On the left is a normal testis. On the right is a testis that has undergone atrophy. Bilateral atrophy may occur with a variety of conditions including chronic alcoholism, hypopituitarism, atherosclerosis, chemotherapy or radiation, and severe prolonged illness. A cryptorchid testis will also be atrophic. Inflammation may lead to atrophy. Mumps virus infection, the most common cause for orchitis, usually has a patchy pattern of testicular involvement that does not lead to sterility.

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