Clinical Evaluation of the Pelvic Floor Fatigue Index (PFFI)

Background: Ureteral stent-related symptoms vary considerably among patients despite similar surgical procedures and stent characteristics. Although several mechanisms have been proposed, the reasons for this interindividual variability remain incompletely understood. Pelvic floor muscle endurance may represent one of the patient-related factors contributing to symptom severity. The Pelvic Floor Fatigue Index (PFFI) is a novel ultrasound-based index developed to quantify pelvic floor muscle endurance by measuring the percentage decline in bladder base elevation during a sustained maximum voluntary pelvic floor contraction using suprapubic transverse B-mode ultrasonography. This prospective observational study aims to clinically evaluate the PFFI by investigating the association between preoperative PFFI measurements and postoperative ureteral stent-related symptoms assessed using the Ureteral Stent Symptom Questionnaire (USSQ). In addition, the study will evaluate the test-retest reliability of the PFFI measurement method and explore its potential role as an objective functional assessment tool for pelvic floor muscle endurance. The findings of this study are expected to provide the first clinical evaluation of the PFFI and establish the methodological basis for future validation studies and broader clinical applications.

Inclusion Criteria: Adults aged 18-65 years. Diagnosis of urolithiasis requiring ureteroscopy (URS) or retrograde intrarenal surgery (RIRS). Planned postoperative double-J ureteral stent placement. Patients belonging to either the Non-pre-stented Group or the Pre-stented Group according to the study protocol. Ability to read and understand the validated Turkish version of the Ureteral Stent Symptom Questionnaire (USSQ). Ability to independently complete the USSQ. Ability to perform an adequate voluntary pelvic floor muscle contraction. Provision of written informed consent. Exclusion Criteria: Clinically significant diabetic neuropathy. Neurological disorders affecting lower urinary tract function (e.g., multiple sclerosis, Parkinson's disease, spinal cord injury). Active lower urinary tract dysfunction (e.g., overactive bladder, neurogenic bladder, interstitial cystitis). Previous pelvic floor surgery. Known urinary incontinence. Urethral stricture. Chronic prostatitis. Recurrent urinary tract infection. Urinary tract malignancy. Advanced chronic kidney disease. Previous upper urinary tract reconstructive surgery. Pregnancy. Active urinary tract infection. Inability to perform an adequate voluntary pelvic floor muscle contraction. Inability to provide informed consent.