The presence of multiple lymph nodes in the abdominal cavity is clinically common in two main groups of diseases: first, mainly inflammatory diseases, the most common being mesenteric lymphadenitis in children. It is usually preceded by a history of upper respiratory tract infection in the week prior to onset, followed by abdominal pain, and is easily confused clinically with acute appendicitis, which is wandering and has no fixed pressure points. Ultrasound examination usually shows multiple enlarged lymph nodes in the mesentery, and treatment is mainly antiviral as well as antibiotic therapy. The second type, mainly seen in gastrointestinal malignancies, is the presence of retroperitoneal lymph node metastasis, which usually means that the disease is in the middle or advanced stage, and further enhanced CT examination of the abdomen is needed to understand whether there are metastases in the liver and other organs. When conditions permit, radical resection of gastrointestinal malignancy and lymph node dissection are usually required. Adjuvant chemotherapy and, if necessary, radiotherapy are also required after surgery.