Deep drop: a common finding in uroflowmetry of healthy children and adolescents

Uroflowmetry patterns indicate the presence of a specific lower urinary tract (LUT) dysfunction. However, the definitions for these patterns are mostly descriptive, resulting in poor inter-observer reliability. Irregular and fluctuating flow, which may indicate a staccato flow pattern, is frequently observed in healthy individuals. This study defines "deep drop (DD)" as a "sudden decrease of flow ≥√Qmax or 5ml (whichever is lowest) per second, followed by a rebound of flow ≥ 2ml/s", and investigates the incidence of "DD" in uroflowmetry of healthy children and adolescents. 1787 participants aged 5 to 18 took 3158 uroflowmetry measurements. Uroflowmetry with artefacts (n = 466) and low voided volume (VV) (n = 393) were excluded. 15.8%, 5.9%, and 4.6% of the 2299 uroflowmetry included in the analysis had one, two, and ≥ three DD, respectively. The incidence DD increased from 21.1% at VV < 25% of estimated bladder capacity (EBC) to 41.7% at VV ≥ 115% of EBC. 56.8% of the 734 participants who had two uroflowmetry measurements had no DD on both occasions, while 0.7% had ≥ three DD on both. DD are common in healthy subjects' uroflowmetry. More research is required to determine the validity of this definition and the number of DD required to define the staccato pattern.