Jack is 8 years old, and returned today from a holiday in Turkey. His parents report he has been complaining of abdominal pain for the past 3 days, and that he has been having constant diarrhoea – at least hourly – over the past 36 hours. He passed a small amount of urine yesterday night Mum reports she has seen blood in his last bout of diarrhoea. On initial examination you note he has sunken eyes and dry mucous membranes. His capillary refill time is normal and he is not tachycardic.