A few red droplets on the carpet or an unusually foul smell from the litter box may indicate that your cat is bleeding from his back end. Of course, visible blood on his rear is an obvious sign of trouble. Don't rely on visual inspections alone though, because some causes of bleeding aren't always apparent.
About Rectal Bleeding in Cats
Polyps and Tumors
Unnatural growths near the end of your cat's digestive tract obstruct the passage of waste and may cause sporadic bleeding. Polyps generally are benign, but these tiny nodules can be painful and may lead to prolapse if left untreated. Polyps can protrude visibly from the anus or remain unseen inside your cat's body. Affected areas are sensitive and bleed easily when disturbed. Veterinarians can check your cat for benign and cancerous growths with a physical examination of the intestinal lining. Cancerous tumors often require chemotherapy or other aggressive treatment, while polyps are removed with simple surgery, according to The Merck Manual for Pet Health.
Digestive diseases and constipation may force your cat to put extra strain on his muscles when using the litter box. This pressure can force a portion of his intestinal lining outward so that it's visible externally. Rectal prolapses are painful for kitties and should be addressed by a professional vet as soon as possible. Pet owners should not touch or try to fix a prolapse on their own. Simple surgery is usually sufficient to fix minor prolapses, but severe cases require invasive and expensive treatment.
Worms and other parasites also may be to blame for your cat's bleeding. Hookworms and tapeworms latch on to the lining of the intestines to steal nutrients from their host's blood. Uncontrolled infestations can cause a life-threatening drop in blood supply in smaller animals. Felines with worms lose blood when they defecate, which makes stool tarry and darker in color, according to Cornell University College of Veterinary Medicine. Protozoan parasites also can cause rectal bleeding in cats. Management strategies for parasites depends on the type and scope of infestation, so a professional diagnosis is necessary before you begin treatment.
Allowing your cat to swallow a needle or a narrow chicken bone can be an excruciating and costly mistake. Foreign objects can tear through sensitive tissue as they pass with your cat's feces. Bleeding often accompanies complete or partial tears. Your cat also may struggle to relive himself or avoid the litter box entirely. Bite and scratch wounds around the anus can draw significant amounts of blood, since the area has many veins and arteries that carry nutrients away from the intestines. Wounds around the rectum usually require minor surgery, since the pressure of defecating can prevent them from closing naturally.