In clinical practice mesenteric lymph nodes are normally invisible on imaging, which means that there is no so-called normal value. Enlarged mesenteric lymph nodes are mainly seen in two clinical situations: a. Children with enlarged mesenteric lymph nodes, which appear as enlarged lymph nodes on imaging, are usually suffering from mesenteric lymphadenitis, with a history of upper respiratory tract infection about a week before onset, followed by abdominal pain or even diarrhea, which can usually be relieved or even cured after anti-inflammatory treatment for about a week. In adults, enlargement of mesenteric lymph nodes or even enhanced CT shows intensified shadow, which usually represents lymph node metastasis of gastrointestinal malignant tumor, and further gastroscopy or colonoscopy is needed for clear diagnosis. When the diagnosis of malignant tumor with mesenteric lymph node metastasis is made, it usually requires radical resection by surgery, or even combined with postoperative chemotherapy or even radiotherapy to obtain a cure.