What are the causes of adrenal calcifications?

Causes of Adrenal Calcifications

Adrenal calcifications are most commonly idiopathic (72% of cases), followed by adrenal tumors (21%), hemorrhage (5%), and infiltrative diseases (1%). 1

Primary Etiologic Categories

Idiopathic Calcifications

• The majority of adrenal calcifications have no identifiable cause, representing approximately 72% of all cases in adults 1
• These are typically discovered incidentally on imaging (87% of cases) 1
• Most present as unilateral (94%), punctate (58%) or coarse (30%) calcifications 1
• Often attributed to undetected prior adrenal hemorrhage, particularly neonatal adrenal distress 2

Adrenal Tumors (21% of cases)

Benign tumors (81% of calcified tumors):

• Adrenal adenomas are the most common calcified tumor (69% of benign calcified tumors) 1
• Adrenal cysts show characteristic peripheral curvilinear calcification pattern 3
• Pheochromocytomas can calcify, though calcifications may indicate parenchymal degeneration 4
• Myelolipomas (uptake by myeloid tissue component) 4

Malignant tumors (18% of calcified tumors):

• Adrenal metastases are the most common calcified malignancy (67% of malignant calcified lesions) 1
• Adrenal carcinoma (typically >4 cm with irregular margins and heterogeneous appearance) 4
• Neuroblastoma (most common calcified adrenal mass in children) 3

Hemorrhage (5% of cases)

• Prior adrenal hemorrhage, often from neonatal period 1, 2
• Birth trauma (macrosomia, clavicle fracture) may cause undetected neonatal adrenal hemorrhage 2
• Acute adrenal hemorrhage visible on CT 5

Infiltrative/Infectious Diseases (1% of cases)

• Tuberculosis (requires testing in 21OH-Ab negative patients) 5
• Histoplasmosis 3
• HIV-related infections 5
• Other fungal infections 5

Diagnostic Approach Algorithm

Step 1: Assess Clinical Context

• Determine if patient has symptoms of adrenal dysfunction (hypercortisolism, hyperaldosteronism, or adrenal insufficiency) 4
• Most calcifications are incidental findings in asymptomatic patients 1

Step 2: Characterize Calcification Pattern on CT

• Peripheral curvilinear calcification strongly suggests adrenal cyst 3
• Punctate or coarse calcification is nonspecific 1
• Rim-like calcification (3% of cases) 1
• Linear/curvilinear pattern (9% of cases) 1

Step 3: Evaluate for Associated Mass

• Measure size: masses >4 cm with irregular margins suggest carcinoma 4
• Assess Hounsfield units on unenhanced CT (>10 HU suggests malignancy) 4
• Check enhancement washout at 15 minutes (>60% suggests benign) 4
• Note: Calcification without mass may still represent neuroblastoma elsewhere 6

Step 4: If Primary Adrenal Insufficiency Present

• Measure 21-hydroxylase autoantibodies first (accounts for 85% of PAI cases) 5
• If 21OH-Ab negative, perform CT to identify tumors, masses, calcifications, or hemorrhage 5
• Test for infectious causes: tuberculosis, HIV, fungal infections 5
• Consider genetic causes if other etiologies excluded 5

Step 5: Assess Bilaterality

• Bilateral calcifications (6% of cases) suggest systemic process: infectious disease, hemorrhage, or autoimmune adrenalitis 1
• Unilateral calcifications (94% of cases) more likely idiopathic or tumor-related 1

Critical Pitfalls to Avoid

• Do not assume all adrenal calcifications without mass are benign old hemorrhages—neuroblastoma can present with calcification before primary mass is evident 6
• In children, neuroblastoma is the most common calcified adrenal mass and requires immediate oncologic evaluation 3
• Calcification pattern alone cannot definitively distinguish benign from malignant lesions—must correlate with size, enhancement, margins, and clinical features 7, 3
• Less than 20% of calcified adrenal tumors are malignant or pheochromocytomas, but these require surgical intervention 1
• In young females with calcifications and adrenal insufficiency, never delay measuring 21OH-Ab as first-line test 5