It's unfortunate but common for our pets get dog diarrhea, and the causes may be a diverse variety of reasons.
Commonly, it's an up-set stomach from something ingested not agreeing with our
pet that causes digestive problems, but other more severe cases should not be taken lightly.
Perhaps the best way to get an idea of how your dog's digestive tract is doing is by simply looking at it's stool during your daily clean-up. You don't have to get out a magnifying glass, just note the firmness and take action if you suspect issues.
Common reasons for diarrhea:
rapid change in diet (always change a dog's brand of food gradually over a period of one or two weeks) Even a slight change in protein such as chicken to turkey may cause issues.
eating garbage/fatty foods and or human foods not tolerated by the dogs digestive system. (also see foods harmful to dogs)