Current patterns of imaging utilization lead to frequent serendipitous discovery of renal lesions. Today, the majority of solid renal masses that are ultimately proved to be renal cell carcinomas were incidental findings on imaging studies performed for non-urinary tract symptoms. While earlier discovery has led to treatment of smaller and earlier-stage malignancies, the percentage of benign lesions discovered has also increased. A strategy for characterization of solid masses in adults based on the lesion's growth pattern, the "ball" versus the "bean," is presented. Common and uncommon renal masses, in concert with clinical and other imaging clues, are reviewed within the context of a renal ball or bean.
(c) RSNA, 2008.