In our daily clinical work, we always come across some parents who are in a hurry to consult the doctor: My child’s scrotum is not the same size on both sides, and I can’t even feel the “balls”, what should I do? So, what can be “packed” in the scrotum of a boy on both sides? The normal boy’s scrotum contains mainly testicles, epididymis and vas deferens. In addition, there can be “foreign objects” under abnormal conditions, such as intestinal tubes and intra-abdominal fluids, etc. These “foreign objects” should not come from the scrotum can cause bilateral scrotum unequal size, so how should we correctly understand bilateral scrotum unequal size and what are the common diseases? What are the common diseases? Pediatric inguinal hernia: all are hiatal hernias, almost always with congenital syringomyelia. Increased intra-abdominal pressure is then a precipitating factor for hernias, such as violent crying, prolonged bouts of coughing, constipation and difficulty in urination in children. Hernias occur easily in infancy and their incidence decreases after the age of 2 years. The abdominal organs that enter the hernia sac are most often the small intestine in infants and most commonly the uterus and adnexa in girls. Therefore, inguinal hernia in girls is prone to ischemic necrosis of the ovaries when it occurs and should be taken seriously by parents. The common manifestation of inguinal hernia is the protrusion of a mass in the groin and scrotum when the child is crying. The mass may disappear after lying down, but when the inguinal hernia becomes incarcerated, a painful mass appears in the groin or scrotum. The child cries and is restless, and later gradually develops nausea and vomiting. If left untreated, the symptoms of intestinal obstruction gradually worsen, abdominal distension becomes obvious, and vomiting is the intestinal contents. If bloody stools and red scrotal skin congestion occur, one should be alert for intestinal necrosis and testicular necrosis. Although the peritoneal sphincter may remain occluded after birth, children with hernias are rarely likely to heal spontaneously. Therefore, inguinal hernias, once diagnosed, should be treated surgically to prevent multiple occurrences of inguinal hernia entrapment. Pediatric syringomyelia: Syringomyelia is formed when the sphincter remains open or partially open due to incomplete occlusion of the sphincter, and because of the small diameter of the sphincter, the intestinal canal cannot pass through, allowing only abdominal fluid to flow through the sphincter and accumulate in the sphincter cavity. The sphincter in female fetuses is called Nück’s duct, and if fluid accumulation occurs it is called Nück’s cyst. Syringomyelia generally has no systemic symptoms and only localized lumps in the groin and scrotum, which vary in size, grow slowly and do not cause pain. Larger masses may have a feeling of scrotal swelling. The masses of syringomyelia often appear to be filled and swollen with high tension after walking activities during the day; they may be slightly shriveled in the morning when they wake up. Syringomyelia in newborns may occur unilaterally or bilaterally. If the syringomyelia occludes itself during development, the syringomyelia gradually disappears. If the syringomyelia is not large and the tone is not high, there is no urgency to treat it surgically, especially in infants under 1 year of age, as it has a chance to resolve on its own. If the tension is high, it may affect the blood supply to the testes and produce testicular atrophy. Cryptorchidism: Also known as undescended testis or incomplete testicular descent, refers to the failure of the testis to descend from the lumbar retroperitoneum to the scrotum according to the normal development process. The main manifestation is the poor development of the scrotum on the affected side, the scrotum is empty and the testicles cannot be found. Sometimes the testicle can be found in the inguinal region or in the perineum outside the scrotum, which is usually smaller than normal and locally visible as a bulge. Cryptorchidism is often accompanied by unclosed sphincter on the affected side, which can be manifested as syringomyelia or inguinal hernia. After the diagnosis of cryptorchidism is clear, treatment should be done as soon as possible to lower the testicle in abnormal position to normal scrotal position, and it should be done before 2 years old. The treatment of cryptorchidism is mainly surgical treatment, i.e. testicular fixation, and the combined inguinal hernia can be treated at the same time as the surgical treatment. At present, hormonal treatment is not recommended by domestic and foreign scholars. Pediatric testicular tumor: It is less common, accounting for only 1% of pediatric tumors, and the age of prevalence is about 2 years old. Teratoma is the most common benign testicular tumor, and the most common malignant testicular tumor is yolk cystic tumor. Most pediatric testicular tumors present as painless scrotal masses, and physical examination reveals enlarged testicles on the affected side without tenderness and opacity, which may be accompanied by syringomyelia. Ultrasonography is preferred for clinical diagnosis, and CT examination is feasible if lymph node metastasis is suspected. Commonly used tumor markers are alpha-fetoprotein (AFP) and human chorionic gonadotropin (HCG). For malignant testicular tumor, AFP and HCG can be significantly increased. Once diagnosed, testicular tumors should be treated with surgery as soon as possible. Pediatric testicular epididymitis: It is an infectious disease of the reproductive system in children, manifesting as sudden pain and swelling in the scrotum, swelling of the epididymis, and obvious tenderness, which may be accompanied by fever, hard nodules in the epididymis, and other discomforts. Ultrasound examination is preferred for clinical diagnosis, and anti-infection treatment is the main treatment for pediatric testicular epididymitis. Pediatric testicular torsion: It is an ischemic lesion of the testis caused by torsion of the spermatic cord. It is one of the diseases of acute scrotal swelling and pain in children, manifesting as sudden onset of persistent pain in one testicle, which may increase paroxysmally with nausea and vomiting. The scrotal skin is congested, edematous and feverish. On physical examination, the scrotum is enlarged and painful. The testicle is enlarged and moves up to the scrotal root in a transverse position, which is a specific sign of the disease. The testicular reflex on the affected side is absent. The scrotal redness and swelling gradually increase and become hard. Ultrasonography is preferred for clinical diagnosis. It can sensitively detect changes in testicular blood flow and is a quick, easy, non-invasive, painless and repeatable test, with a diagnostic accuracy of 81% to 90%. The goal of testicular torsion treatment is to save the testis and protect fertility and endocrine function. Therefore, in patients with scrotal emergencies, those with testicular swelling, swelling, pain, lifting pain, and suspected testicular torsion, surgical exploration should be performed as early as possible to improve the testicular salvage rate. Treatment within 6h after the onset of symptoms is crucial.