Benign and Malignant Renal Disease

Abstract

AbstractImaging of renal disease encompasses a wide spectrum of benign, malignant, and non-neoplastic lesions. Focal renal masses (of benign and malignant origin) are the most frequent entities and the number of incidentally detected renal lesions is constantly increasing. Several imaging modalities are available to optimize characterization, staging, and treatment of cystic and solid renal masses. Cystic and solid renal masses can be imaged with ultrasound (US), computed tomography (CT), and magnetic resonance imaging (MRI), with contrast enhancement needed to optimize renal mass detection and characterization. Most very small renal masses of less than 1–1.5 cm cannot be characterized due to their size. Because most of these lesions are benign, follow-up is suggested only when these masses appear heterogeneous on imaging. CT, MRI, and contrast-enhanced US (CEUS) can predict which cystic renal masses are most likely to be malignant. CT and MRI can identify macroscopic fat in the vast majority of benign angiomyolipomas (AMLs), allowing for differentiation from other solid renal masses including renal cell cancer (RCC). Although some solid renal masses without macroscopic fat may contain distinct combinations of imaging features, there is much overlap and renal mass biopsy will often be required for definitive diagnosis as well as for patient risk stratification. Furthermore, CT and MRI are accurate in local staging of renal cancers, predicting whether partial nephrectomy or local ablation can be performed successfully, and for imaging of patients after treatment. Unique patterns of metastatic disease response can be encountered after the treatment of metastatic renal cancer with targeted chemotherapeutic agents. Radiologists must be aware of typical imaging features of cystic and solid renal masses, cancer mimics as well as response patterns and are key stakeholders within interdisciplinary treatment decisions to support the diagnostic workup and management of renal masses with emerging treatment options for RCC.