Cystic and solid renal masses can be imaged with ultrasound, CT, and MRI, with contrast enhancement needed to optimize renal mass detection and characterization. Most very small renal masses cannot be characterized due to their size. Because the overwhelming majority of these are benign, follow-up is suggested only when these masses appear heterogeneous. CT and MRI are able to predict which cystic renal masses are most likely to be malignant. CT and MRI can identify macroscopic fat in the vast majority of angiomyolipomas, allowing for differentiation from other solid renal masses. Although some solid renal masses without macroscopic fat may contain distinct combinations of imaging features, there is much overlap, and biopsy will often be required for diagnosis. CT and MRI are accurate in staging renal cancers, predicting whether partial nephrectomy can be performed successfully, and for imaging patients after treatment. Unique patterns of metastatic disease response can be encountered after treatment of metastatic renal cancer with targeted chemotherapeutic agents. Radiologists must be aware of these patterns as well as of the imaging appearance of newly emerging treatment complications.
Copyright 2018, The Author(s).