Take your cat to your veterinarian. This is why:
Serious, and even potentially fatal diseases can cause blood in the stool. Inflammatory bowel disease and intestinal parasites are fairly common causes of intestinal bleeding. It can also be associated with blood clotting problems due to mouse poison, other toxicities and immune mediated diseases. Colon cancer can cause blood in the stool or around the anal area. Foreign objects such as strings or bones eaten by the cat can also cause rectal bleeding. Anal gland infections can cause blood on the stool and painful defecation, and constipation can cause rectal tears and bleeding to occur as well.
When fresh blood is seen in the stool we know that there is damage to the lining of the colon or anus. If bleeding occurs in the small intestine, typically we will see black tarry stools as the blood is digested as it passes through the small intestine. With inflammation in the colon, we often see bright red blood that may be present along with mucus and frequently is coating the outside of the stool. Occasionally small drops of blood can be seen in the litter as well. Intestinal inflammation serious enough to cause either obvious bloody stools or tarry stools can allow bacteria to migrate through the intestinal wall causing sepsis or other serious infections in the kidneys, liver and other organs.
Bring a fresh (within 24 hours of passing) stool sample with your cat to your veterinarian so it can be tested for intestinal parasites. Some intestinal infections can be transmitted to humans from cat stool so wash your hands after packaging the stool sample in a plastic bag. Don’t freeze the stool sample but you may refrigerate it for up to 24 hours before your appointment. It is OK to have litter on the sample. Just make sure that is a stool sample and not a urine clump!
Parasites such as coccidia and Giardia can cause blood in the stool, often associated with diarrhea as well. Some cats have blood in the stool due to viral infections such
as feline panleukopenia, which can be serious and even fatal. Tumors can occur in the colon although these are uncommon. Your veterinarian will most likely do a rectal exam looking for abnormalities in the colon. Lab testing such as a complete blood cell count (CBC), blood chemistry, electrolytes, thyroid testing, clotting profile and urinalysis may be needed. Sometimes fecal samples need to be submitted to a reference lab to look for small amounts of certain intestinal infectious agents with DNA pathogen testing. Occasionally intestinal and pancreatic function blood tests may be needed. In addition, fresh fecal material may need to be directly obtained from the colon for microscopic examination. Finally, some cats may need an X ray or abdominal ultrasound looking at the colon and small intestine along with other abdominal organs.
If infectious causes and obvious tumors are ruled out, then treating for inflammatory bowel disease is often indicated. The only definitive diagnosis for inflammatory bowel disease and some intestinal tumors such as lymphoma is via intestinal biopsies. These can be done surgically or with endoscopy. Many times if biopsies are not possible we may perform a therapeutic trial of anti-inflammatory steroids and an antibiotic called metronidazole. If we see significant improvement, it does not necessarily rule out intestinal tumors such as lymphoma, although it does
make inflammatory bowel disease more likely.
Finally, occasionally people mix up blood in the litter box from stool versus blood in the urine. Male cats that are passing bloody urine may have a partially obstructed urethra, which can progress to full obstruction and death if not addressed. This is less likely but not impossible in female cats. Blood and urine can also be due to inflammation such as cystitis, urinary tract infections and even kidney stones.
Never ignore blood in the litter box or on your cat’s stool- you may be saving your cat’s life by seeking medical attention early.