Mucinous hyperplasia in the kidney and ureter of a horse.

A case of mucinous hyperplasia in the right renal pelvis and ureter is reported in a 23-year-old, male, Quarter horse. The affected right renal pelvis was markedly distended and filled with inspissated yellowish-green mucous material compressing the adjacent cortical and medullary parenchyma. Multiple, similar masses were present protruding from the right urethral mucosa. Histologically, the masses were characterized by a cystic glandular and papillary hyperplasia of the mucosa of the renal pelvis and ureter. This is believed to be the first reported case in an equine species.