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Pheochromocytoma in dogs and cats

Description
Pheochromocytoma is a tumor of the adrenal gland. Specifically, it develops in the adrenal medulla, the center of the gland. The adrenal glands are located next to the kidneys (one next to each kidney). The adrenal medulla secretes the hormones epinephrine and norepinephrine. Epinephrine, also known as adrenalin, is secreted in response to stress. Epinephrine and norepinephrine cause a variety of changes in the body, the most common of which is high blood pressure. Both of these hormones are produced excessively by the pheochromocytoma tumor. Pheochromocytomas can be benign or malignant. Pheochromocytomas are uncommon in dogs and rare in cats.



Additional information


A catecholamine-producing tumor of chromaffin cells of the adrenal medulla.

Pathophysiology
  • Pheochromocytomas can be benign or malignant. Clinical signs are caused by invasion by the tumor or overproduction of catecholamines. Local invasion may cause tumor thrombosis of the posterior vena cava, resulting in abdominal distension, ascites, or peripheral edema. Distant metastases to the lymphatics, lungs, liver, and kidneys may develop after invasion of the great vessels.
  • Functional pheochromocytomas produce norepinephrine, both norepinephrine and epinephrine, or, less commonly, dopamine. Overproduction of catecholamines by a pheochromocytoma may be episodic or continuous depending on the secretory pattern of the tumor. Catecholamine excess may cause a myriad of physiologic changes, the most common of which is systemic hypertension. Although chronic episodic signs are most common, acute hypertensive crisis with cardiac arrhythmias can cause sudden collapse and death. Rupture of these highly vascular, intraabdominal tumors can cause acute hypovolemic shock.

    Systems Affected
  • Cardiovascular Because of the hypertensive effects of catecholamines

    Genetics
    Pheochromocytoma may be inherited as an autosomal dominant trait in humans; heritability has not been determined in animals.

    Incidence/Prevalance
    Uncommon in dogs and rare in cats.
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