A four-year-old male Saint Bernard dog with a scrotal hydrocele was referred with a history of scrotal swelling and emaciation. Physical and hematological evaluation revealed dirofilaria infestation and liver function abnormalities. Ultrasonography showed fluid collection in each peritesticular area and in the peritoneal cavity. The dog survived only 10 days after the initial presentation. At necropsy, umbilicated nodular masses in the liver, hemorrhagic ascites, heart dirofilariasis, and accumulated transudate in the scrotum were observed. Histopathologic and immunofluorescence examination revealed cholangiocarcinoma in the liver, indicating the cause of liver failure and ascites accumulation. Severe edema was seen in the mediastinal connective tissue of spermatic cord and heartworm DNA from the spermatic cord tissue was detected by polymerase chain reaction (PCR) analysis. In the present case, it was suspected that the acquired hydrocele might have been caused by ectopic migration of filarial worms or by severe hypoproteinemia induced by liver failure.

Key words: Dirofilaria; Dog; Hydrocele; Hypoproteinemia; Liver; Scrotum