Adrenal Incidentaloma

• Definition: >1cm mass found incidentally on imaging - prevalence is 5%

• First step is to determine likelihood of malignancy based on imaging characteristics
  • Size >4 cm and high attenuation (>10 Hounsfield units) raises concern for malignancy
• For radiographically benign mass, next step is to determine whether mass is functional, as vast majority of benign adenomas are non-functioning
  • All patients should be evaluted for Cushing's syndrome and pheochromocytoma, and hypertensive patients for hyperaldosteronism
    • Cushing's syndrome:
      • Signs: central obesity, suproclavicular fat pad, striae, diabetes, thin skin, hypertension, plethora
      • Diagnosis: low-dose dexamethasone suppression test, midnight salivary cortisol (to evaluate for diurnal variation), 24h urine cortisol
    • Conn's syndrome:
      • Signs: hypertension, hypokalemia
      • Diagnosis: Aldosterone to renin ratio, with value greater than 20 suggesting diagnosis
        • Should be done in early morning, and when patient is ambulatory
        • Cannot be done if patient is on aldosterone antagonist
        • If patient is on ACEi/ARB, renin typically elevated, so low ratio may be inaccurate, but high ratio (i.e. low renin) strongly suggests diagnosis
    • Pheochromocytoma:
      • Symptoms: palpitations, headache, diaphoresis
      • Signs: hypertension, paradoxical hypotension
      • Diagnosis: 24h urine catechloamines/metanephrines (more specific), plasma metanephrines (more sensitive)
        • Choice of test depends on pretest probability

(Christopher Woo MD, 8/14/10)