For pheochromocytoma, which test is commonly completed on admission to help determine the diagnosis?

• A. 24-hour urine collection.
• B. Chest x-ray.
• C. Arterial blood gas.
• D. Electroencephalogram.

Answer: (A)

Pheochromocytoma causes excess catecholamine production, which can be episodic. Measuring these substances over a full day provides a reliable signal of ongoing excess. The 24-hour urine collection for catecholamines and their metabolites captures secretion across variations and helps confirm the diagnosis, guiding subsequent imaging to locate the tumor. By contrast, chest x-ray, arterial blood gas, and EEG don’t assess catecholamine excess and aren’t useful for diagnosing pheochromocytoma. Modern practice may also use plasma free metanephrines, but a 24-hour urine test remains a common admission test to help establish the diagnosis.