Renal angiomyolipoma: optimal treatment based on size and symptoms

The natural history of renal angiomyolipoma is not well delineated. Current management options include observation, embolization, and partial or total nephrectomy. Recommendations for treatment are usually based on the patient's symptoms or the size of the lesion. In an effort to help define the optimal treatment of renal angiomyolipomas, we reviewed our experience over the last 10 years with these tumors. We performed a retrospective study of 37 patients (48 renal units) diagnosed with renal angiomyolipoma over a ten year period at our medical center (mean follow-up 40 months, range 1 month-12 years). Lesions were classified as small (< 4 cm), medium (4-8 cm) or large (> 8 cm) based on the single largest lesion in each kidney. The relationship between the size, symptoms and treatment was reviewed. Patients were also analyzed with regard to the diagnosis of tuberous sclerosis. Our findings indicate renal angiomyolipomas less than 4 cm (21/37 patients) tend to be asymptomatic and generally do not require intervention. Angiomyolipomas greater than 8 cm were responsible for significant morbidity and generally require treatment (5/6). Patients with tuberous sclerosis made up one half (3/6) of the large lesions. Medium-sized lesions had a less predictable natural history, with 54% (7/13) requiring intervention to treat hemorrhagic complications. Small asymptomatic lesions (< 4 cm) tend to remain stable but should be periodically evaluated. Medium-sized lesions (4-8 cm) have the most variable behavior. These lesions should be followed closely with serial imaging studies, and if significant changes in size or symptoms are noted, or the patient is at risk for flank trauma, elective intervention should be initiated promptly to increase the chances of renal salvage. Large asymptomatic angiomyolipomas (> 8 cm) will most likely become symptomatic and should be treated electively prior to the development of symptoms and potential complications.