title: Urine volume and change in estimated GFR in a community-based cohort study.
abstract: OBJECTIVE
  The effect of increased fluid intake on kidney function is unclear. This study evaluates the relationship between urine volume and renal decline over 6 years in a large community-based cohort.
  
  
  METHODS
  This prospective cohort study was undertaken in Canada from 2002 to 2008. We obtained 24-hour urine samples from adult participants with an estimated GFR (eGFR) ≥60 ml/min per 1.73 m(2) at study entry. Percentage annual change in eGFR from baseline was categorized as average decline <1% per year, between 1% and 4.9% (mild-to-moderate decline) or ≥5% (rapid decline).
  
  
  RESULTS
  2148 participants provided valid 24-hour urine samples, grouped as <1 L/d (14.5%); 1 to 1.9 L/d (51.5%); 2 to 2.9 L/d (26.3%); and ≥3 L/d (7.7%). Baseline eGFR for each category of urine volume was 90, 88, 84, and 87 ml/min per 1.73 m(2), respectively. Overall, eGFR declined by 1% per year, with 10% demonstrating rapid decline and 40% demonstrating mild-to-moderate decline. An inverse, graded relationship was evident between urine volume and eGFR decline: For each increasing category of 24-hour urine volume, percentage annual eGFR decline was progressively slower, from 1.3%, 1.0%, 0.8%, to 0.5%, respectively; P = 0.02. Compared with those with urine volume 1 to 1.9 L/d, those with urine volume ≥3 L/d were significantly less likely to demonstrate mild-to-moderate decline (adjusted odds ratio 0.66; 95% confidence interval 0.46 to 0.94) or rapid decline (adjusted odds ratio 0.46; 95% confidence interval 0.23 to 0.92); adjusted for age, gender, baseline eGFR, medication use for hypertension (including diuretics), proteinuria, diabetes, and cardiovascular disease.
  
  
  CONCLUSIONS
  In this community-based cohort, decline in kidney function was significantly slower in those with higher versus lower urine volume.
authors: Division of Nephrology, Department of Medicine, London Health Sciences Centre, London, Ontario, Canada. William.Clark@lhsc.on.ca
authors: William F
authors: WF
authors: Clark
authors: Jessica M
authors: JM
authors: Sontrop
authors: Jennifer J
authors: JJ
authors: Macnab
authors: Rita S
authors: RS
authors: Suri
authors: Louise
authors: L
authors: Moist
authors: Marina
authors: M
authors: Salvadori
authors: Amit X
authors: AX
authors: Garg
mesh_terms: D000328:Adult; D000368:Aged; D002170:Canada / Q000453:epidemiology; D016009:Chi-Square Distribution; D018450:Disease Progression; D004326:Drinking; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007668:Kidney / Q000503:physiopathology*; D007674:Kidney Diseases / Q000453:epidemiology / Q000503:physiopathology* / Q000517:prevention & control; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D011446:Prospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D013997:Time Factors; D014554:Urination