title: It is time to abandon "expected bladder capacity." Systematic review and new models for children's normal maximum voided volumes.
abstract: BACKGROUND
  There is an agreement to use simple formulae (expected bladder capacity and other age based linear formulae) as bladder capacity benchmark. But real normal child's bladder capacity is unknown.
  
  
  OBJECTIVE
  To offer a systematic review of children's normal bladder capacity, to measure children's normal maximum voided volumes (MVVs), to construct models of MVVs and to compare them with the usual formulae.
  
  
  METHODS
  Computerized, manual and grey literature were reviewed until February 2013. Epidemiological, observational, transversal, multicenter study. A consecutive sample of healthy children aged 5-14 years, attending Primary Care centres with no urologic abnormality were selected. Participants filled-in a 3-day frequency-volume chart. Variables were MVVs: maximum of 24 hr, nocturnal, and daytime maximum voided volumes.
  
  
  METHODS
  diuresis and its daytime and nighttime fractions; body-measure data; and gender. The consecutive steps method was used in a multivariate regression model.
  
  
  RESULTS
  Twelve articles accomplished systematic review's criteria. Five hundred and fourteen cases were analysed. Three models, one for each of the MVVs, were built. All of them were better adjusted to exponential equations. Diuresis (not age) was the most significant factor. There was poor agreement between MVVs and usual formulae. Nocturnal and daytime maximum voided volumes depend on several factors and are different.
  
  
  CONCLUSIONS
  Nocturnal and daytime maximum voided volumes should be used with different meanings in clinical setting. Diuresis is the main factor for bladder capacity. This is the first model for benchmarking normal MVVs with diuresis as its main factor. Current formulae are not suitable for clinical use.
authors.affiliation: Department of Urology, Clinic University Hospital of Valencia, Valencia, Spain.
authors.forename: Roberto
authors.initials: R
authors.lastname: Martínez-García
authors.forename: Maria Isabel
authors.initials: MI
authors.lastname: Ubeda-Sansano
authors.forename: Javier
authors.initials: J
authors.lastname: Díez-Domingo
authors.forename: Santiago
authors.initials: S
authors.lastname: Pérez-Hoyos
authors.forename: Manuel
authors.initials: M
authors.lastname: Gil-Salom
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D006801:Humans; D008954:Models, Biological; D012016:Reference Values; D001743:Urinary Bladder / Q000502:physiology*; D014554:Urination / Q000502:physiology*
keywords: adolescent; child; models theoretical and statistical; reference values; symptom assessment; urinary bladder; weights and measures