ABSTRACT:

Purpose: Caffeine restriction is frequently recommended in men with lower urinary tract symptoms (LUTS), although evidence regarding its acute effects on objective voiding parameters is limited. We evaluated the short-term impact of single-dose caffeine intake on uroflowmetric outcomes.

Materials and methods: In this retrospective study, 156 men with LUTS underwent paired uroflowmetry measurements under standardized conditions before and 60 min after ingestion of 200 mL filtered coffee containing 100 mg caffeine. Maximum urinary flow rate (Q_max), mean flow rate (Q_mean), and post-void residual (PVR) volume were assessed. Subgroup analyses were performed according to baseline Q_max, prostate volume, body mass index, and symptom severity. A separate group of 127 patients undergoing repeated uroflowmetry without caffeine exposure was analyzed to assess measurement variability.

Results: Mean Q_max increased from 16.12 to 18.33 mL/s (mean difference 2.21 mL/s; p = 0.010; Cohen's d = 0.33). Q_mean increased significantly (p = 0.003), while PVR remained unchanged. A clinically meaningful improvement (ΔQ_max ≥ 3 mL/s) occurred in 34.8% of patients. Greater improvement was observed in patients with baseline Q_max ≥ 10 mL/s (p = 0.036). No significant differences were detected according to prostate volume or obesity status.

Conclusions: Acute caffeine intake resulted in a small but significant increase in urinary flow without worsening residual urine. These findings suggest that short-term caffeine exposure does not adversely affect objective voiding dynamics in men with LUTS.