The presence of blood in vomit or in the stool (poo) is a common reason for children to be referred to the Paediatric Gastroenterology and Hepatology service.  The blood may be red or sometimes may cause tarry black stools. The cause will depend on the age of the child and may include oesophageal varices, (abnormal blood vessels at the bottom of the food pipe), stomach or duodenal ulcers, gastro-oesophageal reflux, Helicobacter pylori infection, inflammatory bowel disease, allergic colitis (allergic inflammation affecting the large intestine) or colonic polyps (non-cancerous growths) affecting the lining of the large intestine. The best way to find out the cause is a gastroscopy or colonoscopy (see above).  The urgency of this procedure will depend on the amount of blood passed and how unwell your child is due to the bleeding.