MR imaging as a specific diagnostic tool for bilateral microcysts in chronic lithium nephropathy.

A 59-year-old man was referred by his family doctor for progressive renal failure. He was on lithium sulfate therapy since 32 years for bipolar disorder. The medical history revealed polyuria and polydypsia, which was persistent since several years. Family history was negative for hereditary nephropathies. Laboratory findings revealed a blood urea nitrogen concentration of 7.0 mmol/l and a serum creatinine concentration of 168 mmol/l, corresponding to an estimated glomerular filtration rate of 38 ml/min per 1.73 m according to the Modification of Diet in Renal Disease formula. There was no electrolyte anomaly. Urinalysis demonstrated a pH of 7.0, and a specific gravity of 1005, without protenuria nor hematuria. A chronic lithium nephropathy (CLN) was suspected and a renal biopsy proposed, but was refused by the patient. Long-term lithium administration may cause a progressive nonreversible defect in urinary concentrating ability due to CLN, which can progress to end-stage renal disease (ESRD). Time on lithium therapy and susceptibility to the nephrotoxic effects of lithium are the only known risk factors for CLN and ESRD. Renal biopsy findings of CLN include nonspecific chronic tubulointerstitial changes, except for cortical and medullar tubular dilation and microcysts, which are observed in the majority of patients. Magnetic resonance (MR) imaging, in particular the halfFourier acquisition single-shot turbo spin-echo T2-weighted sequence, without the use of gadolinium, is the best noninvasive method to demonstrate the presence of renal microcyts of a diameter of 1–2 mm. In our patient, MR imaging showed two hyperechogenic normal-size kidneys, filled with multiple corticomedullary microcysts (Figure 1). Typical MR imaging of microcysts, in a patient with chronic renal failure appearing after long-term lithium therapy, allows confirmation of the clinical diagnosis of CLN, without performing a renal biopsy. Lithium therapy was subsequently replaced in our patient. http://www.kidney-international.org n e p h r o l o g y i m a g e