Enlargement of abdominal lymph nodes in children is most likely to be mesenteric lymphadenitis, which may also be caused by ulcerative colitis, mesenteric lymphatic tuberculosis, intestinal tuberculosis, etc., or by metastasis of malignant tumors and other causes. 1. Mesenteric lymphadenitis: it is a common disease in childhood. It is usually characterized by abdominal pain, fever and vomiting. Most of the mesenteric lymphadenitis in children is caused by viral infection, so active antiviral treatment is needed. 2. It may be caused by ulcerative colitis, mesenteric lymphatic tuberculosis, intestinal tuberculosis and so on, all these diseases may lead to the present abdominal lymph node enlargement. 3. Malignant tumors: malignant tumors in the stomach, colon, rectum and other parts of the child may cause lymph node metastasis, which may also lead to abdominal lymph node swelling. If the child has swollen lymph nodes in the abdominal cavity, parents should bring the child to the hospital in time for relevant examination to make a clear diagnosis and carry out targeted treatment under the guidance of doctors.