Lithium-induced focal interstitial fibrosis in the rat kidney.

An early stage of focal cortical interstitial fibrosis and nephronic atrophy was found by light microscopy in the kidneys of nine out of twelve rats which had received lithium for 9 weeks. The animals had excessive polyuria and increased requirement for sodium. The histological changes were in their distribution and the morphological structure similar to the lesions recently found in renal biopsy specimens from patients on long-term lithium treatment.