What is the recommended management for a patient with presumed angiomyolipomas (AML) of the kidneys?

Management of Presumed Renal Angiomyolipomas (AMLs)

For small, asymptomatic renal angiomyolipomas like those described in the ultrasound report, follow-up imaging with ultrasound in 6-12 months and then annually for 5 years is the recommended management approach. 1

Surveillance Recommendations Based on AML Size

• Small AMLs (<4 cm) detected incidentally should be followed conservatively with ultrasound every 6-12 months initially, as they show low risk of complications during long-term follow-up 2
• For AMLs 2-3.9 cm (like those described in the report), monitoring with ultrasound every 1-3 years is appropriate after initial follow-up 1
• If ultrasound visualization is inadequate, CT or MRI surveillance should be considered 1
• The same imaging modality should be used consistently for follow-up to ensure accurate assessment of growth 1

Risk Assessment and Management Algorithm

Low-Risk AMLs (Current Case)

• Small (<4 cm) 3
• No symptoms 3
• No aneurysms identified 3
• Management: Active surveillance with imaging follow-up 3, 1

High-Risk AMLs

• Size ≥4 cm 3, 1
• Presence of intratumoral aneurysms ≥5 mm 3, 1
• Symptomatic presentation (pain, bleeding) 3
• Management: Consider intervention with either:
  • Embolization (first-line therapy for bleeding AMLs) 3
  • mTOR inhibitors for TSC-associated AMLs 3
  • Nephron-sparing surgery when malignancy cannot be excluded 3, 1

Important Considerations

• Even small AMLs with rich vascular components can rarely rupture and cause life-threatening hemorrhage, particularly those located at the kidney surface 4
• Fat-poor AMLs may be difficult to distinguish from renal cell carcinoma on ultrasound, requiring additional imaging or follow-up 1, 5
• While most AMLs are benign, rare variants such as epithelioid angiomyolipoma can be locally aggressive 6
• If AMLs grow significantly during follow-up, reassessment of management strategy is warranted 2

Special Considerations for TSC-Associated AMLs

• For TSC-associated AMLs ≥4 cm, mTOR inhibitors (everolimus or sirolimus) should be considered 3
• mTOR inhibition therapy should be continued for a minimum of 12 months before assessing response 3
• If using mTOR inhibitors, monitoring should continue as discontinuation may lead to regrowth 3

Pitfalls to Avoid

• Using different imaging modalities for sequential measurements, leading to inconsistent size assessments 1
• Overlooking fat-poor AMLs that may be difficult to distinguish from renal cell carcinoma 1, 5
• Assuming all small AMLs are completely benign without appropriate follow-up, as rare cases of rupture in small AMLs have been reported 4

In this specific case with small, presumed AMLs (0.6 cm in left kidney and 5 mm in right kidney), the recommended 6-12 month initial follow-up ultrasound and then annual imaging for 5 years is appropriate and aligns with current guidelines 1, 2.