Figure 5a. Residual or recurrent RCC of the right kidney after cryoablation in a patient who had undergone right partial nephrectomy for RCC 4 years earlier. (a) Axial contrast-enhanced T1-weighted MR image shows an intensely enhancing mass (arrow) in the right kidney. Cryoablation was performed. (b) CT scan obtained during cryoablation performed with the patient prone demonstrates the cryoprobe tip in the tumor surrounded by ice ball formation. (c) Arterial phase CT scan obtained 4 months after cryoablation shows an area of hypoattenuation representing the ablated lesion, along with a curvilinear hyperattenuating area in the perinephric fat surrounding the lesion. A small nodular enhancing focus (arrow) is seen in the right kidney at the periphery of the ablated lesion. (d) Arterial phase CT scan obtained 12 months after cryoablation shows an interval increase in the size of the nodular enhancing focus (arrow), a finding that indicates viable tumor. (e) Excretory phase CT scan shows washout of contrast material from the enhancing nodule (arrow). Excreted contrast material is seen in the upper pole calix (arrowhead).