Orchitis

A 20-year-old man comes to his primary care physician for evaluation of scrotal fullness of several weeks duration.The patient endorses an associated dull, achy pain in his scrotum when standing for prolonged periods that is relieved with lying flat. There are no acute episodes of sudden pain. He has no significant past medical history. Vitals are within normal limits. Physical examination reveals a left-sided scrotal mass that feels like a “bag of worms'' and decompresses with recumbency. The right scrotum is unremarkable. The scrotum does not transilluminate. Which of the following is the most likely complication of this patient's disease if left untreated?