A 65-year-old man with no notable medical history presented to the urology clinic with swelling in the area of the left testicle that had started 4 weeks earlier. Examination of the scrotum revealed an enlarged varicose vein along the left spermatic cord (Panel A, arrows), and abdominal palpation revealed a mass in the right flank. Computed tomography of the abdomen and pelvis revealed multiple bilateral renal tumors (Panel B, arrows), with the largest tumor located in the left kidney. Open radical nephrectomy of the left kidney was performed, and the results confirmed the diagnosis of renal-cell carcinoma. One week later, the varicocele disappeared. A varicocele is a dilatation of the pampiniform plexus of the spermatic cord; this network of veins is dependent on the spermatic vein. Varicocele occurs more commonly on the left side because the spermatic vein opens at a sharp angle into the left renal vein, whereas the right spermatic vein opens into the larger inferior vena cava. An acute nontraumatic varicocele, especially on the left side, may indicate the presence of a retroperitoneal mass.