What type of infection is it when your dog bleeds from the rectum and is throwing up?

i just had my dog hospitalized tonight because she was throwing up and then started to bleed from her rectum ( alot of clumpy blood started to come out) i know that there is a deadly infections the doctor tested her for that and thank god it was negative i had to leave her overnight so that they can run more test on her what other type of infections might she have. she is very weak and has not really eaten in the last few days