Abstract: TH-PO329
X Marks the Salt: A Case of Pseudohyponatremia Due to Lipoprotein X
Session Information
- Sodium, Potassium, and Volume Disorders: Clinical
October 24, 2024 | Location: Exhibit Hall, Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Fluid, Electrolytes, and Acid-Base Disorders
- 1102 Fluid, Electrolyte, and Acid-Base Disorders: Clinical
Authors
- Calder, Madison B., The University of Texas Health Science Center at San Antonio, San Antonio, Texas, United States
- Duch, John M., Audie L Murphy Memorial Veterans' Hospital, San Antonio, Texas, United States
Introduction
Pseudohyponatremia is a lab artifact produced when indirect ion-selective electrode (I-ISE) laboratory instruments, which incorporate a pre-measurement dilution step, measure serum sodium in the presence of abnormally increased non-aqueous components (e.g., protein/lipid). Instruments utilizing direct ion-selective electrode (D-ISE) technology are not affected; a marked discrepancy in serum sodium concentrations obtained with I-ISE and D-ISE instruments can be revealing. We present a case of pseudohyponatremia due to lipoprotein X (Lp-X).
Case Description
A 34-year-old man was admitted to the hospital with jaundice and abdominal pain. Examination was notable for normal mentation, scleral icterus, and hepatomegaly. Abdominal ultrasonography demonstrated severe hepatic steatosis. Initial laboratory studies performed using an I-ISE autoanalyzer were notable for severe hyponatremia, mild hyperglycemia, hyperbilirubinemia, and elevated ethanol level. Further diagnostic workup revealed significantly elevated lipids and a sodium value within normal limits obtained using a D-ISE analyzer. Subsequent agarose gel lipid pheresis suggested markedly elevated Lp-X. His clinical status and lab values improved with supportive care, nearly normalizing by six months after ethanol cessation (Table 1).
Discussion
Lp-X is an abnormal lipoprotein rich in unesterified cholesterol and phospholipids with similar density to low density lipoprotein molecules. Obstructive cholestasis causes reflux of lipid fractions from bile into plasma and can lead to serum Lp-X elevations. Treatment involves reversing the cholestatic liver disease. Importantly, our patient’s triglyceride level of 1252 mg/dL would only be expected to lower his serum sodium by approximately 2 mEq/L using proposed estimating equations, much less than was observed. Until Lp-X levels normalize, accurate serum sodium determination requires direct potentiometry analysis. Failure to promptly recognize pseudohyponatremia can lead to inappropriate therapy with disastrous consequences.