Slightly enlarged retroperitoneal lymph nodes may be caused by inflammation, diseases of the lymphatic tissues themselves, or neoplastic diseases. 1. Inflammation: Peritonitis, enteritis, pancreatitis or inflammation of the lymph nodes themselves caused by viral or bacterial infections may cause increased enlargement of the retroperitoneal lymph nodes. Respiratory infections in children may also cause enlargement of peritoneal or mesenteric lymph nodes. 2. Lymphatic tissue diseases: leukemia, lymphoma and other lymphatic tissue diseases, lymphocyte proliferation and differentiation, loss of normal physiological function. Pathological biopsy should be carried out in time to clarify the nature of the lesion, and symptomatic treatment or radiotherapy should be carried out. 3. Tumor diseases: when lymphatic metastasis occurs in gastrointestinal cancer, kidney cancer, liver cancer, pancreatic cancer and other tumors, they will invade infiltrated lymphocytes and proliferate and differentiate in them, so that lymph nodes will increase in size. It should be noted that when the above phenomenon occurs, one should go to the hospital in time for examination and treatment under the doctor’s guidance.