Determinants of Kidney Function and Accuracy of Kidney Microcysts Detection in Patients Treated With Lithium Salts for Bipolar Disorder.

Early kidney damage during lithium treatment in bipolar disorder is still hypothetical. We aimed at identifying the determinants of a decreased measured glomerular filtration rate (mGFR) and the accuracy of kidney MRI imaging in its detection. In this cross-sectional cohort study, 217 consecutive lithium-treated patients underwent mGFR and kidney MRI with half-Fourier turbo spin-echo and Single-shot with long echo time sequences. Median age was 51 [27-62] years, and median lithium treatment duration was 5 [2-14] years. 52% of patients had a stage 2 CKD. In multivariable analysis, the determinants of a lower mGFR were a longer lithium treatment duration (β -0.8 [-1; -0.6] ml/min/1.73 m GFR decrease for each year of treatment), a higher age (β -0.4 [-0.6; -0.3] ml/min/1.73 m for each year of age, < 0.001), albuminuria (β -3.97 [-6.6; -1.3], = 0.003), hypertension (β -6.85 [-12.6; -1.1], = 0.02) and hypothyroidism (β -7.1 [-11.7; -2.5], = 0.003). Serum lithium concentration was not associated with mGFR. Renal MRI displayed renal microcyst(s) in 51% of patients, detected as early as 1 year after lithium treatment initiation. mGFR and lithium treatment duration were strongly correlated in patients with microcyst(s) (r = -0.64, < 0.001), but not in patients with no microcysts (r = -0.24, = 0.09). The presence of microcysts was associated with the detection of an mGFR <45 ml/min/1.73 m (AUC 0.893, < 0.001, sensitivity 80%, specificity 81% for a cut-off value of five microcysts). Lithium treatment duration and hypothyroidism strongly impacted mGFR independently of age, especially in patients with microcysts. MRI might help detect early lithium-induced kidney damage and inform preventive strategies.