Spontaneous nephropathies in rats.

Spontaneously occurring diseases of the kidneys are very common in laboratory rats. These diseases include chronic progressive nephrosis, nephrocalcinosis, renal tubular epithelial hyaline droplets, renal tubular hypertrophy, and renal tubular basophilia. As increasing numbers of rats are used in long-term toxicity and carcinogenicity studies, recognizing spontaneously occurring renal lesions and understanding their etiology and pathogenesis are important in making an assessment of the safety of drugs and chemicals that are being tested. The purpose of this paper is to review the incidence, morphology, and pathogenesis of these spontaneous diseases. Some of the factors that alter the incidence and/or severity of these spontaneous diseases will also be discussed.