In case of unilateral testicular pain, it is recommended to visit a hospital to clarify the specific cause.1. Unilateral orchitis or epididymitis may cause acute swelling of the testicles and epididymis with inflammatory reaction. The skin of the scrotum appears red and swollen, painful when touched, or the testicles and epididymis are closely adherent and the boundaries are unclear. Routine blood tests and ultrasound examination of the testes and epididymis are needed to rule out the presence of orchitis or epididymitis. 2. Testicular torsion, a urological emergency. The position of the testicle moves upward in appearance, and the position of the testicle is more fixed when it is pushed by hand, and it is not easy to be pushed, and it is accompanied by obvious pain. The pain increases progressively over time, and in severe cases, there may be small abdominal or lower back pain. If the testicular torsion is diagnosed, surgery is recommended within 6 hours to restore the torsion and improve the blood flow to the testicle to avoid ischemic necrosis.