To start, have them skip a meal to rest their system and give it a chance to clear out. The more you send in, the more the body must rush to hurry it out if in fact it is battling something (bacteria, viral etc.)
After skipping a meal (you can feed just chicken broth to keep them well hydrated), then start with a bland, cooked meat - usually chicken or ground turkey is best and canned pumpkin. You want to start with pumpkin - which is high fiber - to see if this firms them up or makes the body flush harder. This helps to indicate what is going on, since if it is bacterial, it will feed on the fiber and flush more (translate: faster diarrhea). If it firms them up however, then it isn't bacterial - and potentially viral. Either way, there is inflammation in the intestinal lining and this must be healed before stool will return to normal.
You should stick with this diet for at least a solid 10-14 days to heal the GI Tract. I also recommend a couple of Standard Process supplements that you can get from a vet: Gastrex and Okra Pepsin to help clean them out and heal the lining. I also use Digestinol for healing.
If you have one of those vets who just prescribes something to falsely firm them up (so you feel better, but they don't) such as Flagyl (metronizadole) - save your money and skip it. This just masks the symptoms and does not treat the problem at all. The bacteria, or virus, or inflammation must be treated. Stool is a product of that and merely a symptom, so remember that the stool is not what you are treating.
By the way, I am hearing of a lot of this this summer - something viral has been going around where I live and a lot of dogs got the runs until it resolved.
Good luck!
