Last reviewed: 23 Jun 2024
Last updated: 13 Jan 2021
Summary
Definition
History and exam
Key diagnostic factors
- presence of risk factors
- absence of hypovolaemia
- absence of hypervolaemia
- absence of signs of adrenal insufficiency or hypothyroidism
- nausea
- vomiting
- altered mental status
- headache
- seizure
- coma
Full details
Other diagnostic factors
- no history of recent diuretic use
Full details
Risk factors
- age >50 years
- pulmonary conditions (e.g., pneumonia)
- nursing home residence
- postoperative state
- malignancy
- medicine associated with SIADH induction
- central nervous system (CNS) disorder
- endurance exercise
Full details
Diagnostic investigations
1st investigations to order
- serum sodium
- serum osmolality
- serum urea
- urine osmolality
- urine sodium
Full details
Investigations to consider
- diagnostic trial with normal saline infusion
- serum uric acid
- fractional excretion of sodium
- fractional excretion of urea
- serum TSH
- serum cortisol level
- serum arginine vasopressin (AVP)
Full details
Treatment algorithm
ACUTE
severe symptoms
mild to moderate symptoms
asymptomatic with sodium ≥125 mmol/L (≥125 mEq/L)
ONGOING
persistence of chronic SIADH
Contributors
Authors
Megan Dixon, MD
Nephrologist
Arizona Kidney Disease and Hypertension Center
Phoenix
AZ
Disclosures
MD declares that she has no competing interests.
Howard Lien, MD, PhD
Professor Emeritus of Medicine
Division of Nephrology
University of Arizona
Tucson
AZ
Disclosures
HL is an author of a reference cited in this topic.
Peer reviewers
Judith H. Veis, MD
Associate Director
Nephrology
Washington Hospital Center
Washington
DC
Disclosures
JHV declares that she has no competing interests.
Laurie Solomon, MD, FRCP
Consultant Nephrologist
Renal Unit
Lancashire Teaching Hospitals
Fulwood
Preston
UK
Disclosures
LS declares that he has no competing interests.
Differentials
- Pseudohyponatraemia
- Hypovolaemia
- Cerebral salt-wasting
More DifferentialsGuidelines
- Society for endocrinology endocrine emergency guidance: Emergency management of severe symptomatic hyponatraemia in adult patients
- Clinical practice guideline on diagnosis and treatment of hyponatraemia
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