Vaginal Bleeding and an Intra-Abdominal Mass in a Sprague-Dawley Rat (Rattus norvegicus)

A 2-year-old female Sprague-Dawley rat (Rattus norvegicus) presented with mild vaginal bleeding and no additional clinical signs. Physical examination revealed a firm intra-abdominal mass and unilateral renal enlargement. Diagnostic evaluation including CBC, serum chemistry, and CT identified neutrophilia, metabolic abnormalities, and a large abdominal mass causing displacement of abdominal organs. Differential diagnoses included urinary tract infection, reproductive tract disease, and neoplasia. Due to poor prognosis, humane euthanasia was performed. Necropsy and histopathology revealed uterine adenocarcinoma with pulmonary metastasis. Splenomegaly was also identified, consistent with disseminated large granular lymphocyte leukemia involvement. This case demonstrates that subtle clinical abnormalities in aged laboratory rats may represent severe disseminated neoplastic disease.