The effect of lithium on tubular functions leading to decreased urinary concentrating ability is recognized. Although there are several studies type, severity and frequency of renal impairment and its correlation with duration of lithium therapy are not well established.

To explore long-term effects of lithium on patients with chronic bipolar disorder.

We aimed to assess patients with bipolar disorder using lithium at least for six years in terms of renal functions, starting from mild impairments to full blown chronic renal failure.

Fifty-one patients with bipolar disorder and 38 age and sex matched healthy controls were enrolled for the study. Serum BUN, creatinine, uric acid, electrolytes, calcium (Ca), phosphorus (P), vitamin D (25-OH D3) and eGFR levels were measured. The correlations between renal function and mean lithium levels, duration of lithium treatment and GAF scores were calculated.

Mean eGFR level of patients with bipolar disorder was significantly lower than that of controls. Serum creatinine, uric acid, Ca and PTH levels were higher, 25-OH D3 levels were lower in the patients than in controls. The duration of lithium treatment was positively correlated with serum creatinine and uric acid levels, negatively correlated with eGFR levels. Mean lithium levels were positively correlated with serum creatinine levels and negatively correlated with eGFR.

The study revealed that glomerular functioning of the patient group was significantly lower than that of the control group. The findings suggested that both duration of lithium treatment and high serum lithium levels may have a negative impact on glomerular functions.

The authors have not supplied their declaration of competing interest.