Surveillance Protocol for Angiomyolipomas (AMLs)

Surveillance Recommendations Based on AML Size

For AMLs 2-3.9 cm, monitoring with ultrasound every 3 years is recommended, as per the American College of Radiology 2
For AMLs 3-3.9 cm that are inadequately visualized by ultrasound, CT or MRI surveillance is recommended, according to the European Society of Nephrology 3
AMLs 4-4.9 cm should be monitored every 6-12 months with MRI or CT, due to increased risk of hemorrhage, as suggested by the European Respiratory Society 1
AMLs ≥5 cm should be monitored every 6 months with MRI or CT due to higher risk of hemorrhage, as recommended by the European Respiratory Society 1

MRI is the preferred modality for detecting and monitoring kidney lesions, especially for long-term surveillance due to lack of radiation exposure, as stated by the European Society of Nephrology 3
Ultrasound performed by an expert radiologist is an acceptable alternative for smaller lesions, particularly in children, according to the European Society of Nephrology 3
CT with contrast is appropriate when MRI is contraindicated or unavailable, providing excellent visualization of the lesion and potential aneurysms, as recommended by the European Society of Nephrology 3
The same imaging modality should be used consistently for follow-up to ensure accurate assessment of growth, as suggested by the European Society of Nephrology 3

Presence of aneurysms within the AML requires more intensive surveillance, as recommended by the European Respiratory Society 1

For AMLs ≥4 cm with high-risk features, consider prophylactic embolization as first-line therapy, as suggested by the European Respiratory Society 1
For TSC-associated AMLs ≥4 cm, consider mTOR inhibitors (everolimus 5-10 mg daily for adults) with imaging follow-up every 3 months initially, as recommended by the European Society of Nephrology [4] [5]
If using intermittent mTOR inhibitor therapy, restart treatment if AML volume increases to >70% of pre-treatment size, as suggested by the European Society of Nephrology 4
For bleeding AMLs, urgent embolization is the first-line treatment regardless of size, as recommended by the European Respiratory Society 1

Using different imaging modalities for sequential measurements, leading to inconsistent size assessments, is a common pitfall, as noted by the European Society of Nephrology 3
Overlooking fat-poor AMLs that may be difficult to distinguish from renal cell carcinoma on ultrasound is a common pitfall, as warned by the European Society of Nephrology 3