As a mother I am going to suggest you follow your gut instinct. If you feel this neuro is doing more harm than good then don't allow him to do this testing and don't put your son through testing that you feel will be more harmful.

I would think a test such as an abdominal CT scan involving a nasogastric tube is something left for his Gastroenterologist not the Neurologist.

Please seek another opinion. Do you have a Children's Hospital fairly close? If so that might be a better choice for your son ---