Unrecognised Free Water Loss in a Patient with Lithium- Induced Nephrogenic Diabetes Insipidus Can Cause Acute Kidney Injury and Near Fatal Hypernatremia..

Acquired nephrogenic diabetes insipidus is most frequently caused by lithium which is used to treat bipolar disorder. The reported incidence of acquired NDI in patients on long term lithium treatment is as high as 55% [2]. Lithium-induced NDI results from inactivation of adenylyl cyclase and thus the phosphorylation of cytoplasmic urinary aquaporin 2 AQP2 by protein kinase A, and consequently ADH-induced translocation of cytoplasmic urinary aquaporin 2 (AQP2) to the apical membrane [3]. Lithium also down regulates the protein abundances of urea transporter, UTA1, UT-B, thus reducing medullary interstitial osmolality [4-6]. Lithium induced NDI should be suspected in any patient on longterm lithium therapy who develops unexplained hyper natremia so that prompt treatment can be instituted.