Examkin

Question

Difficulty: HardOrdering Laboratory Tests

A 6262-year-old man comes to the clinic to review the results of a recent imaging study. Two weeks ago, he was evaluated in the emergency department for severe left-sided flank pain radiating to the groin. A non-contrast computed tomography (CT) scan of the abdomen and pelvis demonstrated a 44-mm left ureteral calculus, which he subsequently passed. The CT scan also incidentally revealed a 3.23.2-cm right adrenal nodule. The nodule is well-circumscribed and homogeneous, with an unenhanced attenuation of 88 Hounsfield units. The patient has no history of malignancy and reports feeling well since passing the stone. Medical history is significant for hypertension and osteoarthritis. His medications include lisinopril, hydrochlorothiazide, and occasional ibuprofen. Blood pressure is 142/88142/88 mm Hg, pulse is 7676/min, and body mass index is 2626 kg/m 2^2. Physical examination is unremarkable, with no supraclavicular fat pads, abdominal striae, or skin thinning. Serum potassium was 4.14.1 mEq/L in the emergency department.

Which of the following is the most appropriate next step in laboratory evaluation?

  1. 1-mg overnight dexamethasone suppression test, plasma free metanephrines, and plasma aldosterone-to-renin ratioAnswer
  2. B
    1-mg overnight dexamethasone suppression test and plasma free metanephrines
  3. C
    Morning serum cortisol, plasma adrenocorticotropic hormone (ACTH), and plasma free metanephrines
  4. D
    24-hour urine collection for fractionated metanephrines and catecholamines
  5. E
    Plasma aldosterone-to-renin ratio

Answer

The most appropriate next step is to order a 1-mg overnight dexamethasone suppression test, plasma free metanephrines, and a plasma aldosterone-to-renin ratio.
This patient has an adrenal incidentaloma, defined as an adrenal mass ≥1\geq 1 cm discovered serendipitously on imaging performed for reasons other than suspected adrenal disease. All patients with an adrenal incidentaloma require a comprehensive biochemical evaluation to rule out hormonal hypersecretion, regardless of the presence or absence of overt clinical symptoms. The initial screening panel must include tests to rule out hypercortisolism (e.g., 11-mg overnight dexamethasone suppression test) and pheochromocytoma (e.g., plasma free metanephrines or 2424-hour urine fractionated metanephrines). In addition, for patients with hypertension or hypokalemia, screening for primary aldosteronism is required using the plasma aldosterone-to-renin ratio (ARR). Because this patient has a history of hypertension, he requires the complete triad of screening tests.

Step-by-Step Solution

1
Identify the clinical problem from the vignette.
The patient has an incidentally discovered 3.23.2-cm adrenal mass with benign imaging characteristics (<10<10 HU) and concurrent hypertension.
Recognizing the definition and clinical context of an adrenal incidentaloma dictates the subsequent standard diagnostic algorithm.
2
Determine the necessary baseline biochemical evaluation for all adrenal incidentalomas.
All patients, regardless of symptoms or imaging phenotype, require screening for subclinical hypercortisolism (e.g., 11-mg dexamethasone suppression test) and pheochromocytoma (e.g., plasma free metanephrines).
Subclinical hyperfunctioning adenomas are common and can cause significant metabolic morbidity or life-threatening perioperative complications if missed.
3
Determine if additional specific biochemical testing is indicated based on patient comorbidities.
The patient has hypertension, which mandates additional screening for primary aldosteronism using the plasma aldosterone-to-renin ratio.
Primary aldosteronism is a common cause of secondary hypertension and must be evaluated in incidentalomas accompanied by elevated blood pressure, even if serum potassium is normal.

Key Concept

All adrenal incidentalomas require biochemical screening for hypercortisolism and pheochromocytoma. Additional screening for primary aldosteronism (aldosterone-to-renin ratio) is required if the patient has hypertension or hypokalemia.
Rate this question

Topics

Ordering Laboratory Tests

More questions from this topic