Structural and functional effects of long-term lithium therapy.

To determine the effects of long-term lithium therapy, we have studied the renal histology and the renal function of 47 patients with affective disorders who were either currently receiving or had previously received maintenance lithium therapy (lithium patients), and we have compared the results with those of 32 other psychiatric patients with similar affective illnesses who had never taken lithium (prelithium patients). The renal biopsy samples, analyzed by a point-counting technique for interstitial fibrosis, were not different in degree between the lithium and the prelithium patients. Interstitial fibrosis was also not different between prelithium patients and age-matched transplant donor kidney controls, but it was greater in lithium patients when compared with the donor kidney controls (P less than 0.01). The specific distal tubular lesion associated with lithium therapy was present in all the biopsy samples of the patients who were currently receiving lithium therapy. Marked distal nephron dysfunction, as measured by urinary concentrating ability (P less than 0.0001) and urinary acidification (P less than 0.0001), was evident in lithium patients compared with the prelithium patients. These defects were correlated with the duration of lithium therapy. Serum creatinine estimations (P less than 0.01), serum beta-2 microglobulins (P less than 0.01), and 51Cr-EDTA clearances (P less than 0.01) suggested some impairment of GFR in lithium patients compared with prelithium patients. These defects did not correlate with the duration of lithium therapy. From these studies we concluded that the marked distal nephron dysfunction induced by lithium might produce prerenal impairment of GFR because the renal function abnormalities have no structural basis when the degree of interstitial fibrosis of other psychiatric patients is used as a control. Prospective studies are needed to answer the controversial question of whether stable maintenance lithium therapy produces chronic nephrotoxicity.