Dog diarrhea can be treated by keeping the dog away from food sources for the first 12 to 24 hours, giving the dog access to lots of water and visiting a veterinarian for possible fluids or other serious treatment if the dog is vomiting, lethargic or has bloody feces. If the dog has any of these additional symptoms then the diarrhea may be a symptom of a much larger problem and if the diarrhea is black, then the dog should be brought to the emergency vet immediately.
Diarrhea that is black is usually an indication that there is internal bleeding, which if left untreated can kill the dog within hours. It is also possible for a combination of bloody diarrhea and straining to mean that the dog has a blockage in the stomach and will require immediate surgery. If this is the case, do not hesitate to bring the dog into the veterinarian.
Diarrhea happens most often in dogs when they eat something that does not agree with them or if they have a virus. It can also happen if they have an allergic reaction or have an internal parasite. Most of the time, the symptom is not life threatening but, in some cases, it is a sign of something more threatening such as kidney disease, liver disease or cancer.