At Barkibu, we receive lots of consultations about digestive problems, especially diarrhea and vomiting. It is very common to talk about colitis in dogs when we talk about diarrhea, but there are not synonymous.
Most likely, your dog has had diarrhea at some point in his life. In the majority of cases, that your dog has diarrhea is nothing to worry about and it will be cured by itself. Still, when your dog has diarrhea it might be inconvenient for both of you.