Pooping blood is not always a sign of something serious; however, there is a chance that the diagnosis could be one that requires immediate treatment. Always make an appointment with your veterinarian if your cat is passing blood in the stool.
Constipation
Constipation occurs when cats have trouble passing feces. The poop may be harder or another type of consistency and this may make it difficult to pass. Bowel movements can be infrequent or difficult to eliminate. Parasites, impaction, a foreign body, and certain illnesses like inflammatory bowel disease can cause constipation.
Anal sacs and itchiness
Anal sacs in cats are the anal glands in the rectal area. They can become impacted or abscessed and can cause bleeding in the stools.
Trauma
If a cat has been injured in the anal or rectal area, he may bleed when he goes to the litter box. Typically he will show signs of being injured. Polyps and injury due to a fistula or tear may cause your pet pain upon defecation.
Infection
If your cat has an infection in his colon or other part of his lower intestinal area of bowel, he may express pain when passing stool. An infection may cause internal bleeding that is present in the stools.
Cancer
If your cat has colon cancer or other type of intestinal cancer, he may have blood in his stools. Your cat may have other symptoms as well if he has cancer, such as weakness or loss of appetite.