Diagnostic Imaging in Canine Pheochromocytoma

Abstract

The diagnosis of pheochromocytoma is challenging due to the variable presentations of patients affected with this neoplasm. This report describes four dogs with pheochromocytoma in which radiography, ultrasonography and computed tomography (CT) were key diagnostic tools. Computed tomography was the most useful imaging modality for assessment of size, shape and margination of the tumor. CT findings for the pheochromocytoma included a large, irregularly shaped mass in the dorsal midabdomen with multiple foci of low attenuation dispersed in hyperdense, highly vascular tissue. This neoplasm often invades the caudal vena cava and other surrounding organs therefore, although a pheochromocytoma may be identified in the absence of clinical signs, it should not be considered an incidental lesion. The unpredictable growth rate and potential for invasion of major vessels warrants serious consideration. Follow-up ultrasound and CT examinations are recommended for patients with adrenal masses that do not undergo surgical excision.

Ultrasonographic features of adrenal gland lesions in dogs can aid in diagnosis

“…Larger pheochromocytoma seemed to be more heterogeneous, with predominant cystic-necrotic areas. Vascular tumor thrombus was present in 40% of cases, but without distant metastases, consistent with observations by Rosenstein [23]. In humans, pheochromocytoma is usually a benign tumor and as such is not expected to invade adjacent tissues [1].…”

Adrenal Glands

“…In the more recent study, a left adrenal gland diameter of less than 3.2 mm was strongly suggestive of hypoadrenocorticism when compared to healthy dogs. 7,45,48,63,64 A careful search of adjacent structures, other abdominal organs, and thoracic radiographs to rule out metastasis is recommended when an adrenal tumor is suspected. However, CVC thrombosis in the absence of an adrenal tumor must also be considered because of the hypercoagulable state that accompanies hyperadrenocorticism.…”

“…65 However, biopsy of pheochromocytomas is not recommended because a hypertensive crisis may result. 7,45,67,68 Hemorrhage, fatal hypertensive crisis, or arrhythmic episodes associated B document persistent hypertension with pheochromocytomas. 7,45,67,68 Hemorrhage, fatal hypertensive crisis, or arrhythmic episodes associated B document persistent hypertension with pheochromocytomas.…”

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] CT and MRI are advantageous because they can be used to evaluate the pituitary gland concurrently. These modalities have also been used to image the adrenal glands in small animals.…”

Imaging in Oncology

“…9 CT is also useful to determine the origin and extent of abdominal mass lesions, and compared to ultrasonography, CT can better document the relationship of a mass with surrounding anatomic structures (Figure 6-5). 18,19 Infiltrative muscular lesions such as infiltrative lipomas and soft tissue sarcomas are routinely imaged with CT for both surgical and radiotherapy planning. 12,20 A contrast-enhanced scan is essential during CT to improve visualization of tumor margins, especially for infiltrative tumors such as feline vaccine-associated sarcomas.…”