Makindo Medical Notes

🧩 Angiomyolipoma (AML) is a benign hamartomatous tumour of the kidney, made up of fat, smooth muscle, and blood vessels. ⚠️ While usually asymptomatic, large AMLs can rupture and bleed (Wunderlich syndrome).

📖 About

• Benign renal parenchymal tumour – often incidental finding on imaging.
• Classic association with Tuberous Sclerosis Complex (TSC) 🧠.
• Bleeding risk rises when size >4 cm or when vascular components are prominent.

🧬 Aetiology

• Composed of a mixture of adipose tissue, smooth muscle, and thick-walled vessels.
• Hamartomatous origin (disorganised growth of normal elements).
• Malignant transformation is rare but has been described in atypical cases.

👩‍⚕️ Clinical Features

• More common in women, peak in 4th–5th decade.
• Often asymptomatic – discovered on ultrasound/CT for another reason.
• When symptomatic:
  • Flank or abdominal pain.
  • Palpable mass.
  • Microscopic or macroscopic haematuria 🚨.
• Large lesions can rupture → retroperitoneal haemorrhage with hypotension, shock (Wunderlich syndrome) 💉.

🧪 Investigations

• CT Abdomen: ✅ Diagnostic test of choice – shows fat attenuation within the mass (classic hallmark).
• Ultrasound: Hyperechoic lesion due to fat content (but not specific).
• MRI: Helpful if CT is inconclusive or to differentiate from renal cell carcinoma.
• TSC screening: If AML is multiple/bilateral, consider workup for tuberous sclerosis.

🩺 Management

• 🎯 Conservative: Small (<4 cm), asymptomatic → monitor with regular imaging.
• 💉 Embolisation: Minimally invasive, first-line for bleeding AMLs or symptomatic cases.
• 🔪 Surgery:
  • Partial nephrectomy if localised and symptomatic.
  • Radical nephrectomy only if uncontrollable bleeding or malignancy can’t be excluded.
• 📏 Size threshold: >4 cm = higher risk of rupture → consider prophylactic intervention.

🌟 Clinical Pearls

• Think “fat in the kidney” on CT → Angiomyolipoma until proven otherwise.
• Multiple AMLs in a young patient → screen for TSC (look for seizures, skin lesions, cognitive impairment).
• New targeted therapy (mTOR inhibitors like everolimus) can shrink AMLs in TSC patients.

📚 References

• UpToDate: Renal Angiomyolipoma
• AJR Review on Imaging of AML