A renal function study in 30 patients on long-term lithium therapy

30 patients on long-term lithium therapy have been studied. The results are presented of the urinary concentrating ability after water deprivation and the intranasal administration of vasopressin, of the simultaneous determination of glomerular filtration rate (GFR) and effective renal plasma flow (ERPF), of the minimal urine pH after an oral dose of ammonium chloride, and of the urinary beta-2-microglobulin excretion. Mean urine concentration (+/- SEM) after 22 hr water deprivation (= Uosm) amounted to 854 +/- 22 mOsm/kg H2O, mean GFR was 101 +/- 4 ml/min, mean ERPF 360 +/- 18 ml/min, and mean minimal urine pH 4.95 +/- 0.06. In 8 out of 30 patients there was polyuria. In these 8 patients the values were 778 +/- 51 mOsm/kg H2O, 113 +/- 6 ml/min, 415 +/- 33 ml/min and 4.99 +/- 0.08, respectively. Serum levels of beta-2-microglobulin and lysozyme and the urinary excretion of beta-2-microglobulin were normal in all patients. No correlation was established between Uosm and the serum lithium concentration during the test (0.8 +/- 0.05 mmoles/l) nor between Uosm and the average serum lithium level during treatment (0.79 +/- 0.03). GFR was only correlated with age. It was found that administration of indomethacin during the concentration test increased Uosm in these patients. The results suggest that, given proper dosage and surveillance, long-term treatment with lithium is not likely to cause disturbances in renal function.