Juxtaglomerular Tumor (Reninoma). Juxtaglomerular tumors are rare, benign, renin-secreting masses derived from the juxtaglomerular apparatus. The classic presentation is a young patient (<25 years) with headache and hypertension who is found to have elevated serum renin and aldosterone concentrations and a low serum potassium concentration. Most tumors are unilateral, solitary, and relatively small (2 to 3 cm). Treatment consists of surgical removal, preferably with nephron-sparing surgery. Grossly, these tumors are well-encapsulated, with tan to yellow solid cut surfaces. Microscopically, the appearance is quite variable, with many tumors showing sheets of uniform round cells.

Renal Hemangioma. Renal hemangiomas are rare benign lesions that may cause either microscopic or gross hematuria. Most lesions are small and cannot be visualized using routine axial imaging of the kidney. Historically, arteriography was the most sensitive imaging modality; however, most renal hemangiomas are now diagnosed using cystoscopy, in which patients are noted to have unilateral hematuria (i.e., gross blood emerging from only one ureteric orifice). Most hemangiomas are located at the tip of a papilla and can range in size from pinpoint to several centimeters in diameter. In the past these masses were treated with nephrectomy or embolization; at present, however, treatment is usually electrocautery or laser ureteroscopic ablation.