adrenal tumors

BACKGROUND

Adrenal tumors are uncommon in dogs and very rare in cats. Adrenocortical tumors and pheochromocytoma are the most common adrenal tumors. Adrenocortical tumors cause hyperadrenocorticism (or Cushing’s disease). Pheochromocytomas can be an incidental finding or produce various non-specific signs because of the release of catecholamines. Both types of adrenal tumors can invade into the adjacent caudal vena cava (major abdominal vein) and kidney. Metastasis is uncommon.

DIAGNOSIS

Diagnosis of adrenal tumors can be difficult. Screening tests (such as urine cortisol-to-creatinine ratio, low-dose dexamethasone suppression test, and ACTH stimulation test) can confirm the diagnosis of hyperadrenocorticism and differentiate whether a pituitary or adrenal tumor is responsible for causing clinical signs. Abdominal ultrasound is necessary to document the presence of an adrenal mass. Ultrasound, contrast vascular radiographs, or CT scans may be necessary to determine invasion of the tumor into either the caudal vena cava or kidney. Blood pressure measurements should also be done to test for hypertension.

CLINICAL STAGING

Abdominal ultrasound is recommended to check for metastasis to the liver and regional lymph nodes. Chest radiographs or CT scans are done to check for metastasis to the lungs.

TREATMENT

Adrenalectomy is the recommended treatment for cats and dogs with adrenal tumors. The anesthetic management can be difficult, particularly for dogs with hypertension. Alpha-antagonists (ie, phenoxybenzamine) should be administered for 10 or more days prior to surgery to help control blood pressure fluctuations during surgery. Beta-blockers may also be required if hypertension, cardiac arrhythmias and tachycardia persist despite treatment with alpha-antagonists.

Adrenalectomy can be performed through either a midline or flank approach. Combination with nephrectomy (removal of a kidney) or advanced vascular surgery may be required if there is tumor invasion into these structures. Surgical complications include pulmonary thromboembolism (especially adrenocortical tumors), hypoadrenocorticism (or adrenal insufficiency), pancreatitis, pneumonia, renal failure, and wound infections and breakdown.

Medical management of adrenocortical tumors causing hyperadrenocorticism can be attempted, but response rates and the duration of responses are shortened for dogs with adrenal-dependent compared to pituitary-dependent hyperadrenocorticism. Effective medical management of pheochromocytomas has not been reported.

PROGNOSIS

The prognosis is very good if dogs survive the perioperative period. The perioperative mortality rate is approximately 20%. The majority of dogs with adrenocortical adenomas are cured with adrenalectomy, while the median survival time for dogs with malignant adrenocortical adenocarcinomas surviving more than 14 days after surgery is 992 days. The median survival time for dogs with pheochromocytoma is 15 months.

To be updated