Use of the osmolal gap in diagnosing mixed physiology hyponatremia in a child with B-cell acute lymphoblastic leukemia.

Hyponatremia is common among children undergoing treatment for hematologic malignancies and may be attributed to multiple underlying causes. In cases of hyponatremia due to mixed physiology, the osmolal gap, can identify pseudohyponatremia that may be masked by other causes.