI symptoms, but only 3% experienced bothersome symptoms, and 1% underwent a procedure for it. De novo symptoms occurred irrespective of the compartment or degree of POP. Older age, transvaginal mesh surgery, and baseline urgency urinary incontinence predisposed women to de novo SUI symptoms at both 6 and 24 months after surgery.

International guidelines advocate for the combination of POP and SUI surgery in women with overt or occult preoperative SUI, supported by RCT evidence [12]. However, global rates of concomitant SUI surgery vary widely, ranging from 0.2% in Denmark and 0.8% in this study to 36% in the USA [13, 14]. This variability highlights the limited universal acceptance of this recommendation and reflects diverse patient or surgeon preferences. Limited access to mesh or concerns related to mesh may increase interest in the staged approach, as indicated by the declining rate of concomitant SUI surgery in the USA [14].

In daily practice, a staged strategy results in significantly fewer subsequent SUI procedures than RCTs suggest [6]. We found a 5% risk of subsequent SUI procedures in preoperatively incontinent women and a 1% risk in preoperatively continent women, contrasting with 40% and 6% risks respectively reported in a systematic review [6]. Similar disparity was observed in a recent Danish historical cohort study (N = 15,832), which reported risks of 12% and 2% respectively during the 10 years following POP surgery [13]. The number needed to treat (NNT) with a concomitant mid-urethral sling to prevent one subsequent sling in pre-existing SUI is 2.5 according to RCTs. In our population-based cohort, the NNT settles at around 20. This difference likely arises from RCTs including a SUI procedure in the protocol, whereas in real life, further treatment occurs only if women specifically seek it.

A third of women with pre-existing SUI achieved complete symptom resolution after POP surgery alone, consistent with previous literature (29–52%) [1, 15,16,17,18]. For these women, additional SUI surgery would have been unnecessary. On the other hand, two-thirds experienced persistent SUI, but only 5% underwent subsequent SUI procedures. Financial barriers are unlikely to explain this, as public health care covers expenses in Finland. It is more likely that some women do not expect complete dryness, as supported by a Norwegian RCT, where 21% of women with persistent SUI symptoms declined the planned staged SUI surgery owing to a lack of bother [16]. Cultural factors, surgeons’ preferences, follow-up practices, and concerns about complications may also influence decision-making. Notably, in our study, transvaginal mesh surgery was associated with a higher number of subsequent SUI procedures, despite comparable rates of persistent SUI symptoms, possibly due to patient or surgeon preferences or more rigorous follow-up.

Our observation that high baseline symptom severity is a risk factor for persistent SUI symptoms finds support in a Danish database study (n = 1,657) with a short, 3-month follow-up [15]. Another study (n = 93) did not find this association, but wide CIs indicate a lack of statistical power [18]. Both our study and the Danish study suggest that improved SUI symptoms could be observed after surgery on any vaginal compartment [15]. Additionally, in a Swedish RCT, perineorrhaphy resolved pre-existing SUI symptoms in 44% of women, whereas physiotherapy showed no significant improvement [19]. The biomechanical rationale behind SUI improvement after posterior prolapse repair is not evident. It is possible that pelvic floor muscle function improves when the bulging mass is removed or the reconstructed perineal body provides support for the urethra.

The incidence of de novo SUI varies greatly in the existing literature (4–49%), owing to differences in baseline incontinence status, surgical techniques, the definitions, and follow-up duration [1,2,3,4,5, 20]. In line with our finding of a 20% rate at 2 years, a prospective cohort study from the Netherlands reported a 22% rate of de novo SUI symptoms of any degree at 1 year [1]. However, clinically meaningful de novo SUI is likely better reflected by the rate of bothersome symptoms (3% in this study) or the need for surgical intervention for de novo SUI (1%).

