Get Your Dog Care Questions Answered by Experts
If you are seeing black, tarry stools, this indicates that there is a bleed high up in the intestinal tract. This can often be caused by an ulcer or esophageal reflux. If this is the case, your vet might want to prescribe an antacid to help like tagamet.
Your next step should be a scope of the throat/digestive tract if all other medical management methods have failed.
Let me know if you have more questions about this.
I do think that this would be a good idea. Talk with your vet and get a referral or see if he has other suggestions.
Before you talk with him, be sure and write down your questions so that you won't forget anything!