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

Deep drop是健康兒童和青少年尿流速檢測中的常見現象

Lim Li Yi^1,2、Stephen Shei Dei Yang¹

林利憶^1,2，楊緒棣¹

1. Division of Urology, Department of Surgery, Taipei Tzu Chi Hospital, New Taipei, Taiwan （臺北慈濟醫院泌尿科;
2. Unit Urology，Department of Surgery, Hospital Canselor Tuanku Muhriz (馬來西亞囯大醫院泌尿科)

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

Material and Methods: Healthy participants aged 5-18 years were recruited to undergo two uroflowmetry tests. Those who had lower urinary tract dysfunction or symptoms of urinary tract infections were excluded. A “DD” is arbitrarily defined as a “sudden decrease of flow greater than √Qmax or 5ml (whichever is lowest) per second, followed by a rebound of flow ≥2ml/s”. Two reviewers evaluated 100 uroflowmetry curves from the clinic to assess the accordance with the interpretation of “DD”.

Results: There were 3158 uroflowmetry curves from 1787 participants. Uroflowmetry with artefacts (n=466) and low voided volume (n=393) were excluded. Ultimately, 2299 uroflowmetry curves from 1538 participants (mean age 11.5±3.1 years) were included in the analysis. A total of 15.8%, 5.9% and 4.6% of uroflowmetry curves had one, two, and ≥3 DD, respectively. The incidence of ≥1 DD in a uroflowmetry curve increased from 21.1% at voided volume (VV) <25% of estimated bladder capacity (EBC) to 41.7% at VV ≥115% of EBC. Among the 734 participants who had two uroflowmetry tests, only 56.8% of participants had no DD on both occasions, while 0.7% of participants had 3 DD on both occasions.  There was high inter-observer agreement on the number of DDs (k=0.831) in the 100 curves from the clinic.

Conclusion: DD are common in the uroflowmetry of healthy subjects. Its frequency increased as the VV increased. Further research is needed to examine the validity of the current definition and determine the number of deep drops required to define the staccato pattern.