What is the appropriate monitoring and laboratory follow-up for a 12 mm benign adrenal nodule with characteristics suggestive of an adrenal adenoma, given elevated aldosterone levels and low renin levels?

From the Guidelines

Appropriate Monitoring and Laboratory Follow-up

The patient with a 12 mm benign adrenal nodule and characteristics suggestive of an adrenal adenoma, given elevated aldosterone levels and low renin levels, should undergo confirmatory testing to diagnose primary aldosteronism, as the initial screening with aldosterone-to-renin ratio is suggestive but not definitive 1.

• The aldosterone-to-renin ratio is the most accurate and reliable means of screening for primary aldosteronism, with a cutoff value of 30 when plasma aldosterone concentration is reported in nanograms per deciliter (ng/dL) and plasma renin activity in nanograms per milliliter per hour (ng/mL/h) 1.
• Confirmatory tests such as the intravenous saline suppression test or oral salt-loading test should be performed to confirm the diagnosis of primary aldosteronism 1.
• Adrenal venous sampling is considered the standard for distinguishing between unilateral and bilateral adrenal hyperplasia and should be considered if the patient is a surgical candidate 1.
• For patients with elevated aldosterone levels and low renin levels, medical management with spironolactone or eplerenone may be considered for hypertension and hypokalemia, especially if the patient is not a surgical candidate or has bilateral adrenal hyperplasia 1.
• Follow-up imaging with CT or MRI may be considered to assess the nature of the adrenal nodule, especially if the initial imaging is indeterminate 1.
• Endocrinologic evaluation should be considered to assess for subclinical hyperfunction, which is present in 5% of adrenal incidentalomas 1.

From the Research

Monitoring and Laboratory Follow-up

The appropriate monitoring and laboratory follow-up for a 12 mm benign adrenal nodule with characteristics suggestive of an adrenal adenoma, given elevated aldosterone levels and low renin levels, can be guided by the following points:

• Initial evaluation should aim to rule out malignancy and functionality, including a detailed clinical history, radiographic assessment, and complete blood chemistry and hormone study 2.
• For patients with hypertension, evaluation for hyperaldosteronism is recommended, which can be done through measurements of aldosterone and plasma renin activity 3.
• Given the size of the nodule (12 mm) and the presence of elevated aldosterone levels, biochemical follow-up is warranted to exclude a functioning mass 4.
• Annual biochemical follow-up for up to 5 years may be reasonable, especially if the tumor is more than 3 cm in size 3. However, for smaller nodules like the one in question, repeat computed tomography study in 3-6 months and then yearly for 2 years may be considered 3.
• The American College of Radiology incidental adrenal White Paper provides a structured algorithm for management of incidental adrenal nodules, which can guide further diagnostic testing and follow-up 4.

Laboratory Tests

The following laboratory tests may be considered for follow-up:

• Aldosterone-to-renin ratio to confirm the presence of primary hyperaldosteronism 5.
• Dexamethasone suppression test to rule out autonomous cortisol secretion 2.
• Plasma metanephrines to evaluate for pheochromocytoma 3.
• Complete blood chemistry to monitor for any changes in electrolyte levels or other parameters 2.

Imaging Follow-up

Imaging follow-up can be guided by the size and characteristics of the nodule, as well as the presence of any suspicious features:

• For nodules less than 4 cm, adrenal computed tomography is the most appropriate test for further evaluation 4.
• Repeat imaging studies can be performed at 3-6 months and then yearly for 2 years to monitor for any changes in size or characteristics 3.
• If the lesion remains stable and there are no indeterminate characteristics, no additional radiographic studies may be needed 2.