An adrenal incidentaloma is a mass or growth found in an adrenal gland, discovered unexpectedly during an imaging scan performed for an unrelated medical reason. These findings are “incidental” because the scan was not initially ordered to investigate an adrenal problem. The increasing use of advanced imaging techniques like CT and MRI has led to a rise in their detection. While many adrenal incidentalomas are harmless, a small percentage can be serious, requiring careful evaluation.
Adrenal Glands Explained
The adrenal glands are small, triangular-shaped endocrine glands situated on top of each kidney. Each gland consists of two distinct parts: the outer adrenal cortex and the inner adrenal medulla. The cortex produces steroid hormones like cortisol and aldosterone. Cortisol regulates metabolism, immune function, and stress response, while aldosterone maintains blood pressure and controls salt and water balance.
The adrenal medulla produces hormones like adrenaline and noradrenaline. These hormones are involved in the body’s “fight-or-flight” response, influencing heart rate, blood pressure, and energy mobilization. Their production is tightly regulated by signals from the brain, ensuring the body maintains balance.
How Adrenal Incidentalomas Are Discovered
Adrenal incidentalomas are identified when a person undergoes an abdominal imaging study for conditions unrelated to the adrenal glands. Common scenarios include scans for persistent abdominal pain, kidney stones, or cancer staging. The term “incidentaloma” refers to masses found serendipitously, not those discovered as part of a work-up for known adrenal disease or widespread cancer.
The increased use and improved resolution of imaging technologies like CT and MRI have significantly increased these discoveries. For instance, adrenal masses are detected in about 3% of abdominal CT scans, with prevalence increasing with age.
Characterizing Adrenal Incidentalomas
Once an adrenal incidentaloma is discovered, medical professionals evaluate its characteristics to determine if it is hormonally active or potentially malignant. This assessment combines specialized imaging and biochemical tests. The goal is to differentiate between benign (non-cancerous) and malignant (cancerous) lesions, and to identify if the mass produces excess hormones.
Hormonal activity is assessed through blood and urine tests. For example, excess cortisol can lead to Cushing’s syndrome, while overproduction of aldosterone may cause primary hyperaldosteronism. Elevated adrenaline or noradrenaline suggests a pheochromocytoma, a tumor that can cause high blood pressure. Hormonally active tumors may require treatment regardless of their size.
The risk of malignancy is evaluated based on imaging features and size. Most adrenal incidentalomas are benign adenomas. However, larger masses carry a higher risk of malignancy; lesions smaller than 4 cm have a low risk, while those larger than 6 cm have a significantly increased risk of being cancerous. Imaging characteristics, such as density on unenhanced CT scans (values below 10 HU indicate a benign adenoma), homogeneity, and contrast wash-out patterns, also help distinguish between benign and potentially malignant lesions. In some cases, specialized imaging like PET scans can provide further insights into the metabolic activity of the mass.
Management and Monitoring
The management of an adrenal incidentaloma depends on its characterization: whether it is hormonally active and if there is concern for malignancy. For non-functional incidentalomas with benign imaging features, observation and regular monitoring are recommended. This involves periodic follow-up imaging, such as CT or MRI scans, every 6 to 12 months for a few years, to track any changes in size.
Hormonal tests are also repeated annually for several years to ensure the mass does not begin to produce excess hormones. Many incidentalomas remain stable and do not require intervention. However, if the incidentaloma significantly increases in size (e.g., growing by more than 20% or 5 millimeters in diameter) or develops signs of hormonal activity, further evaluation or intervention may be considered.
Surgical removal (adrenalectomy) is recommended in specific situations. This includes cases where the incidentaloma is hormonally active, to prevent complications from hormone overproduction. Surgery is also advised if imaging characteristics suggest a high risk of malignancy, especially for larger lesions or those with suspicious features. The decision for surgical intervention is made after a thorough assessment and often involves a multidisciplinary team.