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Difficulty: MediumDiagnostic Workup and Test Sequencing

A 43-year-old man presents for a follow-up evaluation of hypertension. He reports strict adherence to his prescribed regimen of maximum-dose amlodipine, lisinopril, and hydrochlorothiazide, but his home blood pressure readings remain consistently elevated. Today in the clinic, his blood pressure is 165/102 mm Hg. Laboratory studies reveal a serum potassium level of 2.9 mEq/L and a normal serum creatinine. The physician suspects secondary hypertension due to primary hyperaldosteronism. Arrange the following diagnostic steps in the correct order for evaluating this patient's suspected condition, from initial screening to preoperative assessment.

  1. 1Measurement of plasma aldosterone concentration and plasma renin activity
  2. 2Intravenous saline infusion test
  3. 3High-resolution computed tomography of the abdomen
  4. 4Adrenal venous sampling

Answer

The correct sequence is: Measurement of plasma aldosterone concentration and plasma renin activity, followed by Intravenous saline infusion test, then High-resolution computed tomography of the abdomen, and finally Adrenal venous sampling.
The evaluation of primary hyperaldosteronism is rigorously tiered to prevent unnecessary invasive testing and erroneous diagnoses. The sequence begins with the plasma aldosterone-to-renin ratio as a high-sensitivity screening tool. If elevated, the diagnosis must be confirmed by demonstrating autonomous aldosterone secretion via a suppression test, such as an intravenous saline infusion. Only after biochemical confirmation is imaging with an adrenal protocol CT scan pursued to rule out large carcinomas and assess adrenal anatomy. Finally, because nonfunctioning adrenal incidentalomas are common and bilateral hyperplasia can sometimes appear asymmetrical on imaging, adrenal venous sampling is required prior to surgery to definitively prove that aldosterone hypersecretion is unilateral.

Step-by-Step Solution

1
Identify the need for screening.
The patient has resistant hypertension and spontaneous hypokalemia, prompting screening with the aldosterone-to-renin ratio.
Resistant hypertension accompanied by unprovoked or diuretic-induced hypokalemia is highly suspicious for primary hyperaldosteronism.
2
Determine the next step after a positive screen.
Proceed to confirmatory testing with an intravenous saline infusion test or oral sodium loading.
A high screening ratio is not definitive; autonomous aldosterone production must be confirmed by demonstrating a lack of suppression with salt loading.
3
Select the initial localization study.
Obtain a high-resolution CT scan of the abdomen.
Imaging is indicated only after biochemical confirmation to look for large masses or adrenal carcinomas, though it cannot definitively distinguish between functional adenomas and nonfunctioning incidentalomas.
4
Determine the final preoperative assessment.
Perform adrenal venous sampling.
Because adrenal incidentalomas are common in the general population, adrenal venous sampling is necessary to prove unilateral aldosterone hypersecretion before offering a surgical cure (adrenalectomy).

Key Concept

The diagnostic sequencing for primary hyperaldosteronism strictly proceeds from screening (aldosterone/renin ratio) to confirmation (saline suppression), followed by localization (CT scan), and finally preoperative functional lateralization (adrenal venous sampling).
Estimated Time:1m 30s
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Diagnostic Workup and Test Sequencing

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