Which of the following is a common cause of pseudohyponatremia?

Pseudohyponatremia occurs when the sodium concentration in the blood appears lower than it actually is, typically due to the presence of other substances in the serum, such as lipids or proteins that can affect the measurement of sodium. Hyperlipidemia is a well-known cause of pseudohyponatremia because the high levels of lipids in the blood can interfere with the laboratory methods used to measure sodium concentration, leading to an inaccurately low sodium reading. In cases of hyperlipidemia, the water content of the plasma becomes diluted in relation to the lipids, resulting in a lower apparent sodium concentration even though the actual sodium level remains normal.

Other conditions, such as acute renal failure, diabetes insipidus, and heart failure, do not typically cause pseudohyponatremia but can lead to true hyponatremia due to various physiological mechanisms, such as altered fluid balance or hormone regulation. Understanding the factors that contribute to pseudohyponatremia is essential for accurate diagnosis and treatment, emphasizing the importance of considering potential interferences in laboratory results.