title: Glomerular filtration rate estimated by 3-sample plasma clearance of iohexol in 118 healthy dogs.
abstract: BACKGROUND
  Glomerular filtration rate (GFR) decreases in the aging human kidney, but limited data exist in dogs.
  
  
  OBJECTIVE
  There is an effect of age and body size on estimated GFR in healthy dogs.
  
  
  METHODS
  One hundred and eighteen healthy dogs of various breeds, ages, and body weights presenting to 3 referral centers.
  
  
  METHODS
  GFR was estimated in clinically healthy dogs between 1 and 14 years of age. GFR was estimated from the plasma clearance of iohexol, by a compartmental model and an empirical correction formula, normalized to body weight in kilograms or liters of extracellular fluid volume (ECFV). For data analysis, dogs were divided into body weight quartiles 1.8-12.4, 13.2-25.5, 25.7-31.6, and 32.0-70.3 kg.
  
  
  RESULTS
  In the complete data set, there was no trend toward lower estimated GFR/kg or GFR/ECFV with increasing age. GFR decreased with age in dogs in the smallest weight quartile only. A significant negative linear relationship was detected between body weight and estimated GFR/kg and GFR/ECFV. Reference ranges in different weight quartiles were 1.54-4.25, 1.29-3.50, 0.95-3.36, and 1.12-3.39 mL/min/kg, respectively. Standardization to ECFV rather than kilogram body weight did not produce substantial changes in the relationships between GFR estimates and age or weight.
  
  
  CONCLUSIONS
  Interpretation of GFR results for early diagnosis of renal failure should take into account the weight and the age of the patient for small dogs.
authors.affiliation: Department of Veterinary Medicine, University of Cambridge, Cambridge, UK. nb289@cam.ac.uk
authors.forename: N H
authors.initials: NH
authors.lastname: Bexfield
authors.forename: R
authors.initials: R
authors.lastname: Heiene
authors.forename: R J
authors.initials: RJ
authors.lastname: Gerritsen
authors.forename: U
authors.initials: U
authors.lastname: Risøen
authors.forename: K A
authors.initials: KA
authors.lastname: Eliassen
authors.forename: M E
authors.initials: ME
authors.lastname: Herrtage
authors.forename: A R
authors.initials: AR
authors.lastname: Michell
mesh_terms: D000375:Aging; D000818:Animals; D001835:Body Weight; D003287:Contrast Media / Q000493:pharmacokinetics*; D004285:Dogs / Q000097:blood / Q000378:metabolism*; D005919:Glomerular Filtration Rate / Q000502:physiology / Q000662:veterinary*; D007472:Iohexol / Q000493:pharmacokinetics*; D007668:Kidney / Q000378:metabolism
chemical_list: D003287:Contrast Media; D007472:Iohexol