I'm male 17 why has 1 of my testicle grown pea sized?

Here are some ...: Either age of 17 or 47, a pea-sized testicle could result from congenital (related with undescended testicle with orchiopexy), post-mumps orchitis since childhood, inadvertent severing testicular artery during inguinal hernia repair or varicocele correction, etc. So, a detailed Hx may help track down the cause for severely shrunk testis.