title: Variability in normative urine flow rates.
abstract: OBJECTIVE
  Parameters derived from uroflowmetry are frequently used in the evaluation and reassessment of children presenting with lower urinary tract dysfunction. Since current nomograms have been constructed from 1 to 2 voids per child, variability of flow parameters is unknown. We evaluate intraindividual variability of flow parameters in children free of lower urinary tract symptoms.
  
  
  METHODS
  Children between 4 and 16 years old (mean age 9.8) who were hospitalized but not suffering from urinary tract infection, pyelonephritis or neurological disturbance, and who had neither structural abnormality of the urinary tract nor acute pain or disorientation voided spontaneously over a flowmeter on 4 to 6 occasions. Post-void urine was estimated by ultrasound within 5 minutes of micturition to confirm complete emptying.
  
  
  RESULTS
  A total of 98 subjects provided a mean of 4.4 traces each. Neither maximum nor average flow rate showed great intraindividual variability (maximum flow rate r >0.8, average flow rate r >0.74). Flow rates significantly correlated with flow duration, volume voided and patient age. Initial flow curves were bell-shaped in 63% of cases, staccato in 30% and intermittent in 6%. These proportions did not change with subsequent voids. There was no significant difference between genders with respect to staccato voiding, although boys demonstrated 70% of intermittent voids and were significantly older than girls.
  
  
  CONCLUSIONS
  In normal children there is minimal variability in flow rates and the phenomenon of staccato voiding is seen approximately 30% of the time, despite no significant levels of post-void residual urine.
authors.affiliation: Department of Surgery, The Chinese University of Hong Kong Prince of Wales Hospital, Shatin, Hong Kong, SAR China. wendybower@cuhk.edu.hk
authors.forename: W F
authors.initials: WF
authors.lastname: Bower
authors.forename: B
authors.initials: B
authors.lastname: Kwok
authors.forename: C K
authors.initials: CK
authors.lastname: Yeung
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D008297:Male; D015588:Observer Variation; D012212:Rheology / Q000706:statistics & numerical data; D014556:Urine; D014563:Urodynamics