When there is pain in one testicle, it is recommended to go to the hospital for relevant examinations to clarify the possible causes. First, whether testicular inflammation or epididymitis occurs, when inflammation occurs, pain in one side of the testicle can occur. It is usually accompanied by swelling of the testicle or epididymis. When the physical examination is touched with the hand, a significantly swollen testicle can be felt, accompanied by pain. The inflammatory reactions such as redness and swelling of the scrotal skin can be seen on the appearance. Ultrasound examination and routine blood tests are needed to further confirm the diagnosis. Second, if unilateral testicular torsion occurs, severe pain can also occur, often with a sharp onset and progressive increase in pain. During physical examination, the testicle position is fixed, not easy to push by hand, and the pain is obvious when touched, it is recommended to perform ultrasound examination of the testicle and spermatic cord to understand whether there is torsion. Thirdly, when there are varicocele and large amount of testicular sphincter effusion, chronic pain can also appear. The appearance can be seen as redness and swelling of the scrotum or an increase in the size of the testicles, or an increase in the contents of the scrotum, etc. Ultrasound examination of the scrotum is needed to confirm the diagnosis.