Hyponatremia, a Constant Clinical Challenge: Euvolemic Hyponatremia Secondary to Solute Loss

A 42-year-old female male with deceased donor kidney transplantation presented with a month old history of diarrhea and serum sodium of 116 meq/L. Her weight had been unchanged over the past 6 months. Patient had maintained adequate hydration of 2-3 liters per day despite diarrhea as per previous instructions.On presentation, she was euvolemic and non-orthostatic and rest of the examination was unremarkable. The SIADH which was initially suspected was ruled out due to remarkably low urine osmolality (62 mOsm/ Kg). She had no history of alcoholism, malnutrition, or psychogenic polydipsia. A diagnosis of euvolemic hyponatremia was made and cause was attributed to solute depletion from chronic diarrhea while she maintained liberal free water intake. Serum sodium normalized with intravenous normal saline followed by high salt diet. The case highlights that patients with diarrhea may present with euvolemic hyponatremia instead of hypovolemic hyponatremia if adequate oral free water intake is maintained.