First things first. Small children do bring up blood, only not as commonly as adults. Since it was dark red, it is likely that the blood is coming from lower down the gut like the small intestine
. Usually blood from the food pipe (esophagus
) is bright red, but dark red is from lower down. THe most common cause is still an inflammation of the small intestine but it could also be from what is called a 'meckel's diverticulum' . This is usually associated with pain in tummy as well.
Your child needs a meckel's scan and also would benefit from a upper gastroendoscopy.
Dr Antony Robert