Although stress urinary incontinence (SUI) is a very common condition, its pathophysiology has not been clearly elucidated. Therefore, the cases of failure after anti-incontinence procedures are difficult to explained. Interestingly, the point of insertion of the sub-urethral slings has evolved through time: from 0.5 cm from the external urethral orifice (EUO), to 1 cm from the EUO, to the ‘1/3 rule’ from the EUO, and currently to the half of the length of the urethra, although there are authors suggesting even more proximal to the internal urethral orifice (IUO) insertion of the sling [1]. 
Urethral motion profile (UMP) is a sonographic modality that assists in the assessment of urethral mobility. The urethra is divided into six equidistant points from the bladder neck to the EUO, and their mobility is calculated with measurements at rest and at maximum Valsalva maneuver. Increased UMP appears to be associated with SUI [2].
The evaluation of the placement of the sling in relation to the UMP and the distances from the EUO and the IUO is a concept that has not been studied in depth. The aim of this study was to pre-operatively calculate the UMP in SUI patients, and then investigate the relationship of the tape position post-operatively with the successful outcome.

Data from a prospective cohort study that was conducted from December 2019 to January 2023 were obtained. Consecutive patients treated with SIMS for SUI were included. The patients presented with SUI, and they were initially examined in the outpatient department [history, POP-Q, cough stress test, urodynamic exam, and pelvic floor ultrasound (PFUS) including UMP]. Patients with elvic organ prolapse and previous incontinence surgery were excluded. The patients were evaluated 3-6 months post-operatively with a clinical examination that included stress test, PFUS including evaluation of the tape position and the tape mobility, and incontinence questionnaires (PGI-I, PGI-S, ICIQ-SF). Statistical analysis was performed with Microsoft EXCEL.

Data from 9 women who underwent single-incision mid-urethral sling for SUI were used for this study. Three of these patients had positive stress test (failed procedure / Group F) and another 6 with negative stress test (matched at age and weight) were depicted as the control group (Group C). Demographics are depicted in Table 1. Group F had higher pre-operative Qmax and Qave at uroflowmetry. Regarding pre-operative sonographic parameters, Group F had significantly lower mobility in Points 1-4 in the UMP, and overall lower mobility in all UMP points. The post-operative sonographic assessment indicated that sling placement was marginally peripheral in Group F compared to Group C (20.9 to 20.2mm in relation to bladder neck and sling placement at 2.5 compared to 2.7 quadrant).

Failed slings were associated with higher Qmax and lower UMP. This is in accordance with the generally accepted notion that slings increased success rates in women with well mobile urethra compared to women with limited mobility urethras. Ultrasound has the advantages of a non-invasive method that can be studied with high technology instruments in order to provide in-depth analysis.

Sonographic assessment of the urethral mobility remains an under investigated area. Pre-operative evaluation of the UMP could indicate possible sling failures.

Pirpiris A, Shek KL, Dietz HP. Urethral mobility and urinary incontinence. Ultrasound Obstet Gynecol 2010; 36: 507-511.
Bergstrom BS. Urethral hanging theory. Neurourol Urodyn 2017; 36: 826-827.
Bergstrom BS. Stress urinary incontinence is caused predominantly by urethral support failure. Int Urogynecol J 2022; 33: 523-550.