Ultrasound revealed a hypoechoic heterogeneous parenchymal mass, measuring 4.5/3cm, located in the inferior third of the right kidney, with deformity of the renal contour (image 1). No abnormal lymph nodes were seen in the renal hilum. The renal vein and the inferior vena cava were patent on Doppler ultrasound. On color Doppler numerous vessels appeared along the periphery of the mass.
A hyperechoic, shadowing focus was seen in front of the spine, at the level of the renal hilum (image 2). On color Doppler a focal dilatation along the right renal artery was suggested (image 3). The left kidney was normal.
The US findings in renal cell carcinoma vary with the size of the lesion. Smaller lesions tend to be homogenous and hyperechoic. As the tumor enlarges it may become isoechoic and be detectable only through its mass effect causing distortion of the renal contour. Larger lesions tend to become heterogeneous and develop hypoechoic elements. Hemorrhage and necrosis within the lesion may give rise to cystic elements.
The peculiarity of our case consisted in the finding of a renal artery aneurysm (RAA) in association with renal cell carcinoma. The RAA was discovered incidentally in this patient and there is no known relationship between RCC and RAA.
Renal artery aneurysm (RAA) is a rare pathological entity. The incidence of renal artery aneurysms in the general population is unknown. Aneurysmal dilation of a renal artery is present when the diameter of that segment exceeds twice that of a normal-appearing artery. RAAs can be classified as extraparenchymal (saccular, fusiform, false/disecting) or intraparenchymal. [1,2]
True aneurysms of the renal artery are very uncommon, and while no single etiology can be forwarded to explain all aneurysms, most authors believe that a defect, perhaps congenital, exists in the vessel wall. When stressed by inflammation-from atherosclerosis, hypertension, or a vasculitis (e.g., polyarteritis nodosa), this results in progressive enlargement of the vessel. The association with atherosclerosis has been doubted by some with some authors believing that the rim calcifications seen with aneurysms, particularly in their later enlarged stages, may be a secondary event, rather than the primary causative factor. 
Most RAAs are asymptomatic, but some of the following clinical signs may appear: hypertension, flank pain, hematuria, obstruction of the collecting system, renal infarction or rupture. Our patient’s RAA was asymptomatic. [1, 2]
On ultrasound, a RAA appears as a rounded or oval anechoic zone, located in the renal sinus, anterior to the pelvis. Calcifications of various dimensions may be seen in the wall. At times, cardiac pulsation and hypoechoic parenchymatous areas in the lumen (partial thrombosis) may be observed. In some cases the communication with the renal artery or aorta is obvious. The diagnosis of certainty is determined by Doppler ultrasound, which shows turbulent arterial flow in the lumen.  In our case, the presence of RAA was suggested by the US findings but a CT scan was needed for confirmation.
Typical CT findings of RAA include a well-defined mass with wall calcifications and increased density after contrast enhancement, in the arterial phase.