Autologous Platelet Concentrate Bladder Injection for Refractory Overactive Bladder

OAB is clinically defined by urinary urgency, usually with frequency and nocturia, with or without urgency urinary incontinence, and without a clearly identifiable local pathologic, metabolic, or neurologic cause. OAB can substantially affect daily activities, sleep, social participation, and psychological well-being. Standard treatment options include behavioral interventions, oral antimuscarinic agents, beta-3 adrenergic agonists, and third-line therapies. However, some patients have persistent symptoms after first-line and second-line treatment, or cannot tolerate medication adverse effects. These limitations create a need for additional minimally invasive treatment strategies for refractory OAB.

Autologous platelet concentrate / PRP is derived from autologous blood and contains concentrated platelets and bioactive factors. The biological rationale for PRP includes promotion of tissue repair, modulation of chronic inflammation, and potential effects on local nerve function. Preliminary urologic research has explored PRP in bladder-related disorders such as interstitial cystitis / bladder pain syndrome. Based on these properties, bladder injection of autologous platelet concentrate may have potential to improve refractory OAB symptoms by modulating the bladder wall microenvironment and lower urinary tract function.

This is an investigator-initiated, prospective, single-center observational clinical study conducted in the Department of Urology at The First Affiliated Hospital of Chongqing Medical University. The planned enrollment is approximately 50 adult participants with refractory OAB. The study is a self-initiated project. Participants will be recruited through the urology outpatient clinic. No additional recruitment advertisements are planned. Vulnerable populations, including minors, pregnant women, prisoners, illiterate individuals, and persons without full capacity for civil conduct, will not be enrolled.

Screening includes review of medical history, physical examination, confirmation of OAB diagnosis and refractory status, medication history, pregnancy/lactation status when applicable, OAB symptom and quality-of-life questionnaires, and a 3-day 24-hour bladder diary. Clinical evaluation may include blood routine testing including platelet count, coagulation function, liver and kidney function, blood chemistry, blood glucose, urinalysis, urine culture, urinary tract ultrasound, urodynamic evaluation, and cystoscopy as clinically appropriate. Other diseases that may cause OAB-like symptoms, such as urinary tract infection, bladder stone, bladder tumor, interstitial cystitis / bladder pain syndrome, neurogenic bladder, and bladder outlet obstruction, will be excluded before enrollment.

Eligible participants will undergo bladder injection of autologous platelet concentrate / PRP as clinically arranged. Perioperative information will be recorded, including procedure name, date, operator, procedure duration, blood loss, transfusion if any, intraoperative complications, technical details, vital signs, urination frequency, urine volume, wound or procedure-site status, complications, and all adverse events. According to the ethics resubmission form, participants are expected to participate for approximately 24 weeks and complete four visits: before treatment and at 1, 3, and 6 months after treatment. Participants will complete symptom assessments and clinical-data recording. Approximately 20 mL of blood, approximately 50 mL of urine, and some diseased bladder tissue may be collected according to the study arrangement and clinical need. Study data will be managed using unique coded identifiers to protect participant privacy.

Efficacy assessments include OABSS, ICIQ-OAB, OAB-q SF, ICIQ-SF when applicable, 3-day bladder diary measures, 24-hour micturition frequency, urgency urinary incontinence episodes, and urodynamic parameters when available. Safety assessments include all adverse events and complications related to blood collection, PRP preparation, cystoscopic bladder injection, and post-treatment follow-up. Potential events include blood-draw pain or hematoma, vasovagal reaction, infection, PRP preparation failure, urethral or bladder discomfort, hematuria, urinary tract infection, bladder injury, bladder spasm, dysuria, urinary retention, allergic reaction to preparation components, lack of efficacy, and unknown long-term risks.

The primary objective is to evaluate the efficacy and safety of intravesical autologous platelet concentrate injection for refractory OAB. The secondary objective is to explore broader clinical application of autologous platelet concentrate injection. Data will be entered into an electronic database and checked for accuracy and completeness. Continuous variables may be summarized using descriptive statistics and analyzed using t tests, Mann-Whitney U tests, repeated-measures analysis of variance, or linear mixed-effects models as appropriate. Categorical variables may be analyzed using chi-square tests or Fisher exact tests. Safety data will be summarized by adverse-event incidence and event type. A two-sided significance level of 0.05 will be used where applicable.

Inclusion criteria

• Adult participant aged 18 years or older with full capacity to understand the study and provide written informed consent.
• Diagnosis of overactive bladder according to International Continence Society criteria: urinary urgency, usually with frequency and nocturia, with or without urgency urinary incontinence, in the absence of urinary tract infection or another obvious local, metabolic, or neurologic cause.
• Refractory OAB, defined as persistent bothersome OAB symptoms after standard first-line behavioral therapy for at least 3 to 6 months, and inadequate response or intolerance to at least two oral medications with different mechanisms, such as antimuscarinic agents and beta-3 adrenergic agonists, after adequate treatment duration.
• Other possible causes of OAB-like symptoms have been excluded by appropriate clinical evaluation, such as urinalysis, urine culture, ultrasound, urodynamic testing, and cystoscopy when clinically indicated.
• Participant is unwilling, unsuitable, contraindicated, or has inadequate response to existing third-line treatments such as intradetrusor botulinum toxin injection or sacral neuromodulation.
• General condition allows local anesthesia and cystoscopic bladder injection.
• No absolute contraindication to autologous platelet concentrate / PRP treatment.
• Willing to comply with study visits and follow-up assessments.

Exclusion criteria

• Platelet dysfunction syndrome or platelet count less than 50 x 10^9/L.
• Coagulation disorder or current anticoagulant therapy that may increase bleeding risk.
• Active systemic infection or local infection at the injection site.
• Active malignancy or history of malignancy within the past 5 years, especially urinary tract malignancy, or hematologic malignancy such as leukemia or lymphoma.
• Active autoimmune disease judged by the investigator to increase risk or affect interpretation of results.
• Pregnancy or lactation.
• Known allergy to any component used in PRP preparation.
• Untreated urinary tract infection.
• Bladder stone, bladder tumor, bladder outlet obstruction, neurogenic bladder, interstitial cystitis / bladder pain syndrome, or another organic disease that explains OAB-like symptoms.
• Prior intradetrusor botulinum toxin injection or sacral neuromodulation if excluded by the final protocol.
• Severe cardiac, hepatic, or renal insufficiency; uncontrolled diabetes; severe anemia; or other systemic disease that may affect safety or wound healing.
• Psychiatric illness, cognitive impairment, or other condition that prevents understanding of informed consent or reliable follow-up.
• Recent use of nonsteroidal anti-inflammatory drugs or corticosteroids when judged by the investigator to interfere with PRP effect, unless discontinued for an appropriate washout period.
• Expected survival shorter than the study period.
• Refusal to sign informed consent or inability/unwillingness to comply with follow-up.