Like humans, it is normal for dogs to experience the occasional upset stomach, or episode of diarrhea, but experiencing severe symptoms, such as bloody stools, may be a sign of something more serious. Inflammatory Bowel Disease (IBD) refers to a group of gastrointestinal diseases that result in the inflammation of the intestines. The exact cause of IBD in dogs is unknown, but bacteria and nutrients normally found in the intestine are thought to be the cause of the abnormal immune response that causes inflammation.