What is the appropriate CT imaging protocol for evaluating adrenal insufficiency?

CT Protocol for Adrenal Insufficiency

For evaluating primary adrenal insufficiency, obtain a standard non-contrast abdominal CT scan—a dedicated adrenal-specific protocol is not required. 1

Recommended CT Protocol

• Non-contrast CT is the preferred first-line imaging modality for assessing adrenal glands in suspected primary adrenal insufficiency. 1

• A standard abdominal CT protocol is sufficient; the three-phase dedicated adrenal protocol (non-contrast, venous phase at 60-70 seconds, and delayed phase at 15 minutes) used for characterizing adrenal masses is unnecessary when evaluating for adrenal insufficiency. 2, 1

• CT is recommended over MRI because it offers wider availability, shorter scan times, lower cost, and better patient tolerability. 2, 1

What the CT Should Assess

• Size and morphology of both adrenal glands: Look for atrophy (small, thin glands), which is highly characteristic of chronic adrenal insufficiency, particularly in autoimmune adrenalitis. 3

• Calcifications: Adrenal calcifications are frequently seen in tuberculous adrenalitis and are particularly common in patients over age 50 with Addison's disease. 4, 3

• Adrenal enlargement or masses: Bilateral adrenal masses may indicate hemorrhage, metastases, infiltrative disease (tuberculosis, histoplasmosis, sarcoidosis), or lymphoma. 4, 5

• Heterogeneity and hemorrhage: Acute bilateral adrenal hemorrhage appears as bilateral adrenal masses on CT and can cause acute adrenal insufficiency; follow-up CT shows diminution of masses with density changes consistent with resolving hematomas. 5

Technical Specifications

• Slice thickness: Use thin slices (2 mm) to optimize visualization of the adrenal glands. 3

• No contrast required: The non-contrast phase alone provides sufficient information to identify structural causes of primary adrenal insufficiency, including atrophy, calcification, hemorrhage, and masses. 1, 3

Clinical Context & Pitfalls

• CT is performed to determine the etiology of confirmed primary adrenal insufficiency, not to diagnose the insufficiency itself—diagnosis requires biochemical testing (ACTH stimulation test with peak cortisol <500 nmol/L). 1

• Order CT after autoimmune serology: First measure 21-hydroxylase autoantibodies; if negative, proceed with CT to evaluate for tuberculosis, malignancy, infiltrative disease, or hemorrhage. 1

• CT findings vary by etiology:

  • Autoimmune adrenalitis: bilateral adrenal atrophy with abnormal shape 3
  • Tuberculous adrenalitis: enlarged glands with calcifications 4
  • Acute hemorrhage: bilateral adrenal masses that resolve on follow-up 5
  • Metastatic disease: bilateral adrenal masses without calcification 6

• Do not confuse with adrenal mass characterization protocols: The dedicated three-phase adrenal washout protocol is designed to distinguish adenomas from other masses in patients with incidental adrenal lesions, not to evaluate adrenal insufficiency. 2, 7

• CT has high accuracy for detecting adrenal pathology: Historical studies demonstrate CT correctly identifies adrenal masses and accurately predicts presence or absence of adrenal neoplasms when both glands are adequately visualized. 6