Hernia is a common disease in children, the incidence rate is 3-5%, more boys than girls, more right than left, some children are bilateral, so how does a hernia form? Here I will tell you. A hernia is caused by a hole in the lower abdomen of a child that does not close. The mechanism of this hole is different for boys and girls. The testicle is a retroperitoneal organ and when it descends, it comes down with a layer of peritoneum and folds at the location of the inner ring mouth to form a pouch structure called the sphincter, which is connected to the abdominal cavity through a small hole. Most of the children’s sphincters will close on their own as they develop, but some of the children’s intestines and omentum in the abdominal cavity come out due to crying, coughing, constipation and other triggers, and a hernia is formed, because the right testicle descends later than the left, so the incidence is higher on the right side. In girls, this is caused by the fall of the round ligament of the uterus, and the contents of the hernia in girls may also be the ovaries.