Which test is commonly ordered to confirm pheochromocytoma by measuring metabolites?

Which test is commonly ordered to confirm pheochromocytoma by measuring metabolites?

• A. Urinalysis
• B. Urine culture
• C. 24-hour urine
• D. 8-hour urine

Answer: (C)

Measuring metabolites in a 24-hour urine collection is used to confirm pheochromocytoma because the tumor releases catecholamines in episodic bursts, and their breakdown products (metanephrine, normetanephrine, and often VMA) are excreted in urine over the entire day. A 24-hour collection captures the total daily excretion, providing a more reliable picture of whether there’s excess catecholamine production than a single spot sample. Urinalysis or urine culture don’t assess these metabolites, and an 8-hour urine would miss portions of the day, risking missed peaks.

Measuring metabolites in a 24-hour urine collection is used to confirm pheochromocytoma because the tumor releases catecholamines in episodic bursts, and their breakdown products (metanephrine, normetanephrine, and often VMA) are excreted in urine over the entire day. A 24-hour collection captures the total daily excretion, providing a more reliable picture of whether there’s excess catecholamine production than a single spot sample. Urinalysis or urine culture don’t assess these metabolites, and an 8-hour urine would miss portions of the day, risking missed peaks.