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Pheochromocytoma 785

Technician Tips Never leave bottles of medications on counters AUTHOR: Judy K. Holding, DVM, RN
Monitor blood pressure and for ventricular or other areas that pets may be able to reach. EDITOR: Tina Wismer, DVM, MS, DABVT, DABT
VetBooks.ir Client Education SUGGESTED READING Diseases and Disorders
arrhythmias.
Holding J: Phenylpropanolamine toxicosis in dogs
Chewable formulations increase the likelihood
that pets will ingest a large number of tablets. and cats. Vet M 107:18-19, 2012.

Video
Pheochromocytoma Available Client Education
Sheet

BASIC INFORMATION tremors, blindness, retinal hemorrhage/ a cortisol-secreting adrenocortical tumor, serum
detachment, and signs of abdominal pain. inhibin can be measured, if available; if inhibin
Definition • An abdominal mass is not usually palpable. is detectable in serum, an adrenal gland tumor
Catecholamine-producing tumor derived is most likely cortical, and an undetectable level
from adrenal medulla chromaffin cells (most Etiology and Pathophysiology is highly supportive of a pheochromocytoma.
common) or extraadrenal sympathetic ganglia • Tumors usually are solitary, slow growing, and Definitive diagnosis requires histopathologic
(paragangliomas). Most involve a single adrenal highly vascular. Rarely, bilateral pheochro- exam of the excised adrenal gland.
gland (90%), but 10% are bilateral. Tumor mocytomas or adrenal pheochromocytomas
hormone secretion is episodic and sporadic. with a contralateral adrenocortical tumor Differential Diagnosis
have been reported. • Adrenal mass
Epidemiology • Clinically detected pheochromocytomas are ○ Nonfunctional adrenal mass
SPECIES, AGE, SEX considered to be malignant in at least 50% of ○ Functional adrenocortical mass
• Dogs: uncommon; middle-aged/older (mean, cases, with local invasion (e.g., caudal vena • Systemic hypertension; other causes such as
11 years; range, 1-18 years) cava) and metastasis to liver and regional renal disease or hyperadrenocorticism may
• Cats: rare; older (mean, 14.5 years) lymph nodes most common. need to be investigated.
• Clinical signs related to excessive cate- • Collapse/weakness; other causes such as
ASSOCIATED DISORDERS cholamine secretion (most common) and/ hypoglycemia, cardiac or respiratory disease
• May occur as part of multiple endocrine or from space-occupying or invasive behavior may need to be investigated.
neoplasia syndrome of the tumor or from distant metastasis (less • Sinus tachycardia; other causes such as
• Concurrent tumors can include cortisol- common). systemic disease or anxiety/excitement/pain
secreting adrenocortical tumors, adreno- • Excess catecholamines cause arteriolar should be considered.
corticotrophic hormone-secreting tumors or vasoconstriction and systemic hypertension,
hyperplasia, thyroid tumors and insulinomas cardiac arrhythmias, mydriasis, increased Initial Database
• Non-endocrine tumors may occur smooth muscle sphincter tone, and increased • CBC, serum biochemical profile, and
concurrently. hepatic gluconeogenesis and glycogenolysis. urinalysis: normal or may show nonspecific
changes (e.g., mild nonregenerative anemia,
Clinical Presentation mature neutrophilia, increased liver enzymes,
HISTORY, CHIEF COMPLAINT DIAGNOSIS proteinuria)
• Antemortem diagnosis is challenging because Diagnostic Overview • Multiple arterial blood pressure (BP) mea-
clinical signs are varied, intermittent, and A presumptive diagnosis rests on identifica- surements (p. 1065): hypertension (sustained
often nonspecific. tion of an adrenal mass and concurrent, systolic pressure > 160 mm Hg and/or
Dogs: often episodic cardiovascular abnormalities diastolic pressure > 100 mm Hg) is well
• Intermittent weakness, lethargy, and collapse (e.g., sinus tachycardia; premature ventricular recognized (40% of cases), but normoten-
most common; panting/tachypnea, agitation, complexes; systemic hypertension; syncope; sion does not rule out a pheochromocytoma
anorexia, weight loss, polyuria and polydipsia pulmonary thromboembolism) ± testing to because tumor catecholamine secretion is
(PU/PD), tachycardia, vomiting, diarrhea, document elevations in urine or plasma cat- intermittent.
seizures, or sudden death possible echolamines (epinephrine and norepinephrine) • Abdominal radiographs: low sensitivity for
• Signs often episodic and complicated by a and catecholamine metabolites (metanephrine detecting pheochromocytomas but may
high incidence of concurrent disease and normetanephrine). Measurement of cat- reveal a perirenal mass ± mineralization.
• Many show no clinical signs, and the diag- echolamines and catecholamine metabolites • Thoracic radiographs: pulmonary metastasis in
nosis is made incidentally during abdominal is recommended; catecholamines are secreted 10% of affected dogs; cardiomegaly, or pulmo-
ultrasonography or necropsy. episodically, and metabolites (metanephrines) nary edema or congestion (rare). Pulmonary
Cats: are secreted continuously from the tumor. No thromboembolism (p. 842) is recognized with
• Vague signs, with PU/PD, lethargy, and consensus exists on preference for plasma or pheochromocytoma and may cause tachypnea
anorexia most common urine testing. If urine used, normetanephrine and, rarely, acute cor pulmonale and/or right-
to creatinine ratio has higher sensitivity and sided congestive heart failure.
PHYSICAL EXAM FINDINGS specificity than metanephrine, epinephrine, • Electrocardiography (ECG [p. 1096]):
• Physical exam commonly unremarkable or norepinephrine to creatinine ratios for the intermittent or sustained tachycardia (sinus
• Potential abnormalities include tachypnea, diagnosis. Similarly, measurement of plasma tachycardia, ventricular arrhythmias) is
generalized weakness (often episodic), free normetanephrine is superior to measure- common. A 24-hour Holter monitor (p. 1120)
tachycardia or other cardiac arrhythmias, ment of free epinephrine, norepinephrine, may be needed to document intermittent
pale mucous membranes, epistaxis, muscle or metanephrine. To help differentiate from arrhythmias.

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