All 266 women (mean age 61 years) had preoperative UDS tracing, surgical and follow-up data available for analysis. Preoperative UDS revealed a mean: Pdet@Qmax 22 cmH2O (IQR 12-30), Qmax 18 mL/s (IQR 11-23), capacity 529 mL (IQR 370-659, σ=207), PVR 120 mL (IQR 5-160). The third tertile cutpoint for large capacity bladder was >600 mL (33%, n=88). Women with prolapse [POP-Q Stage: I (n=14), II (n=120), III (n=118), IV (n=14)] underwent anterior-only (n=115), apical-only (n=41) or combination anterior-apical (n=110) prolapse repair. Sling placement was performed in 56% (n=150) patients at time of prolapse repair. Comorbid conditions included diabetes (14%), hyperlipidemia (34%), neuropathy (6%), obesity (17%), and UTI (45%). Following prolapse repair, 239 out of 266 patients had a follow-up PVR recorded. There were a total of 519 PVR values recorded at up to 2,949 days (mean 395, σ=659) and 9 time points (median 2, IQR 1-3) after surgery. Mean PVR at longest follow-up was 66 mL (σ=120).
On univariate analysis, large capacity bladder >600 mL was associated with a younger age (mean 57 vs. 63 years; p<0.001) at time of prolapse repair. There was no significant difference in the proportion of large bladders with diabetes (p=0.508), hyperlipidemia (p=0.259), neuropathy (p=0.206), obesity (p=0.613) and UTI (p=0.387). POP-Q stage 3+ prolapse tended to occur in large bladders (57 vs. 46%; p=0.099). On UDS, large capacity (vs. <600 mL) had a mean: capacity of (763 vs. 413 mL; p<0.001), Pdet@Qmax (22 vs. 21 cmH2O; p=0.611), Qmax (20 vs. 17 mL/s; p=0.065), PVR (208 vs. 76 mL; p<0.001), VE (73 vs. 81%; p=0.027). There was no difference in prolapse stage or type of repair for large versus <600 mL capacity bladders. A similar proportion of large (vs. <600 mL) bladders underwent sling placement at time of prolapse repair (n=44/88 vs. 106/178; p=0.139). Follow-up PVR revealed a significantly elevated PVR in all patients with large bladder (23% >100 mL, p=0.038; 15% >200 mL, p=0.003; 11% >300 mL, p=0.001), however 44% of patients with a large (vs. <600 mL) bladder had a PVR improvement of >100 mL (n=39/88 vs. 50/178; p=0.008) on longest follow-up when compared to their pre-operative PVR.
In order to characterize changes in PVR over time and identify pre-operative patient characteristics associated with incomplete emptying after prolapse repair, longest follow-up PVR >200 mL was used to define elevated PVR after surgery. The 27 women with no recorded follow-up PVR were excluded from PVR analysis. On univariate logistic regression (Figure 1) for the response variable longest follow-up PVR >200 mL, the following factors were associated with elevated follow-up PVR: UTI (OR 3.85; CI 1.36-10.90; p=0.011), capacity >600 mL (OR 3.74; CI 1.48-9.46; p=0.005), and pre-operative PVR >100 mL (OR 3.01; CI 1.21-7.47; p=0.018), >200 mL (OR 2.82; CI 1.10-7.28; p=0.031), >300 mL (OR 4.44; CI 1.54-12.90; p=0.006). Specific thresholds for pre-operative factors associated with longest follow-up PVR >200 mL included increased capacity (mean 647 vs. 518 mL), elevated pre-operative PVR (mean 231 vs. 105 mL), and poor VE (mean 66 vs. 80%). On stepwise backward logistic regression, our final multivariate model identified UTI (OR 3.74; CI 1.31-10.72; p=0.014) and capacity >600 mL (OR 3.64; CI 1.42-9.34; p=0.007) as independent factors associated with longest follow-up PVR >200 mL (AUC=0.727). Pre-operative capacity was assessed as a continuous variable, for the outcome longest follow-up PVR >200 mL, with a capacity cutpoint of 600 mL located at the left upper corner of the ROC (AUC=0.673). As a categorical value, the AUC was 0.658. To look at the association between time and longest follow-up PVR, we applied Kaplan-Meier cumulative incidence function methods (event = longest follow-up PVR >200 mL). Using this approach, UTI was associated with a higher proportion of patients with a PVR >200 mL at most recent follow-up, however the confidence interval included the null association (HR 1.81; CI 0.69-4.75). On Kaplan-Meier analysis for pre-operative capacity (Figure 2), a capacity >600 mL was significantly associated with a higher proportion of patients with PVR >200 mL at most recent follow-up (HR 3.60; CI 1.50-8.63).