Background: This is a study using Evidence Based Practice (EBP) technique to evaluate if non-calcified renal lesions detected with ultrasound, suspected to represent an angiomyolipoma (AML), need a CT to rule out a renal cell carcinoma (RCC).
Methods: The secondary and primary literature were searched for all relevant information. This was appraised for validity and strength. The results from the papers with the highest level of evidence were grouped together and analyzed.
Results: Three papers in the primary literature constituted the highest level of evidence. In total these three papers examined 220 lesions. The prevalence of AML was 45% in this sample. Overall, hyperechoic non-calcified renal lesions had a sensitivity of 0.99 (95% confidence interval (CI) 0.97-1.00), a specificity of 0.43 (95% CI 0.34-0.51), a positive predictive value (PPV) of 0.58 and a negative predictive value (NPV) of 0.98 for AMLs. 57.4% of RCCs were hyperechoic to renal parenchyma. Two of the studies found that posterior acoustic shadowing had a sensitivity of 0.34 (95% CI 0.40-0.56) and a specificity of 1.0 (95% CI 1.0-1.0) for AML.
Conclusions: From the surprisingly limited evidence available in the literature, it must be concluded that all non-calcified echogenic renal lesions detected with ultrasound need a CT to rule out an RCC.