The two sides of testicles are not the same size, the possible reasons are: 1, testicular syringomyelia, the affected side of the testicle relative to the healthy side of the testicle is larger in size, then you need to carry out ultrasound examination of the scrotum to confirm the presence of syringomyelia. If there is syringomyelia, oral medication or surgical treatment is needed, then both sides can be equal and symmetrical.2. Testicular tumors on the affected side, such as testicular cancer, can appear on both sides of the testicles are not equal in size. Usually, the size of testis on the affected side is larger, and the testis on the healthy side is normal. In addition to testicular enlargement, testicular tumor may cause scrotal swelling, pain and discomfort, and the density of testicle on the diseased side is increased, which is like a rock or a stone, heavy feeling.3. Acute epididymitis or orchitis, in the acute stage, the testicle or epididymis may be edema and enlarged. At this time, the size of bilateral testicles is not equal, in addition to the size of the volume is not equal, there may also be pain when touching the testicles or pain in the scrotum when walking. It is recommended to perform urine routine and scrotal ultrasound examination to exclude whether there is inflammation, anti-inflammatory treatment, after the inflammation subsides, bilateral testicles can be restored to the state of equal size.