A 7 year old girl presents to your ED with a 5 day history of diarrhoea and feeling generally unwell. The patients mum reports episodes of blood and mucous in the stool. She is tachycardic and appears unwell.

Describe and Interpret her blood results

Hb                77               (115-155 g/l)

MCHC          345              (320 -360 g/l)

MCV              84               (82-99 fl)

MCH              29               pg

Platelets         60              (140-400 X 10^9/l)

WCC             14               (4-11 X10^9/l)

Na                 139             (134-146 mmol/l)

K                   4.2              (3.4 – 5.5 mmol/l)

Cl                  107             ( 95-108 mmol/l)

HCO3            25               (22 -32 mmol/l)

Urea              12               (3 – 8 mmol/l)

Creatinine      130             (30 – 100 mmol/l)

What is the likely diagnosis and how would you investigate this patient?