Epinephrine and norepinephrine are metabolized to metanephrine and normetanephrine. Measurement of total metanephrines in the urine is a good screen for pheochromocytoma. Measurement of creatinine output on the same sample allows determination of the metanephrine-to-creatinine ratio. This is a simple and sensitive test for pheochromocytoma, but false positive results can limit the specificity.


Patient Preparation: The patient should

(1) be resting and not be stressed

(2) not be receiving medications

(3) not have received contrast material recently.


Specimen: A 24 hour urine is preferred. Testing can be done on urines collected for shorter periods, but a short collection period can miss intermittent release of catecholamines.


urinary metanephrine-to-creatinine ratio =

= (output of metanephrine in micrograms per time period) / (output of creatinine in milligrams per time period)



• A ratio > 2.2 micrograms of metanephrine to milligram creatinine suggests pheochromocytoma

• The results are sensitive but may not be specific for pheochromocytoma



• Many drugs can cause false positives.

• Stress can cause false positives.

• Patients with hypertension from other causes can have false positive results.

• imaging contrast material can cause false negatives.

• Since excretion of catecholamines from a pheochromocytoma may be episodic, a spot urine may miss the increased release.


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