Is urinary density an adequate predictor of urinary osmolality?

BMC Nephrology

Research Article

Mirela A R Santinho¹  João E Romão¹  Roberto Zatz¹  Marcia Ribalta¹  Rosilene M Elias¹  Ana Carolina P Souza¹  Rodrigo B de Oliveira² 

[1] Nephrology Service, University of Sao Paulo School of Medicine, São Paulo, SP, Brazil;Nephrology Service, University of Sao Paulo School of Medicine, São Paulo, SP, Brazil;Nephrology Service, University of Campinas - UNICAMP, Campinas, Brazil;

关键词: Kidney disease;    Urinalysis;    Urine density;    Urine osmolality;    Urine concentrating ability;   

DOI  :  10.1186/s12882-015-0038-0

 received in 2014-08-12, accepted in 2015-03-24,  发布年份 2015

来源: Springer

【 摘 要 】

BackgroundUrinary density (UD) has been routinely used for decades as a surrogate marker for urine osmolality (Uosm). We asked if UD can accurately estimate Uosm both in healthy subjects and in different clinical scenarios of kidney disease.MethodsUD was assessed by refractometry. Uosm was measured by freezing point depression in spot urines obtained from healthy volunteers (N = 97) and in 319 inpatients with acute kidney injury (N = 95), primary glomerulophaties (N = 118) or chronic kidney disease (N = 106).ResultsUD and Uosm correlated in all groups (p < 0.05). However, a wide range of Uosm values was associated with each UD value. When UD was ≤ 1.010, 28.4% of samples had Uosm above 350 mOsm/kg. Conversely, in 61.6% of samples with UD above 1.020, Uosm was below 600 mOsm/kg. As expected, Uosm exhibited a strong relationship with serum creatinine (Screat), whereas a much weaker correlation was found between UD and Screat.ConclusionWe found that UD is not a substitute for Uosm. Although UD was significantly correlated with Uosm, the wide dispersion makes it impossible to use UD as a dependable clinical estimate of Uosm. Evaluation of the renal concentrating ability should be based on direct determination of Uosm.

【 授权许可】

Unknown   
© Souza et al.; licensee BioMed Central. 2015. This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.