Slightly enlarged mesenteric lymph nodes in adults may be caused by microbial infection, tuberculosis or tumor disease. 1. Microbial infection: When bacteria, viruses and other microbial infections, lymph nodes as immune organs will proliferate and become bigger in order to resist the infection, which can be manifested as an increase in the number of lymph nodes and enlargement. Bacterial culture and drug sensitivity test should be carried out in time, and appropriate antibiotics and antiviral drugs should be used for treatment. 2. Tuberculosis: Tuberculosis caused by Mycobacterium tuberculosis will lead to lymph node enlargement and increase in size. Anti-tuberculosis drugs such as isoniazid and rifampicin should be used to treat the disease, and the principles of early, combined, appropriate amount, whole course and regularity should be observed. 3. Tumor diseases: when cancer and other tumor diseases recur and metastasize, cancer cells can infiltrate lymphocytes and proliferate and differentiate in them, so that lymphocytes will increase in number and become bigger. Pathological examination should be carried out in time to clarify the nature of lesions and carry out symptomatic treatment. It should be noted that when the lymph nodes increase in size, one should go to the hospital in time for examination and treatment under the guidance of doctors.