Multiple enlarged lymph nodes 1.1×0.5cm in the abdominal cavity of a nine-year-old child may be related to respiratory tract infection, gastrointestinal tract inflammation, lymphoma and other factors. 1. Respiratory tract infection: when children develop respiratory tract infection, it may lead to inflammation of lymph nodes in the body, including mesenteric lymph nodes. 2. Inflammation of gastrointestinal tract: any infection of the gastrointestinal tract by bacteria or viruses may lead to enlarged mesenteric lymph nodes. 3. Lymphoma: Lymphoma may also cause the above conditions in children, and there may be abdominal pain in the later stage. Nine-year-old child abdominal cavity multiple enlarged lymph nodes 1.1×0.5cm, there may also be other reasons, it is recommended to go to the hospital in a timely manner, improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.