PAEA Surgery End Of Rotation (EOR) Practice Exam

What is the primary laboratory test used for screening pheochromocytoma?

1. Urine screen for vanillylmandelic acid

2. Blood test for norepinephrine levels

3. CT scan of the abdomen

4. Genetic testing for hereditary syndromes

The correct answer is: Urine screen for vanillylmandelic acid

The primary laboratory test used for screening pheochromocytoma focuses on the detection of metabolite levels associated with catecholamine secretion. In this case, the urine screen for vanillylmandelic acid (VMA) is particularly significant because VMA is a metabolite of catecholamines—primarily epinephrine and norepinephrine. Elevated levels of VMA in the urine are indicative of pheochromocytoma, a tumor that produces excess catecholamines, leading to symptoms such as hypertension, palpitations, and sweating. While norepinephrine levels in the blood can also be informative, urine tests for VMA provide a non-invasive method to understand overall catecholamine production in the body, making it a preferred choice in many screening protocols. Additionally, imaging studies such as CT scans can confirm the presence of a pheochromocytoma but are not used as primary screening tests. Genetic testing, while important for assessing hereditary conditions, does not serve as the initial screening for pheochromocytoma itself. Thus, measuring urinary VMA is established as a primary and effective method for screening this condition.