Rectal bleeding in cats can be caused by constipation. When a cat is constipated, it will often pass hard or overly bulky stools. These can damage and irritate the skin of the rectum and anus, resulting in bleeding. If your cat ingests poison, it could bleed from its bottom. Poisons designed to eliminate rats and mice are called anticoagulant poisons because after an animal ingests them, they block the normal clotting properties of the animal's blood, according to "Cat Owner's Home Veterinary Handbook." Cancer of the gastrointestinal tract, called intestinal adenocarcinoma, will also cause intermittent rectal bleeding.
A constipated cat can develop proctitis, or inflammation of the rectum and anus. When this happens, the skin becomes visibly ulcerated and irritated. Your cat may lick at it, attempting to soothe the pain, which may be an early indicator of the problem. A cat that has ingested an anticoagulant poison will bruise easily, have nosebleeds and could also vomit blood. If your cat is bleeding from its bottom because of cancer, it will also vomit, lose weight and avoid eating.
If your cat is experiencing rectal bleeding, then its stools will be coated in blood, rather than having the blood mixed in with the fecal matter. A constipated cat will pass hard stools and will often stop squatting during bowel movements. Your veterinarian can diagnose poisoning by examining your cat's gums and by looking at the poison it had access to. According to "Small Animal Clinical Oncology," your veterinarian can tell if your cat has intestinal adenocarcinoma by checking to see if it is hypoglycemic (has low blood sugar) and by using abdominal radiography to look for intestinal tumors.
You can treat constipation by feeding your cat a high-fiber diet. Laxatives can help prevent hard stools. Soothing ointments are available to relieve the pain of proctitis while your cat heals. If your cat ingests poison, contact your veterinarian right away. She can give your cat a blood transfusion and administer vitamin K to counteract the poison's effects. Intestinal adenocarcinoma is treated with surgery to remove the cancerous mass first, followed by radiation therapy to target any material left behind.
If your cat is straining in the litter box or if you hear it cry during a bowel movement, it is a good idea to bring your cat to the veterinarian to find out if it is experiencing an intestinal problem. Any poisons in your home should be properly sealed and stored in a way that prevents the possibility of accidental ingestion. Also, be aware that if poison kills a rat and your cat eats the dead rat, your cat could ingest the poison
Hope your kitten get's better:)