A patient presents with treatment-resistant hypertension and is found to have unprovoked hypokalemia on routine laboratory testing. The physician suspects primary hyperaldosteronism. Arrange the following steps of the diagnostic evaluation in the correct chronological order.
- 1Measure the ratio of plasma aldosterone concentration to plasma renin activity (PAC/PRA ratio)
- 2Perform an intravenous saline infusion test or oral sodium loading test
- 3Obtain a high-resolution computed tomography (CT) scan of the abdomen
- 4Perform bilateral adrenal venous sampling (AVS)
Answer
The correct diagnostic sequence is: 1) Measure PAC/PRA ratio, 2) Perform saline infusion test, 3) Obtain a CT scan of the abdomen, 4) Perform adrenal venous sampling.
The standard workup for primary hyperaldosteronism must follow a strict stepwise approach to avoid misdiagnosis and unnecessary surgery. First, the PAC/PRA ratio provides a highly sensitive screening tool. If positive, a confirmatory suppression test (such as saline loading) establishes the definitive biochemical diagnosis. Only after biochemical confirmation should an anatomical study (CT scan) be performed. Finally, because CT cannot differentiate between a functioning adenoma and a non-functioning incidentaloma (especially in older patients or those with bilateral nodules), adrenal venous sampling is the gold standard to prove lateralization of aldosterone secretion before surgical intervention.
Step-by-Step Solution
Key Concept
The diagnostic algorithm for primary hyperaldosteronism progresses strictly from biochemical screening to biochemical confirmation, followed by anatomical localization, and finally functional localization.