Multiple small lymph nodes in the abdominal cavity and retroperitoneum may be caused by infections, diseases of the lymph nodes themselves, and tumor diseases. 1. Infection: When infected by viruses, bacteria and other microorganisms, the lymph nodes proliferate and enlarge to resist infection, resulting in multiple small lymph nodes. It is common in chronic enteritis, peritonitis, pancreatitis, cholangitis and other abdominal infections. Antiviral drugs or antibiotics can be given according to the pathogen. 2. Lymph node diseases: lymphoma, leukemia and other lymph node diseases can lead to enlarged lymph nodes, which should be treated by pathological biopsy, symptomatic treatment or radiotherapy and targeted drug therapy. 3. Tumor diseases: metastatic foci of gastrointestinal cancer, lung cancer and other tumor diseases will invade infiltrated lymphocytes and proliferate and differentiate in them, resulting in enlarged lymph nodes. Symptomatic treatment or radiotherapy and targeted therapy should be given in time. It should be noted that when the above situations occur, one should go to the hospital in time for examination and treatment under the guidance of doctors.