The incidental renal mass.

Incidental renal masses are extremely common. Although most represent benign renal cysts, not all incidental renal masses are benign. Most renal cell carcinomas are discovered incidentally when an imaging examination is performed to evaluate a nonrenal complaint. Therefore, differentiating incidental benign renal masses from those that are potentially malignant is important. There are well-established, time-tested, image-based criteria that can be used to diagnose most renal masses definitively. However, some renal masses remain indeterminate even after a thorough evaluation with imaging. This article discusses the evaluation, diagnosis, and treatment options of the incidental renal mass.