Abstract
Objectives
Clinical and laboratory data of reset osmostat (RO) and cerebral/renal salt wasting (C/RSW) mimic syndrome of inappropriate antidiuretic hormone (SIADH) and can pose diagnostic challenges because of significant overlapping between clinical and laboratory findings. Failure to correctly diagnose hyponatremia may result in increased mortality risk, longer hospital stay, and is cost-effective. We aim to illustrate clinical and laboratory similarities and difference among patients with hyponatremic disorders and discuss the diagnostic value of factional uprate excretion (FEurate) to differentiate SIADH from RO and C/RSW.
Case presentations
We report the use of FEurate in the evaluation of three patients with hyponatremia and elevated urine osmolality in the absence of edema or clinical evidence of dehydration to differentiate SIADH from RO and C/RSW.
Conclusions
Measurement of FEurate may offset in part the diagnostic confusion imparted by the diagnoses of SIADH, RO, and C/RSW.
Research funding: None declared.
Author contributions: All authors contributed equally in the study design; in the collection, analysis, and interpretation of data; in the writing of the report; or in the decision to submit the report for publication.
Competing interests: The authors declare that they have no relevant financial interests.
Ethical standard: The manuscript does not contain experimental or interventional study.
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