I am a Registered Dietitian who works at a state hospital, and many of the older patients who have been on Lithium for long periods have developed nephrogenic diabetes insipidus. What is the appropriate diet to help preserve kidney function? I have always heard that a protein restriction and a sodium restriction is indicated. Is this true? What about potassium and phosphorus?

The biggest issue is to make sure the patients have unlimited access to free water. The Diabetes Insipidus is nephrogenic so that it is potentially amenable to amiloride. These patients develop hypernatremia so that their sodium levels may be elevated. However, they are not total body sodium overloaded. They are free water depleted. When patients have DI for a long period of time, the DI can be irreversible, even if the lithium is stopped. Protein and phosphorus restriction is important when creatinine clearance is severely declined.

JTL

[Editor’s comment: Diabetes insipidus is a different disorder than diabetes mellitus.

WWQ]