Enlargement of mesenteric lymph nodes refers to the enlargement of lymph node tissues around the mesentery detected by imaging or ultrasound, and common causes include physiological enlargement in children, infection, lymph node metastasis of malignant diseases, and blood system diseases. There is no uniform diagnostic standard for enlarged mesenteric lymph nodes. According to references, most scholars in China believe that if more than 3 lymph nodes are shown in the mesenteric region in one section, with the largest lymph node having a long diameter of more than 1.0 cm and a short diameter of more than 0.5 cm, and with a long diameter/short diameter of more than or equal to 2, it can be diagnosed as an enlarged mesenteric lymph node. As the lymphatic system is proliferating actively in children, mesenteric lymph nodes can be seen in the abdominal ultrasound examination of healthy children, which belongs to the normal physiological mesenteric lymph node enlargement. In addition, abdominal, gastrointestinal and systemic infections can lead to reactive enlargement of lymph nodes, and lymph node metastasis of malignant tumors and hematological diseases such as lymphoma can lead to malignant proliferation of lymphatic tissues and enlargement. Therefore, it is recommended that the cause of mesenteric lymph node enlargement be clarified according to the specific symptoms and other examinations, and timely treatment be carried out.