Uroflowmetry and post-void residual
Checks whether the voided volume is adequate and whether the post-void residual is elevated by ICCS thresholds.
Result
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Formula and thresholds
Expected capacity = (age + 1) × 30 ml (ages 4–12). Measured capacity = voided volume + residual. Residual % = residual / measured capacity × 100. Thresholds: ages 4–6 single > 30 ml or > 21%, repeated > 20 ml or > 10%; ages 7–12 single > 20 ml or > 15%, repeated > 10 ml or > 6%.
Clinical note
For uroflowmetry to be interpretable, the voided volume should be at least 50% of expected capacity; with a small volume the curve and Qmax are unreliable and the test is repeated. Residual urine is measured by ultrasound immediately after voiding (within 5 minutes). A single elevated value should be confirmed by repeat measurement. The result is interpreted with the curve shape (bell, tower, staccato, interrupted, plateau), the bladder diary and symptoms; conclusions are not drawn from Qmax alone.
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