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Kidney Blood Press Res. 2019 Sep 10:1-12. doi: 10.1159/000502291. [Epub ahead of print]

Urine Osmolality and Renal Outcome in Patients with Chronic Kidney Disease: Results from the KNOW-CKD.

Author information

1
Department of Internal Medicine, CHA Bundang Medical Center, CHA University, College of Medicine, Seongnam, Republic of Korea.
2
Department of Internal Medicine, National Health Insurance Service Medical Center, Ilsan Hospital, Goyangshi, Republic of Korea.
3
Department of Prevention and Management, Inha University Hospital, Inha University School of Medicine, Incheon, Republic of Korea.
4
Department of Internal Medicine, Inje University, Pusan Paik Hospital, Busan, Republic of Korea.
5
Department of Internal Medicine, Seoul National University, Seoul, Republic of Korea.
6
Department of Internal Medicine, Nowon Eulji Medical Center, Eulji University, Seoul, Republic of Korea.
7
Department of Internal Medicine, Chonnam National University Medical School, Gwangju, Republic of Korea.
8
Department of Internal Medicine, College of Medicine, Institute of Kidney Disease Research, Yonsei University, Seoul, Republic of Korea.
9
Department of Internal Medicine, College of Medicine, Institute of Kidney Disease Research, Yonsei University, Seoul, Republic of Korea, hansh@yuhs.ac.

Abstract

BACKGROUND:

Urine osmolality indicates the ability of the kidney to concentrate the urine and reflects the antidiuretic action of vasopressin. However, results about the association between urine osmolality and adverse renal outcomes in chronic kidney disease (CKD) are conflicting. We investigated the association between urine osmolality and adverse renal outcomes in a nationwide prospective CKD cohort.

METHODS:

A total of 1,999 CKD patients were categorized into 3 groups according to their urine osmolality tertiles. Primary outcome was a composite of 50% decline in the estimated glomerular filtration rate (eGFR), initiation of dialysis, or kidney transplantation.

RESULTS:

During a mean follow-up of 35.2 ± 19.0 months, primary outcome occurred in 432 (21.6%) patients; 240 (36.4%), 162 (24.3%), and 30 (4.5%) in the lowest, middle, and highest tertiles, respectively. Low urine osmolality was independently associated with a greater risk of CKD progression (hazard ratio [HR], 1.71; 95% confidence interval [CI], 1.12-2.59). This association was particularly evident in patients with CKD stages 3-4 (per 10 mosm/kg decrease; HR, 1.02; 95% CI, 1.00-1.03). Adding urine osmolality to a base model with conventional factors significantly increased the ability to predict CKD progression (C-statistics, 0.86; integrated discrimination improvement [IDI], 0.021; both p < 0.001). However, adding both urine osmolality and eGFR did not further improve the predictive ability compared with the addition of eGFR only (C-statistics, p = 0.29; IDI, p = 0.09).

CONCLUSIONS:

Low urine osmolality was an independent risk factor for adverse renal outcomes in CKD patients, but its predictive ability did not surpass eGFR. Thus, kidney function should be considered while interpreting the clinical significance of urine osmolality.

KEYWORDS:

Chronic kidney disease; Estimated glomerular filtration rate; Outcome; Urine osmolality

PMID:
31505490
DOI:
10.1159/000502291
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