Our animal companions can have blood in the stool for a variety of medical reasons. Blood in the stool is most commonly due to colitis, which is an inflammation of the lining of the colon. One of the first tests that should be performed on a pet with blood in its stool is a fecal check for intestinal parasites to look for roundworms, hookworms or whipworms. Giardia is also a common intestinal parasite that may cause vomiting, as well as blood in the stool. If the stool check is negative, other causes of blood in the stool should be explored including dietary indiscretion, ingested foreign bodies, dietary allergy, inflammation of the liver and inflammation of the pancreas. Viral and bacterial infections may also cause bloody stools in dogs and cats.
Probably the most common cause of chronic blood in the stool in middle-age to older pets is an autoimmune disease known as inflammatory bowel disease. Especially in middle-age and older pets it is important to rule out any underlying cancer including in the lower digestive tract or rectal area.
Pets with blood in the urine most commonly have urinary tract infections. However, in many cases urinary tract crystals and/or stones may be present. In middle-age and older pets, chronic blood in the urine also could be due to urinary tract polyps or tumors of the bladder, urethra or prostate. It is for these reasons that any pet with chronic blood in the stool or urine should have a full veterinary medical workup to insure a proper diagnosis and treatment plan.