During chemotherapy, the lymph nodes around the retroperitoneal abdominal aorta and the root of mesenteric lymph nodes are enlarged, if there is metastasis, we should continue anti-tumor treatment, and if it is judged to be inflammation, we can treat it as anti-infection treatment, and it is recommended that we should consult a doctor in time, so that the professional doctor can adjust the chemotherapy program or anti-infection treatment according to the actual situation of the patient. 1. Chemotherapy for metastatic lesions: during chemotherapy, the lymph nodes around the retroperitoneal abdominal aorta and mesenteric root are found to be enlarged, and it can be judged whether there is the problem of metastasis of malignant tumors according to the results of abdominal enhanced CT, such as the existence of colon malignant tumors, liver malignant tumors, which can invade the abdominal aorta, thus causing the enlargement of the lymph nodes. If the swelling of lymph nodes is related to tumor invasion, it is recommended to continue chemotherapy or change the chemotherapy regimen under the guidance of doctor. 2. Inflammation and anti-infection treatment: in this case, it is also considered that there may be acute inflammatory reaction, such as patients with purulent appendicitis, gastrointestinal perforation can cause reactive hyperplasia of lymph nodes in abdominal aorta, and it can be tried to use antibiotics for anti-infection treatment, which can be chosen as intravenous injection of cefoperazone sodium and oral cefadroxil. If the abdominal aorta and mesenteric lymph nodes are found to be enlarged during treatment, it is recommended to consult the oncology department of regular hospitals and follow the doctor’s instructions for treatment.