Study design, materials and methods
Following IRB approval, a retrospective review of consecutive symptomatic women referred with a history of single MUS placement at outside institutions and who underwent a 3DUS before SSR was completed. Women with a history of radiation, GU malignancy, or history of prior sling incision were excluded from analysis. 3-DUS studies were performed using a 3-D high resolution end-fire probe with patients in supine or semi-upright positions. Image processing and interpretation were performed by experienced sonographers/radiologists. MUS location was classified as proximal (within 1 cm of the bladder neck), distal (within 1 cm of the urethral meatus), with the remainder classified as middle. Sling-to-hypoechoic muscle layer distance (SLD) was the shortest distance (millimeters), between the hypoechoic muscle layer of the urethra urethral lumen MUS at the 6 o’clock location. Sling shapes were classified as flat (normal), twisted, curled, or oblique (Figure 1). Primary outcome was requirement for secondary surgery (SS) related to MUS-related sequelae. Two groups were compared, those who did not require additional surgery after SSR (group1) with those who did (group 2).
Results
From 2013 to 2019, 97 of 131 symptomatic women that presented with prior MUS placement met study criteria with a mean follow-up after SSR of 1.93±1.2 years. A second operation for a sling-related sequela was required in 23 women (23.7%) (group 2) (Table 1). There were no statistically significant differences between type of sling, BMI, diabetes, smoking or hysterectomy status or ethnicity between the two groups. The most common symptoms on initial presentation were storage issues (71%), following by voiding dysfunction (63%), dyspareunia (53%), recurrent urinary tract infections (RUTIs) (50%) and finally, pain (50%). Women presenting with RUTIs more often required additional surgery after SSR (p=0.03). On 3-DUS, group 2 women had an average SLD of 3mm (IQR 1.8-3.0mm) compared to 3.8mm (IQR 2.3-5mm) in group 1 (p=0.01). There were no differences between groups in sling shape or location. On multivariate analysis, a history of RUTIs increased the risk of a secondary procedure after SSR (OR 2.9, p=0.05) whereas increasing SLD decreased the risk (OR 0.73, p=0.04). In group 2, an equal number of women required secondary SUI and RUTI procedures (39%), followed by surgery due to persistent outflow obstruction (13%).
Interpretation of results
One in five women will require a secondary operation for sling related sequalae following SSR. This study has shown that a history of recurrent urinary tract infections and depth of sling on 3DUS were predictive for secondary surgeries. Unfortunately, since imaging was performed at a single time point, it is unclear if these slings had been placed deeper than anticipated or if the slings had migrated over time. The increased depth of sling likely influences the risk for outlet obstruction and urethral wall damage resulting, at times, in bladder remodeling and permanent voiding dysfunction. This voiding dysfunction can manifest in several ways, including urinary incontinence and/or RUTIs from incomplete emptying. Even though it did not increase risk, over 40% of women were found to have an abnormal shape of the MUS, which suggests that these slings may not have been either properly placed in the first place or modified by retraction during the healing process.