Retroperitoneal lymph nodes with clear borders are lymph nodes with clear borders that appear in the retroperitoneum when the patient undergoes abdominal CT or ultrasound, which are mostly considered to be caused by benign lesions, such as Crohn’s disease, tuberculous peritonitis, and mesenteric lymphadenitis, and so on. 1. Crohn’s disease: patients with Crohn’s disease will have fever, abdominal pain, diarrhea and other manifestations. In addition, patients can not only know the degree of narrowing of the intestinal lumen, but also check the appearance of retroperitoneal lymph nodes with clear boundaries with the surrounding. 2. Tuberculous peritonitis: patients with abdominal pain, abdominal distension, night sweats, low-grade fever and other manifestations. In addition, Mycobacterium tuberculosis will enter the lymph nodes through the abdominal tissue fluid, which will lead to the enlargement of abdominal lymph nodes, so the patients will have the manifestation of localized retroperitoneal lymph nodes with clear boundaries in the abdominal CT examination. 3. Mesenteric lymphadenitis: mesenteric lymphadenitis may be caused by bacterial, viral, parasitic and other pathogens. It is recommended to do abdominal CT or ultrasound examination, the appearance of clear boundaries of the retroperitoneal lymph nodes, you need to consult a doctor in a timely manner, the doctor will choose the appropriate measures for the treatment of the patient’s condition.