This study will look at how well a measure called the Qmax/eGFR ratio is related to the severity of urination problems in men over the age of 40. Qmax is a test that shows how fast a person can urinate, and eGFR is a number that reflects kidney function. Men who have urinary symptoms will be asked to do a urine flow test, a blood test, and fill out a questionnaire about their symptoms and quality of life. We will study if there is a link between the Qmax/eGFR ratio and how severe their symptoms are. The results may help doctors better understand how kidney and urinary function are related in men with these problems.

This prospective observational study aims to explore the clinical relevance of the Qmax/eGFR ratio in men over 40 years of age presenting with lower urinary tract symptoms (LUTS). Qmax, derived from uroflowmetry, reflects bladder emptying function, while eGFR represents renal filtration capacity. While both parameters are routinely measured in clinical practice, their combined predictive or associative value in LUTS severity has not been well defined.

Participants will undergo standard non-invasive assessments including uroflowmetry, serum creatinine testing (for eGFR calculation), and will complete the International Prostate Symptom Score (IPSS) questionnaire. The IPSS includes both total symptom score and quality of life (QoL) component. The primary objective is to evaluate the correlation between the Qmax/eGFR ratio and IPSS total score. Secondary objectives include the relationship between Qmax/eGFR and QoL scores, as well as analysis based on prostate volume categories.

This study seeks to identify whether the Qmax/eGFR ratio may serve as a composite marker reflecting both voiding efficiency and renal function in the clinical assessment of LUTS, potentially supporting more individualized decision-making in urological practice.

Inclusion Criteria:

• Male patients aged 40 years or older presenting with lower urinary tract symptoms (LUTS)
• Able to provide informed consent
• Willing and able to undergo uroflowmetry and blood testing
• Able to complete the IPSS questionnaire, including the QoL item
• Estimated glomerular filtration rate (eGFR) ≥ 30 mL/min/1.73m²

Exclusion Criteria:

• History of urological surgery (e.g., prostatectomy, bladder surgery)
• Diagnosed or suspected prostate cancer
• Active urinary tract infection (based on clinical symptoms or urinalysis)
• Neurological conditions affecting bladder function (e.g., Parkinson's disease, spinal cord injury)
• Presence of an indwelling urinary catheter at enrollment
• eGFR < 30 mL/min/1.73m²
• Inability to perform uroflowmetry or complete clinical evaluations

Male outpatients aged 40 years or older who present with lower urinary tract symptoms (LUTS) to the urology clinic. Participants will be evaluated during routine clinical visits and must be capable of completing symptom questionnaires and undergoing non-invasive tests such as uroflowmetry and blood sampling. The study population is drawn from a single tertiary academic medical center.

Individual participant data (IPD) will not be publicly shared due to the observational design, single-center setting, and the absence of genomic or identifying information. However, anonymized data may be made available upon reasonable scientific request and after appropriate ethical and institutional approvals.