Abstract
Apparently normal urinary bladder of beagle dogs of both sexes were examined histopathologically. Materials were obtained from fifty autopsied aged beagle dogs and six autopsied young beagle dogs. Changes of urinary bladder epithelium were classified into five types: Brunn's nest, squamous metaplasia, lymphocytic infiltration, epithelial hyperplasia, and atypia. Brunn's nests in aged dogs were found at all ages and in both sexes. Squamous metaplasia in aged dogs was found in 25.0% of males and 50.0% of females. Scattered lymphocytic infiltration in aged dogs could be observed in 18.0% of both sexes. Epithelial hyperplasia and atypia in aged dogs were found in 82.0% and 28.0% of cases, respectively; however, no difference between sexes was found. Sites of predilection for Brunn's nests were the trigone and anterior wall; however, those for other types of lesion were not found. As for young dogs, Brunn's nests were found in 66.7% of both sexes, and sites of predilection were the trigone and anterior wall; the other lesions were not observed. These chronic changes of urinary bladder epithelium in aged beagle dogs should be considered in the studies of bladder carcinogenesis and natural history of bladder tumor in dogs.
