We had a super interesting case presented this morning by Vivan Tran!
Diabetes Insipidus is diagnosed by a water deprivation test.
- There should be little increase in urine osms over time if the patient has DI.
- After administration of desmopressin, the urine osms increase dramatically in central DI, and stay low in nephrogenic DI.
Treatment of Central DI consists of low-solute diet, thiazides/NSAIDs, and most patients need desmopressin
- Thiazide diuretics can induce a mild hypovolemic state. The nephron compensates and increases the water and sodium reabsorption in the loop of Henle (proximal to where ADH works in the collecting duct). Therefore the urine would be more concentrated, decreasing the amount of polyuria, even though ADH is not present or working.
*Patients suspected of having nephrogenic DI (long term Lithium use) should not have a water deprivation test because of the risk of volume depletion and hypernatremia. Also it is recommended in all patients to avoid overnight water deprivation for the same reason.