The small intestinal mesenteric lymph nodes are arranged along the mesenteric artery and collect intestinal lymphatic fluid and then inject into the lymph nodes at the root of the superior mesenteric artery and the anterior abdominal aortic lymph nodes, and finally into the celiac pond. The intestinal lymphatic drainage is abundant, with the ileocecal region being the most prominent, so there are more lymph nodes near the ileocecal region. Viruses, bacteria and their metabolites in the intestine are easily absorbed into the ileocecal lymph nodes, and inflammatory lesions in the intestine also easily involve the mesenteric lymph nodes, causing mesenteric lymphadenitis. Acute mesenteric lymphadenitis occurs in children under 7 years of age. It is mostly a viral infection. It occurs in winter and spring and often develops during respiratory tract infections. Symptoms: Typical symptoms are fever, abdominal pain, vomiting, sometimes accompanied by diarrhea or constipation. The abdominal pain can be anywhere, but mostly occurs in the right lower abdomen and around the umbilicus. The abdominal pain often presents as indistinct vague or colicky pain, which improves between episodes of abdominal pain. Abdominal examination: the abdomen is soft and there is no fixed pressure pain. There are no systemic symptoms and the child is in good spirits. Blood test: normal or mildly elevated white blood cells. Treatment: Generally, after fasting, infusion and antibiotic treatment, abdominal pain improves significantly without surgical treatment. Mesenteric lymph nodes accompany people throughout their lives and are normal structures. They only become larger after inflammation, but the lymph nodes retract very slowly after the inflammation subsides. That’s why the lymph nodes are still very large when you have an ultrasound 2-3 weeks after having mesenteric lymphadenitis, but it’s okay. In addition, the ultrasound done in a child with abdominal pain reveals large lymph nodes, not necessarily the cause of this pediatric abdominal pain. Or the discovery of large pediatric abdominal lymph nodes does not necessarily mean that the child is suffering from mesenteric lymphadenitis at this time. There are many causes of pediatric abdominal pain, and it is not necessary to take medication, especially antibiotics, when a large pediatric mesenteric lymph node is found. Second, septic mesenteric lymphadenitis This disease is rare and the cause is unclear. Bacteria can come from the intestine, respiratory tract, skin, latent in the intestinal lymph nodes. Once the body’s resistance decreases, the bacteria multiply and cause septic infection of the mesenteric lymph nodes. Symptoms: Rapid onset, sudden onset of abdominal pain, fever, abdominal distension, diarrhea, pain around the umbilicus or right lower abdomen. The abdominal pain is persistent with paroxysmal exacerbation. It may cause intestinal paralysis with abdominal distention, vomiting, and cessation of defecation and exhaustion. The mesenteric lymph nodes become septic and form abscesses or rupture, causing peritonitis. Systemic symptoms are severe and the child is depressed. Blood test: increased white blood cells. Treatment: Most require hospitalization for surgery.