The aim of the study was to detect early markers of nephrotoxicity lithium-induced by blood test and ultrasound and magnetic resonance imaging (MRI). The nephrotoxicity effects of lithium are characterized by reduced urinary concentrating capacity wich can be detected as early as 8 weeks after lithium initiation. Nephrogenic diabetes insipidus is the most common adverse effect and occurs in up to 40% of patients.
To test the hypothesis, we enrolled twenty-six patients treated with lithium for more than one year and with one of the following symptoms or findings: polyuria-polydipsia, urine specific gravity < 1005, GFR < 90 ml/min/1.73 mq, proteinuria, hypertension. Patients underwent blood tests, urine NGAL, renal Doppler ultrasound and MRI in the presence of cysts.
Of the twenty-six patients enrolled in the study ten had cysts and five had microcystic type cysts, pathognomonic of chronic tubulointerstitial nephritis. All patients with renal microcysts had a renal resistance index (RI) > 0.65. There were no correlations with NGAL.
According to data of IR index it is advisable to perform a renal Doppler ultrasound screening for patients treated with lithium as monitoring of renal function using only blood tests and urinary NGAL is insufficient. The practice guidelines of the American Psychiatric Association recommend measurement of serum creatinine level every 2-3 months during the first six months of lithium therapy and every year thereafter. The decision to substitute lithium with another mood stabilizer raises a dilemma and should be made jointly by the patient, the psychiatrist and the nephrologist. The issue is debated because the beneficial renal effect of lithium discontinuation might be observed, and not always, only in patients with moderate nephropathy. Maybe a point of no return exist, after which renal fibrosis continues to progress despite removal of the triggering insult.