A clinician's guide to monitoring kidney function in lithium-treated patients.

OBJECTIVE: Bipolar disorder treatment guidelines recommend kidney-function monitoring at regular intervals for patients taking lithium, but they tend not to provide specifics with regard to what to measure and how to ensure that the results most accurately reflect true kidney function. This overview clarifies those practical aspects of monitoring that are often overlooked or misunderstood. DATA SOURCES: Utilized English language materials were obtained by PubMed searches (1970-2009), from the Lithium Information Center database, and from books. Search terms included lithium, kidney function, creatinine, creatinine clearance, GFR, GFR prediction equations, albuminuria, and urine concentration. DATA SYNTHESIS: Urine osmolality most accurately reflects urine concentrating ability, although specific gravity is usually adequate for clinical purposes. Serum creatinine concentration can be influenced by extrarenal factors, but even when these are controlled, it remains a less than ideal measure of glomerular filtration rate (GFR). Prediction equations are used commonly to estimate GFR and are an advance over serum creatinine alone, but even they are not as useful when GFR is only mildly impaired. Urine albumin measurement is important, but it requires greater standardization and sensitivity to maximize its potential.
CONCLUSIONS: The safe and effective use of lithium requires regular monitoring of kidney function. Doing so effectively requires knowledge of what to measure, how to ensure accurate results, and how to properly interpret them. © Copyright 2010 Physicians Postgraduate Press, Inc.