What are the radiographic findings on CT (computed tomography) scans in patients with adrenal insufficiency?

CT Findings in Adrenal Insufficiency

CT imaging in patients with adrenal insufficiency typically shows adrenal gland atrophy, abnormal adrenal shape, and calcifications, particularly in autoimmune cases. 1

Primary Adrenal Insufficiency CT Findings

Common Radiographic Findings

• Adrenal atrophy: Present in approximately 87% of patients with chronic adrenal insufficiency 1
• Abnormal adrenal shape: Seen in about 70% of patients 1
• Adrenal calcifications: Found in approximately 50% of patients, more common in those over 50 years of age 1

Etiology-Specific Findings

Autoimmune Adrenal Insufficiency

• High occurrence of adrenal gland atrophy 1
• Small, shrunken glands
• May show normal appearance in early stages of disease

Adrenal Hemorrhage

• Enlarged adrenal glands
• Periadrenal fat stranding (93% of cases) 2
• Focal hematoma (30% of cases) 2
• Indistinct adrenal gland (27% of cases) 2
• Retroperitoneal hemorrhage (22% of cases) 2
• Thickened diaphragmatic crura (10% of cases) 2

Pre-Hemorrhagic Changes

• Adrenal gland thickening
• Periadrenal fat stranding
• These findings may precede frank adrenal hemorrhage and could indicate impending adrenal insufficiency 3

Adrenal Ischemia

• "Capsular sign" - peripheral subtle hyperdense line around a hypodense enlarged adrenal gland
• Highly specific (100%) for acute adrenal ischemia 4
• May be associated with adrenal vein thrombosis

Diagnostic Approach

When to Consider Adrenal Insufficiency

• Unexplained collapse, hypotension, vomiting, or diarrhea 5
• Hyperpigmentation, hyponatremia, hyperkalaemia, acidosis, and hypoglycemia increase clinical suspicion 5

Recommended Imaging Protocol

• Non-contrast CT is the first-line imaging modality 6
• Assess for:
  • Adrenal size and shape
  • Presence of calcifications
  • Periadrenal fat stranding
  • Signs of hemorrhage or ischemia

Laboratory Correlation

• Paired measurement of serum cortisol and plasma ACTH is the diagnostic test for primary adrenal insufficiency 5
• Serum cortisol <250 nmol/L and increased ACTH in acute illness is diagnostic 5

Management Implications

Etiologic Diagnosis

• If 21-hydroxylase autoantibodies are negative, CT imaging is recommended 5
• In male patients with negative antibodies, very long-chain fatty acids should be checked for adrenoleukodystrophy 5

Acute Adrenal Crisis

• Treatment should never be delayed by diagnostic procedures 5
• Immediate administration of IV or IM hydrocortisone (100 mg followed by 100 mg every 6-8 hours) 5
• Isotonic sodium chloride solution at an initial rate of 1 L/hour until hemodynamic improvement 5

Important Considerations

Pitfalls in Interpretation

• Normal CT findings do not exclude early adrenal insufficiency
• Adrenal enlargement may be seen in acute adrenal insufficiency before atrophy develops
• Bilateral adrenal hemorrhage can lead to life-threatening adrenal insufficiency and requires prompt recognition 3

Follow-up Recommendations

• Patients with adrenal insufficiency should be reviewed at least annually 5
• Assessment should include health and well-being, weight, blood pressure, and serum electrolytes 5
• Monitoring for development of new autoimmune disorders, particularly hypothyroidism, is worthwhile 5

By recognizing these CT findings early, clinicians can initiate appropriate treatment to prevent morbidity and mortality associated with adrenal insufficiency.