Microfilaria in the Urine of a Dog with Concurrent Urinary Bladder Sarcoma.

A 12 yr old female spayed American Staffordshire terrier was referred for stranguria, pollakiuria, and concern for a mass in the trigone of the urinary bladder. A urinalysis and abdominal ultrasound were performed to further investigate the bladder mass. Nematode larvae were identified in the urine, termed microfilaruria, while a caudal abdominal mass was found on ultrasound impinging on the urethra. Fine-needle aspirate of the abdominal mass revealed malignant neoplasia. A SNAP 4Dx of the peripheral blood was positive for Dirofilaria immitis antigen and a modified Knott's test confirmed D immitis larvae. The patient was euthanized owing to poor prognosis, and multiple masses were found within the abdominal cavity that, based on histopathology and immunohistochemistry, were diagnosed as poorly differentiated sarcoma. Hemorrhage, secondary to the abdominal mass, was considered the primary cause of microfilaruria.