Two unusual pediatric cases of dilutional hyponatremia.

Dilutional hyponatremia, although not uncommon, is an underestimated problem in the pediatric population. In most cases, it results from excessive hydration or water retention, also described as the so-called water intoxication. One of the most known causes is the use of desmopressin in enuretic children. This drug enhances the free water reabsorption in the renal collecting ducts. The addition of the anticholinergic agent oxybutynin aggravated the condition by causing a dry mouth with excessive thirst and water intake in our first case. Dietary water overconsumption, either voluntary or involuntary, is a phenomenon seen in formula-fed babies. But in our second case, a game involving forced ingestion of large amounts of water had serious consequences including hyponatremia-related coma. An effort should therefore be made to inform caretakers about the risks of these games. These cases, provoked by rather unusual and peculiar causes, illustrate again that electrolytes and especially serum [Na(+)] are key points to be determined in a child with diminished consciousness. Moreover, an accurate history including the intake of medication and dietary information should be made.