CT follow-up

• <6 mm, low risk: no routine follow-up.
• <6 mm, high risk: optional CT at 12 months.
• 6–8 mm: CT at 6–12 months, consider 18–24 months.
• >8 mm: CT at 3 months, PET/CT, or tissue sampling.

Source: Fleischner Society 2017

• Pure GGN <6 mm: no routine follow-up.
• Pure GGN ≥6 mm: CT at 6–12 months, then every 2 years up to 5 years.
• Part-solid ≥6 mm: CT at 3–6 months; persistent solid ≥6 mm → biopsy/resection.

Source: Fleischner Society 2017

• <10 HU on non-contrast: benign adenoma — no follow-up.
• Indeterminate (>10 HU): adrenal protocol CT or MRI in/out-of-phase.
• ≥4 cm or suspicious features: endocrine + surgical referral.

Source: ACR Incidental Adrenal Mass white paper

• Bosniak I–II: no follow-up.
• Bosniak IIF: CT/MRI 6 months, then annually for 5 years.
• Bosniak III–IV: urology referral, consider intervention.

Source: Bosniak 2019