Which benign fatty renal tumor is commonly found in the right kidney?

Angiomyolipoma is the correct choice as it is a common benign fatty tumor that primarily affects the kidneys, particularly the right kidney. It is composed of blood vessels, smooth muscle tissue, and fat cells. This unique composition is what distinguishes angiomyolipoma as a fatty tumor, and its occurrence in the right kidney is more frequent due to factors such as renal anatomy and blood supply.

Patients with angiomyolipoma may be asymptomatic, but in some cases, the tumor can cause symptoms such as pain or bleeding if it grows large enough or if there is a rupture. The presence of fat within the tumor represents its benign nature and is typically detected during ultrasound examinations, where it appears as a hyperechoic lesion.

Other conditions listed do not represent fatty renal tumors. Medullary sponge kidney is a developmental disorder characterized by cystic dilatation of the collecting tubules in one or both kidneys, and it does not involve fatty tissue. A duplex kidney refers to a duplication of the renal collecting system, which is an anatomical variation rather than a tumor, while renal cell carcinoma is a malignant tumor and not benign.