Renal Failure and Bilateral Thymoma in an American Bullfrog, Rana catesbiana

Abstract

An adult female American bullfrog, Rana catesbiana, from a zoological collection, was examined because of a slowly progressive distension of the coelomic cavity. Approximately 750 cc of clear fluid was removed by celiocentesis. Using cardiocentesis, a blood sample was obtained and plasma was removed for biochemical analyses. The frog was kept in a isotonic solution of saline that contained calcium gluconate, and enrofloxacin was administered orally for 17 d. The frog was found dead in its cage at 17 d following removal of the coelomic fluid and was submitted for necropsy. Major gross findings were cystic kidneys and bilateral cystic masses in the cervical region. Using light microscopy, glomeruli were swollen and were surrounded by thick rims of dense fibrous connective tissues; some also were sclerotic. Additionally there was chronic, dif fuse, severe tubulointerstitial nephritis. The bilaterally symmetrical cystic masses in the cervical region had microscopic features most consistent with those of the thymus and the diagnosis was thymoma. This repre sents the first report of chronic renal disease and thymoma in an amphibian.