Broad differential: Gastrointestinal, Neurologic, Metabolic, Respiratory, Renal, Infectious, Endocrine, Toxin-related, Behavioral
Nausea and vomiting 
Esophageal stenosis/atresia
Fever and rash
Pyloric stenosis
Abdominal pain 
Intestinal stenosis/atresia
Abdominal pain
Duodenal atresia