Examkin

Question

Difficulty: MediumInterpreting Imaging Results

A 54-year-old woman is evaluated in the clinic following a recent emergency department visit for right-sided flank pain. During her acute presentation, a noncontrast computed tomography (CT) scan of the abdomen and pelvis confirmed a 3-mm right ureteral calculus, which she has since passed spontaneously. However, the radiologist's report notes an incidental 3.5-cm solid, well-circumscribed mass in the left adrenal gland. The mass is homogeneous and has an attenuation value of 5 Hounsfield units (HU). The patient has no significant past medical history and takes no medications. She feels well and reports no headaches, palpitations, weakness, or diaphoresis. Her blood pressure is 120/78 mm Hg, and her pulse is 72/min. Physical examination is unremarkable.

Based on the interpretation of the imaging results, which of the following best describes the nature of this finding and the most appropriate next step in management?

  1. Benign lipid-rich adenoma; proceed with biochemical testing for hormone hypersecretionAnswer
  2. B
    Indeterminate mass; obtain contrast-enhanced magnetic resonance imaging
  3. C
    Suspicious for malignancy; schedule an image-guided percutaneous biopsy
  4. D
    Likely adrenocortical carcinoma; refer for immediate surgical resection
  5. E
    Benign nonfunctioning adenoma; provide reassurance with no further evaluation required

Answer

The correct response identifies the mass as a benign lipid-rich adenoma and correctly recommends proceeding with biochemical testing for hormone hypersecretion.
The correct answer accurately interprets the imaging findings and identifies the standard-of-care next step. On a noncontrast CT scan, an attenuation value of less than 10 Hounsfield units (HU) is diagnostic of a benign, lipid-rich adrenal adenoma. Because the imaging phenotype definitively establishes the anatomic diagnosis as benign, no further imaging characterization (e.g., contrast CT, MRI) or biopsy is indicated. However, structural imaging cannot determine the functional status of the mass. Current guidelines mandate that all adrenal incidentalomas larger than 1 cm undergo biochemical evaluation to rule out subclinical hormone hypersecretion (such as subclinical Cushing syndrome and pheochromocytoma), regardless of the presence or absence of clinical symptoms. Therefore, proceeding with functional biochemical testing is the most appropriate next step.

Step-by-Step Solution

1
Interpret the specific imaging characteristics of the incidental adrenal mass provided in the vignette.
The mass is 3.5 cm, homogeneous, and has an attenuation of 5 Hounsfield units (HU) on a noncontrast CT scan.
Accurate interpretation of Hounsfield units is required to determine the malignant potential of adrenal incidentalomas.
2
Correlate the attenuation value with the differential diagnosis of adrenal masses.
An attenuation value of <10 HU is highly specific for a lipid-rich adrenal adenoma, which is benign and does not require further anatomic imaging.
Recognizing benign imaging phenotypes prevents the overutilization of unnecessary advanced imaging modalities.
3
Determine the required management sequence for a newly discovered, benign-appearing adrenal mass.
Biochemical testing (e.g., 1-mg overnight dexamethasone suppression test and plasma free metanephrines) is required for all incidentalomas >1 cm.
Subclinical hormone hypersecretion can occur in up to 15% of patients with radiographically benign adenomas, dictating the need for functional evaluation.

Key Concept

On noncontrast CT, an adrenal mass with an attenuation of <10 Hounsfield units is diagnostic of a benign lipid-rich adenoma; however, all adrenal incidentalomas >1 cm must still undergo biochemical testing to rule out subclinical hormone hypersecretion.
Rate this question

Topics

Interpreting Imaging Results

More questions from this topic