Enlarged abdominal lymph nodes may be caused by inflammatory infections or by tumor metastases, and the treatment of the two is different. Lymph node enlargement caused by inflammatory infection is usually seen in mesenteric lymphadenitis, which is more common in adolescents and usually has a history of upper respiratory tract infection one or two weeks prior to the onset of the disease. The main clinical manifestation is mild pain around and below the navel, which is intermittent and may be accompanied by an increase in body temperature, and there are usually no obvious signs of peritonitis. Ultrasound of the abdomen may reveal enlarged lymph nodes in the mesentery. Treatment is mainly oral antibiotics, such as cefixime and cefradine. If the enlarged lymph nodes are caused by tumor metastasis, there are usually primary lesions of tumor, such as gastric cancer and colon cancer. Gastroscopy and enhanced CT examination of abdomen should be performed to find the primary lesion. After the diagnosis is clear, radical surgery of tumor is usually needed. If the stage of tumor is too late to perform radical surgery, chemotherapy should be performed.