uroflowmetry

Uroflowmetry is a noninvasive urological test that measures the rate of urine flow during voiding. It provides quantitative data on how fast urine is expelled and the pattern of flow. A typical study records the voided volume, the time to void, the maximum flow rate (Qmax), the average flow rate (Qmean), and the shape of the flow curve. Post-void residual measurement, when needed, is usually obtained separately by bladder ultrasound or catheterization.

Indications for uroflowmetry include evaluation of lower urinary tract symptoms such as a weak, intermittent, or hesitating stream, difficulty initiating urination, and a sense of incomplete emptying. It is used to help distinguish bladder outlet obstruction from detrusor underactivity, to assess before and after treatment for conditions like benign prostatic hyperplasia, and in general urological workups when voiding function is in question.

Procedure and interpretation involve having the patient void into a calibrated device that plots urine flow rate against time. Adequate voided volume, typically at least 150–200 mL, is required for reliable results. The test is usually performed once the patient is relaxed and able to produce a good effort; repeat testing may occur if results are inconclusive. Key parameters include Qmax and the flow pattern. Normal values depend on age and sex, but a higher Qmax generally suggests normal flow, while a low Qmax with a flattened or plateau-shaped curve may indicate obstruction or reduced detrusor contractility. The test cannot determine the exact cause of abnormal flow and is interpreted alongside symptoms and other assessments, such as urodynamic studies if indicated.

Limitations include variability between tests, dependence on adequate effort and bladder volume, and the inability to diagnose etiologies on its own.