A218 A CASE REPORT OF PSEUDOHYPONATREMIA IN CHOLESTATIC LIVER DISEASE

Abstract Background True hyponatremia in the setting of cholestatic liver disease may signify cirrhosis with fluid overload, and is therefore an ominous sign of deteriorating liver function. In pediatric liver transplant candidates, it is associated with increased waitlist mortality. Pseudohyponatremia however, is a falsely low measurement of plasma sodium when measured by indirect potentiometry. Pseudohyponatremia secondary to hypercholesterolemia is a phenomenon that occurs due to a reduced aqueous fraction of the plasma when levels of cholesterol or triglycerides are greatly elevated. Severe hypercholesterolemia due to Lipoprotein X accumulation may be the cause of pseudohyponatremia in biliary obstruction or cholestasis. Aims To describe a case of pseudohyponatremia secondary to hypercholesterolemia in an infant with Alagille syndrome (ALGS) and cholestatic liver disease. Methods This 7 month-old male with ALGS (confirmed JAGGED1 mutation) and severe cholestasis, failure to thrive, and pruritus, developed new-onset progressive hyponatremia as low as 121 mmol/L at an outside institution. He was therefore transferred to our center for liver transplant assessment due to concerns of progressive liver dysfunction and for management of the hyponatremia. Results Upon admission, the patient was jaundiced but euvolemic, with no evidence of ascites or peripheral edema. Laboratory work drawn at our institution showed conjugated bilirubin of 180 mmol/L, ALT 300 U/L, AST 250 U/L, and GGT 1200 U/L. INR was 1.1 and albumin of 35 g/L. The cholesterol was elevated above 16.8 mmol/L, with high triglycerides 2.68 mmol/L, and the serum appeared visibly lipemic. The sodium level was 138 mmol/L as measured by direct potentiometry due to the visible lipemia. The osmolality of 288 mmol/kg was normal with a normal osmolar gap. Urine osmolality and sodium were also normal. He underwent routine evaluation and was listed for a liver transplant due to the profound cholestasis and growth failure. Conclusions Pseudohyponatremia is an important entity to recognize when caring for patients with cholestatic liver disease and hyponatremia. Both direct potentiometry and indirect potentiometry are currently used for sodium testing in blood in biochemistry laboratories. These measurement techniques show good agreement as long as protein and lipid concentrations in blood are normal, however, hyperlipidemia is a well-recognized cause for error in sodium estimation. It is therefore imperative to evaluate apparent hyponatremia correctly, especially when the patient appears euvolemic clinically and by normal serum osmolality. In this clinical setting, pseudohyponatremia is the likely cause and a workup should be carried out to identify possible underlying etiologies, the most probable being hypercholesterolemia. Failure to recognize this phenomenon may lead to unnecessary and potentially harmful treatments and interventions. Funding Agencies None

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