Background. Lithium is the most effective drug for mood stabilization in bipolar disorder. However, lithium exposure has been associated with an impaired renal
concentrating ability (RCA) and glomerular filtration rate (GFR). We examined RCA and estimated GFR in a cohort of patients treated with lithium.
Methods. 134 patients (≥ 18 years of age) with a mood disorder treated with lithium were screened; 100 patients were included. Demographic and clinical characteristics and blood and urine samples were collected. Additionally, a dDAVP-test was performed to determine maximal RCA.
Results. A dDAVP-test was performed in 98 patients (37 males, 61 females). Mean age was 51 years (SD: 12), median duration of lithium therapy 7 years (IQR: 4-15), mean maximal urine osmolality (Uosmol) 725 mOsmol/kg (SD: 153), and median eGFR 84 ml/min/1.73 m2 (IQR: 68-95). Fifty patients (51%) had an impaired RCA and 17 patients (17%) had nephrogenic diabetes insipidus (Uosmol 600-800 and < 600 mOsmol/kg, respectively). Notably, clinical symptoms did not predict an impaired RCA. Nineteen patients (19%) had an eGFR ≤ 60 ml/min/ 1.73 m2. Multivariable regression analysis showed a significant association between the duration of lithium treatment and maximal Uosmol (B = -6.1, 95%-CI: -9.4, -2.9, p < 0.001) and eGFR (B = -0.6, 95%-CI: 0.2, -3.3; p < 0.01).
Conclusions. RCA is impaired in the majority of lithium-treated patients. Both RCA and eGFR are inversely associated with the duration of lithium therapy. Prospective follow-up will enable us to evaluate if abnormalities in RCA can be used to predict the development of lithium-induced chronic kidney disease.