Adrenal Nodules Management Guidelines

Size Thresholds for No Further Workup

Adrenal nodules less than 40 mm that are benign-appearing on imaging and non-functional do not require further follow-up imaging or functional testing, as recommended by the American Urological Association (strong recommendation, moderate quality evidence) 1, 2, 3
Benign non-functional adenomas <40 mm require no further follow-up imaging or functional testing (strong recommendation, moderate quality evidence) 1, 2, 3
Myelolipomas and other small masses containing macroscopic fat detected on initial workup do not require further follow-up regardless of exact size if clearly identified 1, 2

Before concluding no workup is needed, the nodule must demonstrate benign imaging features, including homogeneous appearance with well-defined margins 4
If HU >10, second-line imaging with washout CT or chemical shift MRI must confirm benign characteristics before observation 1

All adrenal incidentalomas, regardless of size or benign appearance, require initial hormonal evaluation, including plasma aldosterone and renin ratio if hypertensive or hypokalemic 4
Approximately 5% of radiologically benign incidentalomas have subclinical hormone production that requires treatment 6, 4

For nodules ≥40 mm, even if radiologically benign, repeat imaging in 6-12 months is recommended, as most surgically resected pheochromocytomas and adrenocortical carcinomas were >40 mm at diagnosis 1, 2, 3
For nodules 30-50 mm, require second-line imaging if not already performed, as malignancy risk increases in this size range 5, 6
For nodules >50 mm, surgical resection should be strongly considered due to significantly elevated malignancy risk (21.1% for nodules ≥40 mm) 6

Patients with history of extra-adrenal malignancy require closer evaluation, as metastatic risk is 25-72% depending on primary tumor, and the 40 mm threshold does not apply in this population 6, 4
Young adults, children, and pregnant patients require expedited evaluation, as adrenal lesions are more likely malignant, and consider low-dose CT or chemical shift MRI for radiation safety 1, 2

If follow-up imaging is performed, growth <3 mm/year requires no further imaging or functional testing, while growth >5 mm/year requires consideration of adrenalectomy after repeating functional workup 1, 2, 3

Failing to perform initial hormonal evaluation on radiologically benign lesions, as subclinical hormone excess occurs in 5% of incidentalomas and requires treatment 6, 4
Performing adrenal biopsy routinely, which should be reserved only for cases where noninvasive techniques are equivocal with high suspicion for metastatic disease 6, 4