I have a 9 week old Olde English Bulldog who has had diarrhea for almost a week. I brought him to the vet on Monday he has no parasites everything is normal, they even did a stool test. They put him on Metronidazole twice a day for 6 days. Its now Wednesday and it seems like sometime its getting worse. Should I bring him back to the vet or try new food? He's currently eating Purina Puppy Chow.

I doubt it's the food. Unless of course you changed it on him during this time.

There is a good chance that he has either coccidia or giardia. Both are hard to find in a fecal. Your pup could also have an overgrowth of bacteria in the intestine.

Colitis will cause diarrhea. Antibiotics and a blood test usually help with that.

I think you should go back to the vet. Recheck for parasites.. sometimes just because they don't show in large numbers, doesn't mean that they don't have it. Talk to your vet about colitis.

Just because the first round of antibiotics didn't work, doesn't mean the vet didn't do his job. Sometimes you just have to get more aggressive with the treatment.