The pediatric testis should be symmetrically positioned and equal in size on both sides, which is the normal morphological structure. If both sides are not equal and not equal in size, pathological diseases are considered. Possible causes: 1. Testicular syringomyelia. When there is syringomyelia in the testicles, there can be enlargement of the scrotum on the affected side, and the appearance of one testicle is large and one testicle is small, and there is usually no painful symptom when touched by hand. It is recommended to perform ultrasound examination of the testicles to determine whether there is syringomyelia, and if there is syringomyelia, surgery is needed if necessary. 2. Inflammation of the testicles. When the infection can appear on the infected side of the testicle enlargement, and accompanied by testicular pain symptoms, the pain is more obvious when touching with hands or walking. In this case, combined with the symptoms and routine urine examination, ultrasound examination of scrotum and testicles, it can be determined whether there is infection, if there is infection, it is recommended to give further anti-infection treatment. 3, unilateral testicular atrophy. The testicle on the atrophied side can appear smaller in size. This condition can occur after testicular torsion, local atrophy due to ischemia, usually with a history of acute pain, or blood damage to the unilateral testicle after surgery, and post-operative testicular disequilibrium on both sides, with the testicle on the ischemic side being relatively smaller in size. This situation needs to be further judged based on the child’s medical history and physical examination. Scrotal ultrasound and color Doppler examination of the spermatic cord can be done to understand the actual volume of the testes and to see if there is ischemic atrophy and other conditions.