Pheochromocytoma in 50 dogs.

Fifty dogs with pheochromocytoma were identified in a retrospective study of a 9-year period. For 24 of 50 dogs (48%), the tumor was an incidental finding during necropsy or surgery. Presenting signs were referrable to the nervous system in 7 of the 26 symptomatic dogs (27%); were referrable to the cardiopulmonary system in 7 of 26 dogs (27%); or were nonspecific, reflecting general systemic disease, in 17 of 26 dogs (65%). Abnormal clinical findings were highly varied but were also generally referrable to the cardiopulmonary and nervous systems. Six of 7 dogs (86%) evaluated were hypertensive (systolic range, 164 to 325 mm Hg; diastolic range, 110 to 198 mm Hg). Serum biochemical findings were nonspecific, although 11 of 39 dogs (28%) were hypercholesterolemic. Abdominal fluid samples were analyzed in 6 dogs; 3 were nondiagnostic, and 3 were interpreted as lymphosarcoma. The imaging studies that were of most value included abdominal radiographs (mass identified in 9 of 16 dogs [56%]), caudal vena caval angiography (tumor thrombus correctly diagnosed in 4 of 7 dogs [57%]), and abdominal ultrasonography (mass seen in 5 of 6 dogs [83%] and tumor thrombus seen in 3 of 5 dogs [60%]). Local tumor invasion was present in 26 of 50 dogs (52%), regional lymph node metastases in 6 of 50 dogs (12%), and distant metastases in 12 of 50 dogs (24%). Cause of death was tumor-related in 19 of 50 dogs (38%) and non-tumor related in 28 of 50 dogs (54%).