According to the Fairmount Animal Hospital, rectal bleeding in dogs can be the result of any number of diseases or disorders of the colon, rectum or gastrointestinal tract, including anorectal disease, rectal prolapse, intestinal parasites or colonic ulcers. The color and consistency of the blood helps to pinpoint the problem.
According to Fairmount Animal Hospital, anorectal diseases can result in rectal bleeding and other symptoms, such as frequent defecation and mucus or blood in the feces. In the case of anorectal disease or problems with the lower gastrointestinal tract, which includes the colon and rectum, the blood is unclotted and bright red. Bleeding as a result of problems in the upper gastrointestinal tract produces blood that is dark and thick. Rectal polyps, rectal prolapse, cancer and colonic ulcers and inflammation are also problems in the lower gastrointestinal tract that result in rectal bleeding.
According to Pet Health & Care, rectal bleeding occurs most commonly due to inflammation. Inflammation in both the colon and the rectum results in diarrhea and constipation. Upon noticing rectal bleeding in dogs, pet owners need to take the animal to the vet immediately, especially if it is accompanied by other symptoms, such as bleeding from other parts of the body and listlessness.