The addition of an excess of inorganic phosphate in the form of orthophosphoric acid, acid, basic or neutral sodium or potassium phosphate to the diet of albino rats results in the development of an interesting and permanent renal lesion.

The phosphate renal lesion is characterized by a necrosis of the cells of the convoluted tubules commencing at the terminal end, followed by a regeneration of atypical epithelium and calcification of the necrotic debris that fills the tubules.

The entire outer stripe of the outer zone of the medulla is transformed into a zone of distorted structures and there is an increase in the interstitial connective tissue. The adjoining cortex is also involved with cystic dilatation of tubules and collapse. Such areas may reach the free surface of the organ and produce a retracted scar.

In the gross the kidneys are enlarged and firm on section with a pebbled surface produced by numerous scars.

The maximum changes in the kidney structure are reached after some 15 days although necrosis of the convoluted tubule cells is evident after a single day of phosphate feeding.

The renal structure is not restored to its normal form when the excess of phosphate is removed from the diet.

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