Orchitis

A 29-year-old man comes to the clinic because of testicular pain that has worsened in the last 24 hours. He is a refugee who recently immigrated to the United States, and does not have a medical record. He has been in good health except for a fever that began last week. Physical examination shows unilateral scrotal swelling and erythema that is painful upon palpation of the testicle and epididymis. He has bilateral swelling of his face over the angle of each mandible. His temperature is 39ºC (102.2ºF), pulse is 82/min, respirations are 15/min, and blood pressure is 115/80 mm Hg. Which of the following is the most common additional complication of this patient's condition?