Blood in the stool of a 4-year-old child usually does not require a colonoscopy if it is caused by acute enteritis, anal fissure, etc. However, if it is caused by intestinal polyps or if the cause of the blood in the stool cannot be determined, a colonoscopy should be performed. There are many possible diseases that may cause blood in the stool of a 4-year-old child, and not all of them may require a colonoscopy. If it is caused by acute enteritis, routine stool or stool culture tests can be performed, usually without colonoscopy; if it is caused by perianal diseases such as anal fissure, perianal examination or routine stool examination is usually required, and colonoscopy is usually not necessary. However, if intestinal polyps are suspected, enteroscopy should be considered to clarify the cause of the disease or to perform microscopic polypectomy. In addition, if the cause of blood in stool cannot be clarified, colonoscopy should also be performed to clarify whether the blood in stool is caused by intestinal mucosal lesions. When blood in stool occurs in 4-year-old children, it is recommended to seek prompt medical attention to identify the cause of the disease to avoid delay. The need for colonoscopy should be decided after a comprehensive assessment by a doctor.