Hemorrhagic gastroenteritis is an acute condition of dogs characterized by the sudden onset of severe bloody vomiting and explosive bloody diarrhea. Large amounts of fresh blood are passed in the vomit and diarrhea, leaving the animal weak, depressed, and reluctant to eat. As the disease progresses, pets rapidly deteriorate, becoming shocked and collapsed. This is a life-threatening situation that requires immediate treatment. The mortality rate is high for dogs that go untreated.
The actual cause of hemorrhagic gastroenteritis is unknown. There are several theories that HGE may be caused by a viral infection, bacterial infection, bacterial toxins, or immune-mediated destruction of the intestinal lining. The disease usually occurs in healthy animals with no history of concurrent illness.
Full information can be found at this link Hemorrhagic gastroenteritis (HGE).