Clinical Evaluation of the Pelvic Floor Fatigue Index (PFFI)

Background

Ureteral stent-related symptoms are common following ureteroscopy (URS) and retrograde intrarenal surgery (RIRS). Despite similar surgical procedures, stent characteristics, and postoperative management, symptom severity varies considerably among patients. Although trigonal irritation, local inflammation, vesicoureteral reflux, and the mechanical effects of the distal stent have been proposed as contributing mechanisms, these factors do not fully explain the observed interindividual variability.

Pelvic floor muscle function may represent an additional patient-related factor influencing symptom severity. While current assessment methods primarily evaluate maximal voluntary contraction or anatomical movement, no standardized ultrasound-based method is currently available to objectively quantify pelvic floor muscle endurance.

Study Rationale

The Pelvic Floor Fatigue Index (PFFI) was developed to provide an objective, non-invasive, and reproducible ultrasound-based assessment of pelvic floor muscle endurance. The index quantifies the percentage decline in bladder base elevation during a sustained maximum voluntary pelvic floor contraction using suprapubic transverse B-mode ultrasonography.

Unlike conventional pelvic floor assessments that primarily measure maximal contraction, PFFI evaluates the ability to maintain that contraction over time, providing complementary information regarding pelvic floor functional performance.

Study Objectives

The primary objective of this study is to clinically evaluate the Pelvic Floor Fatigue Index (PFFI) by investigating the association between preoperative PFFI measurements and postoperative ureteral stent-related symptoms assessed using the Ureteral Stent Symptom Questionnaire (USSQ).

Secondary objectives include evaluating the reliability of the PFFI measurement method using test-retest analysis and assessing the influence of selected clinical variables on PFFI measurements.

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.