A 15 year old boy presents to the clinic with vomiting a lot for 5 hours.  He has vomited 4 times, it is yellow in colour and not projectile. He does not have any reported abdominal pain. He has voided 3 times today and has had one normal bowel movement. Earlier this morning he was playing soccer and was struck by another player. There was brief loss of consciousness. He sustained no obvious injuries.

Physical Examination: He looks well.  Abdomen is not distended. On auscultation, bowel sounds are normal. On palpation it is non-tender and there are no masses or organomegaly. The remainder of the physical examination is normal.