17. Readful! Adrenal adenoma with Matt Morgan and Evan Siegelman
May 15, 2023
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In this engaging discussion, Matt Morgan, a radiologist from the University of Pennsylvania, teams up with adrenal adenoma expert Evan Siegelman. They dive deep into diagnosing adrenal lesions, dissecting Hounsfield units and washout values. A quirky twist on the Monty Hall problem highlights the complexities of probability. The duo also shares their favorite medical quotes, intertwining humor with clinical insights, and tackles the delightful confusion of left versus right in radiology. Expect a mix of knowledge and entertainment!
Adrenal adenomas are primarily benign lesions discovered incidentally, necessitating differentiation from malignancies, especially in cancer patients.
Imaging techniques, particularly CT and MRI, are vital for accurately characterizing adrenal adenomas and guiding subsequent management decisions.
Functional adrenal adenomas can cause serious hormonal conditions, highlighting the need for clinical evaluation of blood pressure and hormonal status.
Deep dives
Introduction to Adrenal Adenomas
Adrenal adenomas are the most prevalent type of adrenal lesion, frequently discovered incidentally during imaging for unrelated reasons. These lesions can be benign but must be differentiated from adrenal metastases or malignancies, especially in patients with a history of cancer. The terminology often used, such as 'incidental adrenal lesion' or 'incidentaloma,' can be misleading as it encompasses various pathologies and might cause confusion in clinical contexts. When assessing adrenal lesions, understanding the underlying characteristics of adrenal adenomas, especially their imaging features, is essential for accurate diagnosis and management.
Imaging Features and Differentiation
Imaging plays a crucial role in evaluating adrenal adenomas, with computed tomography (CT) being the primary modality. Typical characteristics of benign adenomas include low attenuation (Hounsfield units) and smooth margins, which usually indicate they are less than three centimeters in size. For lesions showing atypical features such as hemorrhage, necrosis, or calcification, malignancy should be considered, particularly if the lesion exceeds four centimeters in size. The differentiation from other entities such as pheochromocytomas and adrenal metastases is crucial, as they may show similar imaging characteristics and washout kinetics on CT scans.
Functional Versus Non-Functional Adenomas
The majority of adrenal adenomas are non-functional, meaning they do not secrete hormones, and are often asymptomatic. However, those that are functional can lead to conditions such as Cushing's syndrome or Conn's syndrome, characterized by excess hormone production. Clinical evaluation should always consider the patient's blood pressure and hormonal status to identify potential end-organ effects resulting from hyperfunctioning adenomas. Systematic follow-up, using resources such as the American College of Radiology white paper, helps guide management strategies for incidental adrenal masses, ensuring proper surveillance and intervention when necessary.
Chemical Shift Imaging and MRI
Magnetic resonance imaging (MRI), particularly chemical shift imaging, is integral in characterizing adrenal lesions, especially when CT findings are inconclusive. Signal dropout on opposed-phase imaging is indicative of an adenoma, with a drop in signal intensity above a specified threshold considered diagnostic. Notably, lesions with Hounsfield units exceeding 30 on CT often do not demonstrate the lipid content required for reliable diagnosis via chemical shift MRI. It’s essential to understand the limitations of MRI when interpreting adrenal lesions, as false positives can arise due to overlapping features in fat-containing malignancies such as hepatocellular carcinoma and renal cell carcinoma.
Management and Prognostic Considerations
Management decisions for adrenal adenomas hinge on the size and functional status of the lesions, with small, non-functional adenomas often left in situ. Surgical intervention may be warranted for lesions larger than four centimeters or those demonstrating hormonal activity. Studies indicate that many adenomas are stable or even regress over time, underscoring the importance of individual patient assessment and monitoring. Understanding pre-test probabilities and the clinical context is crucial, as most incidental adrenal masses found in patients without a known malignancy are likely benign, decreasing the urgency for invasive procedures.
It's radiology, but read to you! Matt reads the Radiopaedia adrenal adenoma article to his University of Pennsylvania abdominal imaging colleague Dr Evan Siegelman who adds his expert insights. Meanwhile, Frank tries to win a car!
