MRI-based kidney radiomic analysis during chronic lithium treatment

Background: Lithium therapy during bipolar disorder is associated with an increased risk of chronic kidney disease (CKD) that is slowly progressive and undetectable at early stages. We aimed at identifying kidney image texture features as possible imaging biomarkers of decreased measured glomerular filtration rate (mGFR) using radiomics of T2-weighted magnetic resonance imaging (MRI). Methods: One hundred and eight patients treated with lithium were evaluated including mGFR and kidney MRI, with T2-weighted sequence single-shot fast spin-echo. Computed radiomic analysis was performed after kidney segmentation. Significant features were selected to build a radiomic signature using multivariable Cox analysis to detect an mGFR <60 ml/min/1.73 m². The texture index was validated using a training and a validation cohort. Results: Texture analysis index was able to detect an mGFR decrease, with an AUC of 0.85 in the training cohort and 0.71 in the validation cohort. Patients with a texture index below the median were older (59 [42–66] vs. 46 [34–54] years, p =.001), with longer treatment duration (10 [3–22] vs. 6 [2–10] years, p =.02) and a lower mGFR (66 [46–84] vs. 83 [71–94] ml/min/1.73m², p <.001). Texture analysis index was independently and negatively associated with age (β = −.004 ± 0.001, p <.001), serum vasopressin (−0.005 ± 0.002, p =.02) and lithium treatment duration (−0.01 ± 0.003, p =.001), with a significant interaction between lithium treatment duration and mGFR (p =.02). Conclusions: A renal texture index was developed among patients treated with lithium associated with a decreased mGFR. This index might be relevant in the diagnosis of lithium-induced renal toxicity.