The presence of lymph nodes in the abdominal cavity requires further refinement of relevant investigations and even surgical treatment if necessary. Under normal circumstances, abdominal lymph nodes cannot be properly visualized by current clinical imaging, including ultrasound or CT. If lymph nodes are found in the abdominal cavity by ultrasound or CT examination, the following two disease possibilities are usually considered: i. It is common in pediatric patients, mainly caused by mesenteric lymphadenitis secondary to upper respiratory tract infection, which manifests as wandering pain in the abdomen, usually with a history of upper sensation about a week before the onset of the disease. For mesenteric lymphadenitis, anti-inflammatory and antiviral treatment is usually chosen, and most of them can be cured without surgical treatment. Secondly, we should be highly alert to the possibility of gastrointestinal malignant tumor with lymph node metastasis, and we need to do further enhanced CT and gastroscopic enteroscopy to make a clear diagnosis.