Our finding of consistent de novo SUI symptom rates irrespective of the surgical compartment and degree of prolapse is unexpected. A prevalent theory suggests that advanced anterior prolapse may cause urethral kinking, potentially masking SUI. When this kinking is relieved during POP surgery, de novo SUI may emerge [21]. Consequently, one could anticipate large and anterior dominant prolapses to increase the de novo SUI risk. However, although one study with 164 patients undergoing sacrocolpopexy showed a correlation between the preoperative degree of anterior wall prolapse and de novo SUI [22], other studies support our findings [4, 23, 24]. The interplay between anatomy and incontinence appears to be complex, with bladder neck anatomy possibly more pivotal than cystocele size [25]. Additionally, posterior POP may exert external pressure on the urethra rather than cause urethral kinking. If the continence mechanism is compromised, removing this compression during prolapse surgery could unmask SUI. This notion is supported by a UK study, which found that the lower the descent of the posterior wall after sacrocolpopexy, the lower the incidence of de novo SUI [26].

Accurately predicting de novo SUI has proven to be a challenge. Although occult SUI (i.e., sign of SUI observed only during prolapse reduction) is used as a predictor, its diagnostic accuracy varies across studies [27], and one of the largest studies indicated only a slight improvement over chance [23]. Consequently, it is not a standard practice in Finland. A risk calculator that incorporates stress test results and various patient characteristics [23] offers moderate performance at best, with an area under the curve or concordance index ranging from 0.50 to 0.69 in external validation studies [27,28,29]. Its limited accuracy is understandable, given the weak, non-existent, and even conflicting correlations between its factors and de novo SUI. For example, both our study and a study by Lo et al. identified an increased risk of de novo SUI with advancing age [24], whereas the study on which the calculator was based reported the opposite result [23].

Based on our data, women planning to undergo POP surgery with bothersome SUI symptoms can be informed that without concomitant SUI surgery, they have a 24% chance of complete symptom resolution and a 43% chance of persistent bothersome symptoms, on average. If they are unwilling to accept the higher risk of adverse events associated with a concomitant continence procedure and are comfortable with the possibility of undergoing secondary surgery later, a staged strategy may be appropriate.

As bothersome de novo SUI symptoms develop infrequently and their prediction is difficult, a staged SUI treatment strategy seems a viable option for continent women. Comprehensive preoperative counseling is crucial to prevent misunderstandings should distressing de novo SUI develop.

The strengths of this study include the large, nationwide population, pragmatic setting, prospective data collection, use of a validated questionnaire, and the duration of follow-up. Furthermore, the standard treatment practice in Finland, where the staged strategy is preferred regardless of the preoperative continence status, allowed for the assessment of the impact of prolapse surgery itself.

This study has limitations. The absence of a comparison group hampers the ability to attribute improvements solely to the specific effects of surgery; nonspecific factors such as regression to the mean and the natural progression of the disease may have influenced the outcomes. Additionally, information regarding conservative SUI treatments and repeat POP operations during the follow-up was unavailable. Objective data, such as cough stress tests, frequency volume charts, and urodynamic studies, were lacking, potentially leading to misclassification between SUI and urgency urinary incontinence. Furthermore, there is a possibility that SUI developing against a background of urgency urinary incontinence involves cough-provoked detrusor overactivity. However, a previous report found that responses indicating bothersome SUI in the PFDI-20 (item 17) demonstrate a strong correlation with urodynamic SUI [30]. Although the loss of follow-up was at an acceptable level, it is important to note that this may not occur completely at random. Treatment satisfaction could impact the willingness to reply, potentially introducing bias into the results concerning symptom changes. Nevertheless, the number of subsequent SUI procedures remains unbiased, as these data were available for all except one participant. The clinical evaluation by multiple doctors may have introduced heterogeneity into the POP-Q measurements. Finally, although the population-based setting ensures diverse patients, surgical techniques, and surgeons, thereby enhancing external validity, the predominantly white and culturally homogenous study population may limit the generalizability of the results to other ethnic groups.