Enlarged lymph nodes in the abdominal cavity are commonly caused by intra-abdominal infections, including peritonitis or inflammation of the abdominal organs, spontaneous infections, and abdominal pain, abdominal distention, nausea and vomiting, which can also lead to enlarged lymph nodes in the abdominal cavity, retroperitoneum, and the root of the mesenteric vessels. The most effective treatment is anti-infective therapy, usually combined with intravenous cephalosporin and metronidazole, and, if complicated by a significant abscess or severe abdominal infection, surgery to drain or remove the primary infected lesion, if necessary. Postoperative treatment also requires continued symptomatic support to prevent ionic disturbances and acid-base imbalances. Mild cases usually improve with aggressive anti-inflammatory therapy, while severe cases require adjuvant intravenous chemotherapy if necessary, which is the complementary treatment for patients with malignant tumors after surgery.