Low Sodium Excretion in SIADH Patients with Low Diuresis

Abstract

It is well known that during low diuresis or low effective circulating volume, salt excretion is low. The aim of this study was to find out whether salt excretion, expressed as either urinary sodium concentration (UNa) or fractional sodium excretion (FENa), and the combined use of FENa and fractional urea excretion (FEurea) still differentiate between hyponatremic SIADH and hyponatremic salt depletion (SD) patients when diuresis is low. The relationships between UNa, FENa and diuresis, indirectly estimated by the urinary to plasma creatinine ratio (U/P creat), were studied in 42 hyponatremic SIADH patients, 21 hyponatremic SD patients and 66 normonatremic controls (CO) of similar age and sex ratio. There was no significant relationship between UNa and U/P creat either in SIADH or in SD or CO patients. FENa and U/P creat were inversely correlated, both in CO (r = –0.72; p < 0.001) and in SIADH (r = –0.68; p < 0.001). SIADH and SD patients can be fairly well differentiated from one another using FENa and U/P creat. Even with high U/P creat values, SIADH patients, despite a sharp decrease in their FENa values, presented still higher FENa values than SD patients did (mean FENa = 0.3 ± 0.2% in SIADH and 0.1 ± 0.04% in SD; p < 0.05). However, FENa values of SIADH patients with low diuresis (mean FENa = 0.3 ± 0.2% for a mean U/P creat = 191 ± 40) are indistinguishable from those of SD patients with normal urine volumes (mean FENa = 0.2 ± 0.2% for a mean U/P creat = 92 ± 30). The combined use of FENa and FEurea remains a reliable way to discriminate SD patients and SIADH patients, as far as the differential limit value for FENa is narrowed to a value of 0.15%, for hyponatremic patients with U/P creat >140. Conclusion: In SIADH, FENa values are lower than 0.5%, as soon as U/P creat exceeds a value of 180. In SD patients with U/P creat values exceeding 140, FENa is lower than 0.15% and FEurea lower than 45%.

Journal

Journal ID (publisher-id): NEP

Journal ID (nlm-ta): Nephron Physiol

Journal ID (doi): 10.1159/issn.1660-2137

Title: Nephron Physiology

Publisher: S. Karger AG

ISSN (Electronic): 1660-2137

Publication date Subscription-year: 2004

Publication date (Print): January 2004

Publication date (Electronic): 02 February 2004

Volume: 96

Issue: 1

Pages: p11-p18

Affiliations

^aDepartment of Internal Medicine, Bracops Hospital, Brussels, and ^bResearch Unit for the Study of Hydromineral Metabolism, Erasme University Hospital, Free University of Brussels, Brussels, Belgium

Article

Publisher ID: 75575 Other ID: Nephron Physiol 2004;96:p11–p18

DOI: 10.1159/000075575

PubMed ID: 14752239

Copyright statement: © 2004 S. Karger AG, Basel

License:

Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher. Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug. Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.

Page count

Figures: 3, Tables: 1, References: 11, Pages: 1

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Categories

Subject: Original Paper