Plasma free metanephrines in healthy cats, cats with non-adrenal disease and a cat with suspected phaeochromocytoma

Abstract

Phaeochromocytomas are catecholamine-secreting tumours of the adrenal glands and are rare in cats. Plasma metanephrine levels are widely considered the diagnostic test of choice for phaeochromocytoma in people but have not been investigated in cats. In this study plasma free normetanephrine and metanephrine levels were measured using high-pressure liquid chromatography in healthy cats, sick cats with non-adrenal disease and in a cat with a suspected phaeochromocytoma. Plasma normetanephrine was significantly higher in sick cats with non-adrenal disease compared to healthy cats (P<0.05) and markedly higher in the cat with a suspected phaeochromocytoma when compared to either group. Plasma metanephrine was not significantly different in any of the groups. This study establishes a first-line guide reference range for plasma metanephrine and normetanephrine levels in healthy cats and cats with non-adrenal disease. These results provide rationale for further studies to establish the use of plasma normetanephrine levels as a potential diagnostic test for phaeochromocytoma in the cat.

Pheochromocytoma and Multiple Endocrine Neoplasia

“…Plasma-free metanephrine was not different (Wimpole et al, 2010). Plasma-free normetanephrine was found to be markedly higher in the one cat with suspected pheochromocytoma compared to healthy cats and cats with non-adrenal diseases.…”

Blood Pressure Measurements in 780 Apparently Healthy Cats

“…8 Diseases associated with secondary systemic hypertension in the cat include chronic kidney disease, 9,10 hyperthyroidism, 9 primary hyperaldosteronism, 11 and pheochromocytoma. 12 If none of these diseases are present, and stress-related effects on blood pressure ("white-coat hypertension") 13 have been excluded, then cats with persistent hypertension are considered to have idiopathic hypertension. However, it can be difficult to definitively rule out subclinical renal disease or primary hyperaldosteronism, which can make an unconditional diagnosis of idiopathic hypertension difficult.…”

Pheochromocytoma

“…2 Measurement of urinary catecholamine concentrations (metanephrine, normetanephrine, vanillylmandelic acid) as a spot check referenced to urine creatinine, or over a 24-hour period, is performed in humans with suspected pheochromocytomas and has been investigated in dogs. 30 Because of the similarity in clinical signs and ultrasonographic appearance of pheochromocytomas and adrenocortical tumors, and reports of the coexistence of hyperadrenocorticism and pheochromocytoma, hyperadrenocorticism should be ruled out at the time of medical workup. 29 Secondary factors, such as excitement, exercise, vanilla-containing foods, phenoxybenzamine therapy, and radiographic contrast agents may result in false-positive elevations.…”

“…7,29 One study showed that dogs with hyperadrenocorticism had increased concentrations of urinary catecholamines and normetanephine compared with normal dogs, and a high (four times normal) concentration of urinary normetanephrine was highly suggestive of pheochromocytoma. 30 A thorough abdominal exploration is recommended during surgery to identify gross metastatic disease. 2 Plasma metanephrine level measurements have recently been described in cats, including one cat with a suspected pheochromocytoma.…”