Urinary osmolality in lithium and non-lithium treated psychiatric patients.

A study was conducted to determine the prevalence of urine concentrating defect in 57 psychiatric patients who were treated with lithium and 42 patients who were not treated with lithium. Analysis of results indicated that there was no statistically significant difference between the lithium treated and control groups in their random 12 hour fluid deprivation urine osmolality, 0.5 greater than p greater than 0.1, t-test. The authors suggest that impaired urinary concentrating ability occurs frequently in both lithium and nonlithium treated psychiatric patients. This isolated finding alone is insufficient to warrant the diagnosis of lithium nephrotoxicity.