Enlarged abdominal lymph nodes in children are likely to be caused by mesenteric lymphadenitis, immune system diseases and lymph node metastasis of malignant tumors, or can be caused by physiological factors. 1. Mesenteric lymphadenitis: mesenteric lymphadenitis often develops from upper respiratory tract infection. Viruses, bacteria and other pathogens infecting the upper respiratory tract circulate to the mesentery with the bloodstream, and there are more lymph nodes in the mesentery, especially the end of the ileum and the ileocaecum. When the mesenteric lymph nodes are inflamed, under the double stimulation of inflammatory factors and pathogens, the lymph nodes will be enlarged. 2. Immune system diseases: patients with immune system diseases such as systemic lupus erythematosus, Kawasaki disease and rheumatoid arthritis, etc., their autoimmune system is over-excited, and when the immune system attacks the lymphatic system of the whole body, it can lead to lymphocyte hyperplasia, which can lead to the enlargement of lymph nodes of the abdominal cavity. 3. Malignant tumor lymph node metastasis: if there is a malignant tumor metastasis to the abdominal lymph nodes, because of the continuous proliferation of malignant tumors, it may lead to its enlargement. 4. Physiological factors: children in the process of growth and development, the abdominal cavity and other parts of the lymph nodes will grow, if there are no other uncomfortable symptoms, such as fever, nausea, vomiting, loss of appetite, etc., you can observe, follow up can be. If the child’s abdominal lymph nodes are enlarged, parents should pay attention and take the child to the hospital in time to find out the cause of the disease, and then individualized treatment will be implemented by professional doctors.