Case report: A small hyperechoic renal mass was detected in a 57 year old female. This renal mass was further characterized by the absence of peripheral or intratumoral vascularity using directional power Doppler (dpD); however, there were intralesion spots colored after Levovist (pattern 1, according to Jinzaki). By computer tomography (CT) scan, the renal mass was considered a benign lesion. Three months later, no changes were detected using ultrasonography (US), while there was evidence of a focal intra-lesion neovascular zone using dpD (pattern 1 of Jinzaki). Magnetic resonance imaging (MRI) did not display evidence for malignancy. After six months, the MRI considered the mass an angiomyolipoma (AML). However, a vascular pattern around and inside the mass (pattern 4 of Jinzaki) was evident by using US-dpD and a percutaneous renal biopsy revealed a renal cell carcinoma.
Conclusion: This case suggests that directional power Doppler is useful for the detection of small hyperechoic renal masses considered benign by both CT scan and MRI, since dpD allows for early detection of the onset and development of neo-vascular structures. Therefore, directional power Doppler sonography would be useful in the follow up of renal masses which mimic benign lesions.