SHM Converge Scientific Abstract ePoster Gallery-Pseudohyponatremia in the Presence of Obstructive Jaundice

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This case report describes pseudohyponatremia in a 59-year-old woman with painless jaundice, transaminitis, and a recently discovered perihilar lung mass with liver lesions. She initially presented with low measured sodium (129) and borderline hyponatremia studies, leading clinicians to suspect SIADH related to lung cancer. However, sodium remained unchanged after a fluid challenge, and biopsy ultimately showed non-small cell carcinoma rather than the small cell cancer typically associated with SIADH.<br /><br />Further evaluation revealed normal/isotonic serum osmolality, no monoclonal gammopathy, and a markedly abnormal lipid profile with very high total cholesterol and LDL. These findings suggested lipoprotein-X accumulation caused by biliary obstruction, producing pseudohyponatremia rather than true hyponatremia. ERCP confirmed distal common bile duct stricture with proximal and mid duct dilation; a biliary stent was placed, and the patient was discharged. Her sodium normalized on follow-up.<br /><br />The report explains that pseudohyponatremia occurs when sodium appears falsely low in laboratory testing despite normal in vivo sodium and normal serum osmolality, often due to excess lipids or proteins in the blood. In obstructive jaundice or cholestasis, lipoprotein-X can cause extreme hypercholesterolemia and misleading sodium results. Recognizing this mechanism is important because management should focus on treating the underlying biliary obstruction, not on unnecessary hyponatremia treatments.<br /><br />The authors also highlight cognitive bias, especially anchoring bias, where an early assumption—such as SIADH from suspected lung cancer—can distract clinicians from reconsidering the diagnosis when new data emerge.

Asset Subtitle

Ankita C. Yelamanchili

Meta Tag

Author List Ankita C. Yelamanchili, Bruno Alvarez Concejo, Merelyn Thomas

Category Clinical Vignettes

Concept Pseudohyponatremia

Concept True Hyponatremia

Concept Serum Osmolality

Concept Sample Processing

Concept Obstructive jaundice

Distinguished Non-Finalist

Presenter Organization LSU Health Shreveport

Presenting Author Ankita C. Yelamanchili

Track Adult

Keywords

pseudohyponatremia

obstructive jaundice

lipoprotein-X

hyponatremia

SIADH

non-small cell carcinoma

biliary obstruction

hypercholesterolemia

anchoring bias

ERCP

Pseudohyponatremia

True Hyponatremia

Serum Osmolality

Sample Processing

Obstructive jaundice