Eight-year-old boys with different sizes of testicles may be a normal phenomenon, but some pathological factors such as hiatal hernia, testicular syringomyelia or epididymitis may cause the two testicles to be different in size. 1. Normal human testicle size generally has a difference, a small one, a high one, if the difference is not big, generally do not need to worry, the reproductive function will not be affected. 2. Hiatal hernia: Hiatal hernia is usually manifested as a mass in the inguinal area that can be seen when standing or walking, protruding through the inguinal canal and descending into the scrotum, making the scrotum different in size from left to right. 3. Testicular syringomyelia: there is more fluid in the testicular syringomyelia capsule, forming a scrotal mass, presenting painless chronic enlargement, when the amount of fluid is large, the scrotum may feel distended and painful, falling or pulling sensation. 4. Epididymitis: it can be caused by the spread of urinary tract infections, inflammation can cause swelling of the epididymis, and epididymo-orchitis is formed when the testicles are involved, the scrotum on the side of the disease is obviously swollen, and the skin of the scrotum is hot, red and painful. In addition, eight-year-old boys testicle size may also be testicular tumors and other causes, if the boy’s two sides of the testicle size difference is large or accompanied by other discomforts, it is recommended to go to the hospital in a timely manner to consult a doctor, clear causes, targeted treatment.