title: The impact of temperature and urinary constituents on urine viscosity and its relevance to bladder hyperthermia treatment.
abstract: OBJECTIVE
  The aim of this study was to determine the kinematic viscosity of human urine and factors associated with its variability. This value is necessary for accurate modelling of fluid mechanics and heat transfer during hyperthermia treatments of bladder cancer.
  
  
  METHODS
  Urine samples from 64 patients undergoing routine clinical testing were subject to dipstick urinalysis and measurement of viscosity with a Cannon-Fenske viscometer. Viscosity measurements were taken at relevant temperatures for hyperthermia studies: 20 °C (room temperature), 37 °C (body temperature), and 42 °C (clinical hyperthermia temperature). Factors that might affect viscosity were assessed, including glucosuria, haematuria, urinary tract infection status, ketonuria and proteinuria status. The correlation of urine specific gravity and viscosity was measured with Spearman's rho.
  
  
  RESULTS
  Urine kinematic viscosity at 20 °C was 1.0700 cSt (standard deviation (SD) = 0.1076), at 37 °C 0.8293 cSt (SD = 0.0851), and at 42 °C 0.6928 cSt (SD = 0.0247). Proteinuria appeared to increase urine viscosity, whereas age, gender, urinary tract infection, glucosuria, ketonuria, and haematuria did not affect it. Urine specific gravity was only modestly correlated with urine viscosity at 20 °C (rho = 0.259), 37 °C (rho = 0.266), and 42 °C (rho = 0.255).
  
  
  CONCLUSIONS
  The kinematic viscosity of human urine is temperature dependent and higher than water. Urine specific gravity was not a good predictor of viscosity. Of factors that might affect urine viscosity, only proteinuria appeared to be clinically relevant. Estimates of urine viscosity provided in this manuscript may be useful for temperature modelling of bladder hyperthermia treatments with regard to correct prediction of the thermal conduction effects.
authors.affiliation: Division of Urology, Duke University Medical Center, Durham, NC 27710, USA. brant.inman@duke.edu
authors.forename: Brant A
authors.initials: BA
authors.lastname: Inman
authors.forename: Wiguins
authors.initials: W
authors.lastname: Etienne
authors.forename: Rainier
authors.initials: R
authors.lastname: Rubin
authors.forename: Richmond A
authors.initials: RA
authors.lastname: Owusu
authors.forename: Tiago R
authors.initials: TR
authors.lastname: Oliveira
authors.forename: Dario B
authors.initials: DB
authors.lastname: Rodriques
authors.forename: Paolo F
authors.initials: PF
authors.lastname: Maccarini
authors.forename: Paul R
authors.initials: PR
authors.lastname: Stauffer
authors.forename: Alireza
authors.initials: A
authors.lastname: Mashal
authors.forename: Mark W
authors.initials: MW
authors.lastname: Dewhirst
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D006979:Hyperthermia, Induced; D008297:Male; D008875:Middle Aged; D011507:Proteinuria; D013696:Temperature; D016482:Urinalysis; D001749:Urinary Bladder Neoplasms / Q000628:therapy; D014556:Urine / Q000737:chemistry*; D014783:Viscosity