Colitis: is an inflammation of the colon or lower bowel, and has many different causes, from bacterial infections to allergies. Since causes vary so do symptoms and treatments. Generally, you might see feces with mucus or blood in it, bloody diarrhea, or unproductive straining after passing feces. Severe dehydration can kill a Cavalier King Charles Spaniel (dog) quickly so immediate veterinary care is crucial.
