Mesenteric lymphadenitis is a common and frequent disease in toddlers and school-age children, with varying degrees of pain, which can be tolerated by children in general, but can also be manifested as acute abdominal-like severe pain, which is difficult for children to tolerate. This disease is caused by the pathogen of upper respiratory tract infection entering the blood circulation of the child and then invading the mesenteric lymph nodes; it is also related to the exuberant development of the lymphatic system of children in this age group. Generally, the clinical symptoms of children with mesenteric lymphadenitis will be relieved soon after anti-infective and symptomatic supportive treatment, but recently, two children with mesenteric lymphadenitis were admitted to our department, which had a special condition and was rare in clinic, and they have been well treated so far. One of the children was admitted to the hospital because of paroxysmal abdominal pain for 5 days and vomiting for 3 days in a foreign hospital with mesenteric lymphadenitis (abdominal ultrasound confirmed the presence of enlarged lymph nodes) treatment for 4 days with poor results, and the child was found to be combined with allergic purpura (abdominal and cutaneous) and acute appendicitis after the physical examination. After active anti-infection, immunomodulation, anti-platelet, anti-allergy and other symptomatic supportive treatment, the child’s abdominal pain disappeared, the rash subsided, no further vomiting, and the urine routine was no abnormality, so the child was cured and discharged from the hospital, and continued to follow up. Another child was a 3-year-old toddler who was admitted to the hospital with paroxysmal abdominal pain for 4 days and fever for 2 days. Outpatient abdominal ultrasound showed reactive enlargement of mesenteric lymph nodes. After routine treatment, the child’s fever subsided, and the paroxysmal abdominal pain could not be effectively relieved, so he underwent further examination, and the ultrasound examination of the whole abdomen showed congenital dilatation of the common bile duct (there were no accompanying symptoms, such as jaundice of the skin). The child was discharged from the hospital after surgical treatment. Mesenteric lymphadenitis is a simple infectious disease with a good prognosis, and the author also saw a child with mesenteric lymphadenitis combined with adrenal neuroblastoma in a higher hospital, and the adrenal tumor was missed because of mesenteric lymphadenitis. All these cases remind us that even simple diseases need to be treated carefully, and we need to be vigilant about missing other conditions.