Fig. 3

Renal masses that do not need to be followed. a Axial contrast-enhanced CT showing a right renal too small to characterize mass (TSTC) (arrow); the renal mass is 8 mm in size, and the CT slice thickness is 5 mm, making the renal mass size less than twice the reconstructed CT thickness (8 mm/10 mm). b Axial contrast-enhanced CT showing a hypodense left kidney lesion measuring 3 HU (less than 20 HU), which is likely a simple cyst (arrow). c Axial non-enhanced CT showing a hyperdense left kidney cyst with an attenuation value of 85 HU greater than 70 HU, consistent with a hemorrhagic cyst (arrow). d Contrast-enhanced US of a Bosniak I cystic lesion showing no wall thickening or septa (arrow). e Unenhanced (right) and contrast-enhanced (left) US of a renal Bosniak II cystic lesion with thin septa that did not enhance in the post-contrast study (arrows)