What are the CT and MRI features of metastatic disease to the kidneys?
Metastatic disease to the kidney is the most common malignant tumor of the kidney, is 4-fold more common than RCC in patients with a history of malignancy, and most often occurs in the setting of lung cancer, breast cancer, gastrointestinal malignancies, and melanoma.
On CT and MRI, renal metastases will vary in their attenuation, signal intensity, and enhancement properties depending on their tissue composition, but they are often heterogeneous in appearance, usually restrict diffusion, and are usually hypoenhancing relative to renal parenchyma. The suspicion for metastatic disease is greater when the lesions are multifocal and bilateral, are heterogeneous but with similar enhancement patterns, have an infiltrative growth pattern, grow over time, or are seen in the presence of metastatic disease to other sites of the body. When necessary, percutaneous biopsy is performed to distinguish between renal metastatic disease and RCC.