Renal function and biopsy in patients on lithium-therapy.

The renal function of 46 outpatients from a lithium-clinic was examined in detail during 5 days of hospitalization on a nephrological ward. Lithium medication was stopped seven days before admission. In approximately 25% of the examined patients, a lithium-induced nephropathia must be assumed. Irreversibility of the disturbances cannot be excluded. The characteristic feature of this patient population is to be seen in an exclusive reduction of the renal concentrating ability. Urine osmolality showed a significant negative correlation to the product of duration of treatment times lithium serum concentration. In all patients with a reduced GFR a preexisting kidney disease could be demonstrated. The degree of polyuria was not related to the observed impairment of renal function. On the average it took seven years until a reduced concentration ability became apparent; the minimal time interval was three years. The lithium-associated nephropathy may be characterized as a rather frequently occurring damage of the kidney interstitium being dependent on serum-lithium concentration and duration of treatment. Progress of these pathological changes is obviously very slow and accompanied by only few and mild clinical symptoms. Kidney biopsy in 4 cases revealed focal fibrosis and tubular degeneration as has been described by other authors.