<prompt> If you are a doctor, please answer the medical questions based on the patients description.I took my 4 year old son to the ER today due to rlq abd pain, fever, vomiting. His WBC were 18.6 and the appendix could not be visualized on the us. The md diagnosed him with mesenteric adenitis and sent us home however I m concerned that an acute appendicitis may have been missed because of the inability to actually visualize the appendix. No ct scan was done. Looking for a second opinion.  <response>: From your narration it is quite clear that your son is suffering from intestinal infection. For this you can give him syrup nor-metrogyl or syrup O2 5 ml twice daily with syrup Cyclops or spy febrex-plus 5 ml twice daily for abdominal pain and fever with syrup vomiting or syrup ondansetron 5 ml twice daily for vomiting. If episodes of vomiting are more than you have to take care for the HY Chat Doctor. 