RESUMEN
OBJECTIVE: The aim of this study was to investigate the effect of lithium treatment on renal function and to determine influencing factors. In addition, the utility of spot urine protein/creatinine ratio in detection of lithium induced nephropathy was also investigated. METHODS: Serum concentrations of lithium, blood urea nitrogen (BUN), creatinine, estimated glomerular filtration rate (eGFR), and urinalysis including protein/creatinine ratio were measured in 375 patients using lithium. RESULTS: Patients taking lithium for ≥8 years had higher BUN, creatinine levels, percentage of proteinuria, percentages of stage 2 and 3 chronic kidney disease (CKD); lower urine density and eGFR compared to patients taking lithium <8 years. Urine density was lower in groups with >0.8 and 0.6-0.8 mmol/L lithium level than <0.6 mmol/L. Predictors of CKD were serum level of lithium, dose of lithium, cumulative duration of lithium use, age at onset of illness, and caffeine consumption. CONCLUSIONS: Detrimental effects of lithium on renal functions were detected after lithium use for ≥8 years. Proteinuria measured by spot urine protein/creatinine ratio can be detected even when eGFR is >90 ml/min/1.73 m2 . Spot urine protein/creatinine ratio, which is a cost-effective and practical laboratory test, can be used to monitor lithium-treated patients.