title: Urinary Analysis of Fluid Retention in the General Population: A Cross-Sectional Study.
abstract: OBJECTIVE
  Renal conservation (retention) of fluid might affect the outcome of hospital care and can be indicated by increased urinary concentrations of metabolic waste products. We obtained a reference material for further studies by exploring the prevalence of fluid retention in a healthy population.
  
  
  METHODS
  Spot urine sampling was performed in 300 healthy hospital workers. A previously validated algorithm summarized the urine-specific gravity, osmolality, creatinine, and color to a fluid retention index (FRI), where 4.0 is the cut-off for fluid retention consistent with dehydration. In 50 of the volunteers, we also studied the relationships between FRI, plasma osmolality, and water-retaining hormones.
  
  
  RESULTS
  The cut-off for fluid retention (FRI ≥ 4.0) was reached by 38% of the population. No correlation was found between the FRI and the time of the day of urine sample collection, and the FRI was only marginally correlated with the time period spent without fluid intake. Volunteers with fluid retention were younger, generally men, and more often had albuminuria (88% vs. 34%, P < 0.001). Plasma osmolality and plasma sodium were somewhat higher in those with a high FRI (mean 294.8 vs. 293.4 mosmol/kg and 140.3 vs. 139.9 mmol/l). Plasma vasopressin was consistently below the limit of detection, and the plasma cortisol, aldosterone, and renin concentrations were similar in subjects with a high or low FRI. The very highest FRI values (≥ 5.0, N = 61) were always accompanied by albuminuria.
  
  
  CONCLUSIONS
  Fluid retention consistent with moderate dehydration is common in healthy staff working in a Swedish hospital.
authors.affiliation: Research Unit, Södertälje Hospital, 152 86, Södertälje, Sweden.
authors.forename: Robert G
authors.identifier: http://orcid.org/0000-0002-1528-3803
authors.initials: RG
authors.lastname: Hahn
authors.affiliation: Research Unit, Södertälje Hospital, 152 86, Södertälje, Sweden.
authors.forename: Nina
authors.initials: N
authors.lastname: Grankvist
authors.affiliation: Research Unit, Södertälje Hospital, 152 86, Södertälje, Sweden.
authors.forename: Camilla
authors.initials: C
authors.lastname: Krizhanovskii
mesh_terms: D000328:Adult; D000419:Albuminuria / Q000473:pathology; D000450:Aldosterone / Q000097:blood; D001826:Body Fluids / Q000737:chemistry* / Q000378:metabolism; D003404:Creatinine / Q000652:urine; D003430:Cross-Sectional Studies; D003681:Dehydration / Q000652:urine*; D005260:Female; D006282:Health Personnel / Q000706:statistics & numerical data; D006801:Humans; D006854:Hydrocortisone / Q000097:blood; D008297:Male; D015999:Multivariate Analysis; D009994:Osmolar Concentration; D012083:Renin / Q000097:blood; D013046:Specific Gravity; D016482:Urinalysis; D014667:Vasopressins / Q000097:blood
chemical_list: D014667:Vasopressins; D000450:Aldosterone; D003404:Creatinine; D012083:Renin; D006854:Hydrocortisone