You can determine whether your 4-year-old child has a megacolon by clinical symptoms and ancillary tests. Usually, the common clinical symptoms of megacolon include delayed defecation, abdominal distension, constipation and so on. If a 4-year-old child has these symptoms, he or she should be taken to the hospital in time for diagnosis of megacolon through barium enema, rectal anal tube manometry, rectal tissue biopsy and other auxiliary examinations. 1. Clinical symptoms: megacolon can be divided into congenital megacolon, secondary megacolon and megacolon homologous disease. Among them, congenital megacolon is often manifested as delayed defecation, abdominal distension and constipation; secondary megacolon is often manifested as defecation, malnutrition, developmental delay, diarrhea, etc.; megacolon homologous disease is manifested as intermittent constipation. 2. Auxiliary examination: If 4-year-old children with common clinical manifestations of megacolon, in order to clarify the diagnosis also need to carry out auxiliary examinations, such as barium enema, to understand the morphology of the colon; rectal canal manometry, to see whether the child lacks rectal ganglion cells; rectal biopsy, to clarify the development of the rectal nerve status. Based on these ancillary tests, the presence of megacolon in the child can be determined. If the baby has abdominal distension, constipation, delayed defecation and other common symptoms of megacolon, it should go to the hospital in time for examination, a clear diagnosis, and carry out targeted treatment as soon as possible to prevent the aggravation of the situation of megacolon.