There is a correlation between small scrotum and absent testicles. In addition to the corresponding condition, other factors can also cause the corresponding change, mainly including congenital development, acquired atrophy and testicular injury. 1. Absence of testicle: The main reasons for the absence of testicle in the scrotum include underdeveloped testicle and cryptorchidism, etc. The corresponding condition will cause one side of scrotum to be small. 2. Congenital development: It is only slightly small, not too abnormal, and is caused by congenital asymmetrical development. 3. Acquired atrophy: hormone level decreases with age, or the endocrine function is abnormal, which may cause hormone level to decrease and lead to testicular atrophy on one side. 4. Testicular injury: after trauma or infection, it will cause testicular injury, which will further lead to testicular atrophy. Smaller scrotum on one side may also be caused by other factors, if accompanied by coital status and ejaculation abnormalities, you need to consult a doctor for observation, and after diagnosing the cause of the disease, carry out standardized treatment under the guidance of the clinician, to avoid delays in the condition.