Summary
In patients with insufficient renal function and laboratory evidence of chronic tubulointerstitial nephritis (CTIN) associated to long-term lithium therapy, magnetic resonance imaging (MRI) has been shown to accurately detect the presence of specific renal microcysts, thus allowing confirmation of the clinical diagnosis.
Objective
We hypothesized that the development of morphological damage evidenced by MRI would precede the impairment of renal functional indices, mainly glomerular filtration rate (GFR).
Method
To test the hypothesis, we examined 3 consecutive patients treated with lithium for more than a decade and with no signs of renal disease. The patients were specifically selected for showing estimated GFR (eGFR) close to the normal threshold of 60 mL/min/1.73 m2.
Results
Two out of these 3 patients displayed 5-10 renal microcysts measuring from 1 to 2 mm in diameter in each kidney. The patients were a 53 y.o. female and a 48 y.o. male on lithium therapy for 17 and 22 years and with an eGFR of 67 and 63 mL/min/1.73 m2, respectively (Table I). Neither patient presented with factors considered to be related to the development of tardive nephropathy, e.g., past episodes of lithium intoxication or elevated serum lithium levels.
Conclusion
These 2 cases suggest that, in patients on long-term lithium therapy and with eGFR values close to normal limits, MRI may unveil structural renal pathology typical to CTIN in the absence of other signs of disease. Should the findings be substantiated by further observations, MRI may be used to screen for lithium-induced tardive nephropathy in patients at risk (Fig. 1).