This is the prospective randomized parallel groups trial with two participating centers (Department of Urology, Saint Petersburg State University Clinic of advanced medical technologies n.a. N.I.Pirogov, Saint Petersburg, Russia; Department of Urology, Regional Hospital №3, Chelyabinsk, Russia) designed to assess the efficacy and safety of tunable-tension transobturator tape and its ability to reduce the rate of postoperative voiding dysfunction comparing to standard transobturator midurethral sling.

BACKGROUND A minimally invasive midurethral sling procedure is a favorite primary surgical method for the treatment of stress urinary incontinence (SUI). It is considered one of the most effective and safe anti-incontinence surgeries. The observed objective cure rate for transobturator sling is about 90%. However, this number may be wily because in most studies it does not exclude patients who achieved continence, but had voiding dysfunction. It is one of the most common complications of the midurethral sling, associated with the excess tape tension. The estimated rate of postoperative voiding dysfunction is up to 25%. There are few methods that allow to decrease tape tension after the surgery, such as urethral dilatation, sling mobilization, sling incision, complete excision of the tape and urethrolysis. All these methods are invasive, poorly controlled by the surgeon and are associated with the risk of recurrence of stress urinary incontinence.

PREOPERATIVE ASSESSMENT All patients who meet eligibility criteria will undergo a preoperative assessment: a detailed medical history, physical examination, vaginal examination, ICS-Uniform Cough Stress Test (ICS-UCST), uroflowmetry and ultrasound measurement of post-void residual volume (PVR). All patients will complete specific questionnaires, validated in Russia: Urogenital Distress Inventory 6 (UDI-6), International Conférence on Incontinence Questionnaire-Short Form (ICIQ-SF), Pelvic Organ Prolapse/Urinary Incontinence Sexual Questionnaire (PICQ-12). The patients who will answer "Yes" to the question: "Do you experience urine leakage related to the feeling of urgency?" in UDI-6 questionnaire will undergo a urodynamic study to assess the presence and severity of detrusor overactivity.

MATERIALS AND METHODS The hypothesis is that TTT is non-inferior to TOT for SUI treatment. The sample size was calculated assuming an objective cure rate of 85% with TOT using a limit of equivalence of d=0,1 with 80% power. Thus 149 patients in each group are needed. We assume a drop-out rate of 30%, so in total 388 participants will be included in the study.

All enrolled patients will be randomly assigned to TTT or TOT treatment groups in equal ratio the day before the surgery, using computer randomization. The randomization will be performed by one resident urologist, who has no access to patients' data.

All surgical interventions will be performed by 4 urologists, performing at least 100 TOT surgeries per year. The next day after the surgery uroflowmetry values and PVR will be determined in all patients. In case of bladder outlet obstruction (BOO) symptoms, patients from TOT group will be recommended an intermittent self-catheterization for 6 weeks, or a urethral dilatation for choice. Patients from TTT group with BOO will undergo a procedure of non-invasive loosening of the tape under local anesthesia. The algorithm of uroflowmetry, PVR and tuning of the tape will be repeated until normal outflow values will be achieved. Also in patients from the TTT group, ICS-UCST will be estimated. If a patient will be experienced leakage a non-invasive tensioning of the tape under local anesthesia will be performed followed by uroflowmetry, PVR and additional tuning if necessary, until optimal tension will be achieved. The examination will be repeated on the day of discharge.

The postoperative assessment will be performed by 2 urologists, who will be blinded about the type of intervention.

Inclusion Criteria:

• The subject is a woman with stress urinary incontinence or urodynamic mixed urinary incontinence with predominate SUI
• The subject is at least 18 years of age
• The subject has failed conservative treatment for at least 6 months
• The subject gave written consent to participate in the study,

Exclusion Criteria:

• The subject has an active urinary tract infection or skin infection in the region of surgery
• The subject has pelvic organ prolapse (POP) stage 2 or higher according to Pelvic Organ Prolapse Quantification system (POP-Q)
• The subject had prior surgery for SUI or POP
• The subject has predominate urge urinary incontinence
• The subject has a urogenital fistula, anatomical defect, stricture, diverticulum, new growth or any kind of abnormalities of the urethra
• The subject has chronic pelvic pain
• The subject has a system neurological disease, such as Parkinson's disease, Alzheimer disease and other dementias, multiple sclerosis, epilepsy etc
• The subject has pelvic cancer or the subject has undergone radiotherapy for treating pelvic cancer
• The subject has post void residual (PVR) >50 ml
• The subject has dysfunctional voiding and average flow rate (Qave) < 12 ml/s
• The subject is pregnant or disagrees to abstain from the pregnancy during the study
• The subject has any mental disorders affecting his ability to evaluate the risks of the treatment and make an independent decision on participation in the study
• The subject has an allergy on local anesthetics