Deep drop in uroflowmetry of healthy children and adolescents

Uroflowmetry is useful in the evaluation of patients with suspected lower urinary tract dysfunction (LUTD). The pattern may serve as a guide to a specific condition, so it is critical to interpret it accurately and consistently. There are various definitions for staccato patterns, but they are primarily descriptive and result in low inter-observer reliability. Some authors stated that a staccato pattern must include a specific amount of "deep drops," "notches," "peaks," and "fluctuations." However, our observations show that these features are common even in uroflowmetry curves of healthy individuals.

To propose comprehensive criteria for defining "deep drop (DD)", assess the incidence of DD in uroflowmetry curves of healthy children and adolescents, and to evaluate the inter-rater agreement for this new definition.

This study defines DD as a "sudden decrease of flow ≥√Qmax followed by a rebound of flow ≥2 ml/s". 1787 participants, aged 5-18 years, took 3158 uroflowmetry measurements. Uroflowmetry with artefacts (n = 466) as illustrated in the Supplementary Figure and low voided volume (VV) (n = 1425) were excluded.

Of the 1267 uroflowmetry curves included in the analysis, 16.0 %, 7.4 % and 7.3 % had one, two, and ≥three DDs, respectively. The incidence of any DD increased from 26.1 % at VV 50-75 ml of estimated bladder capacity (EBC) to 51.2 % at VV >150 % of EBC (see Supplementary Table). Excluding uroflowmetry with large voided volume (LVV), the incidence of deep drops decreased to 15.7 %, 6.7 %, and 5.2 % for one, two, and three deep drops, respectively. Among 261 participants with two uroflowmetry measurements, 53.3 % had no DD on both occasions, while 4.6 % and 1.5 % had ≥ two and ≥three DDs on both occasions, respectively.

DDs are common in the uroflowmetry of healthy subjects, but ≥2 DDs are uncommon. Based on these findings, the occurrence of ≥2 DDs on uroflowmetry, particularly if observed repeatedly, may warrant further evaluation for possible LUTD. Further research is needed to determine the validity of the DD definition and number of DD required to define the staccato pattern by correlating the urodynamic findings of patients with DD.