What is the next step in management for a patient with a 1.8 cm hypodense nodule in the right adrenal gland?

Management of a 1.8 cm Hypodense Adrenal Nodule (HU 40)

The next step in management for a patient with a 1.8 cm hypodense nodule (HU 40) in the right adrenal gland is to perform a complete hormonal evaluation including 1 mg overnight dexamethasone suppression test, plasma or 24-hour urinary metanephrines, and aldosterone-to-renin ratio if the patient has hypertension or hypokalemia. 1, 2

Rationale for Hormonal Evaluation

A complete hormonal workup is mandatory before any intervention for all adrenal nodules, regardless of size or imaging characteristics. This approach is essential because:

1. Functional status determines management: Even small nodules can be hormonally active and require surgical intervention
2. Safety considerations: Failing to identify a pheochromocytoma before intervention can lead to life-threatening complications 2
3. Clinical guideline consensus: All current guidelines recommend hormonal evaluation as the first step 1, 2

Specific Hormonal Tests Required

• Cortisol secretion: 1 mg overnight dexamethasone suppression test (preferred screening test) 1, 2

  • Cortisol <50 nmol/l (1.8 μg/dl): Excludes autonomous cortisol secretion
  • Cortisol 51-138 nmol/l (1.9-5.0 μg/dl): Possible cortisol secretion
  • Cortisol >138 nmol/l (>5.0 μg/dl): Evidence of autonomous cortisol secretion

• Pheochromocytoma screening: Plasma or 24-hour urinary metanephrines 1, 2

  • Required for nodules with HU >10 on non-contrast CT (this patient has HU 40)

• Aldosterone evaluation: Aldosterone-to-renin ratio 1, 2

  • Indicated if patient has hypertension and/or hypokalemia

Imaging Considerations

The nodule in question has several characteristics that warrant attention:

• Size: 1.8 cm (less than the 4 cm threshold for automatic surgical consideration)
• Density: HU 40 (significantly above the HU 10 threshold that would indicate a benign lesion)

Since this is an indeterminate adrenal mass (HU >10), additional imaging may be considered after hormonal evaluation:

• Second-line imaging options: 1
  • Washout CT protocol
  • Chemical-shift MRI

However, recent evidence suggests washout CT may have limited utility in patients without known malignancy, with a study showing suboptimal performance for characterizing nodules as benign 3.

Management Algorithm Based on Evaluation Results

1. If hormonally active:

   • Cortisol-secreting adenoma: Consider adrenalectomy, especially if clinically apparent Cushing's syndrome or progressive metabolic comorbidities 1
   • Aldosterone-secreting adenoma: Adrenalectomy (with adrenal vein sampling recommended prior to surgery) 1
   • Pheochromocytoma: Adrenalectomy (with preoperative alpha-blocker treatment) 1, 2

2. If hormonally inactive:

   • For this 1.8 cm nodule with HU 40:
     • Consider second-line imaging (washout CT or chemical-shift MRI) 1
     • If imaging remains indeterminate, shared decision-making between patient and clinician regarding management options (repeat imaging in 3-6 months versus surgical resection) 1

Important Considerations

• Adrenal biopsy: Not recommended routinely for adrenal incidentalomas 1, 2
• Malignancy risk: Low for nodules <4 cm without history of malignancy (only 0.3% in one study) 3
• Follow-up: If determined to be a benign non-functional adenoma <4 cm, no further follow-up imaging or functional testing is required 1
• Surgical approach: If surgery is indicated, minimally-invasive surgery should be performed when feasible 1

Remember that a multidisciplinary approach involving endocrinologists, surgeons, and radiologists is recommended when imaging is not consistent with a benign lesion or when there is evidence of hormone hypersecretion 2.