Renal Papillary Hyperplasia

Intermittent hematuria has been reported in hybrid Lewis ? Brown Norway rats. The syndrome occurred pre­dominantly in males, but it also occurs in females. Some, but not all, of the rats had concommitant unilateral or bilateral hydronephrosis.

FIG. 2.67. Renal papilla from adult rat with a history of hematuria. Note the proliferative vascular malformations with eroded surfaces and hemorrhage.

Degenerative Osteoarthritis

Erosion of the articular cartilage occurs in sites such as the sternum and femur in aged rats, with degeneration of cartilaginous matrix, clefting, and cyst formation.