Hello I am Dr. Joey. Thanks for trusting me to help you and your pet today. I am a licensed veterinarian with over 15 years of experience. I look forward to working with you.
This can be quite frustrating! It sounds like you have an excellent start to determine what is going on. I want to confirm when the stool was tested it was tested not just for standard parasites (including coccidia) but also for Giardia and cryptosporidium. It sounds responsive to metronidazole which gives us some information. At this point if we are sure this is not a parasitic problem, then we need to make sure there is not a medical problem such as pancreatic insufficiency. So, some lab work (cbc, chemistry profile, TLI/PLI, urinalysis) is indicated as well as an x-ray to confirm he did not swallow something (he is a puppy). If everything looks great and he continues to thrive so long as on metronidazole, then this may be a case where the system has become very upset from one inciting incident and needs a few weeks (4-8 weeks) to recover/normalize or that he may have a food ingredient intolerance.
From here out assuming all testing is normal I usually advocate feed a commercially prepared bland diet such as the Royal Canin Gastrointestinal Puppy or HIll's i/d for 8 weeks in addition to using a probiotic (such as Proviable or Fortiflora...remember not all probiotic are made equal; ask your vet for a proper recommendation). The hommade diet is great BUT we run a huge risk for malnutrition at this age if this is fed for weeks on end. This is why the prescription bland diet is important. You can discuss use of metronidazole as needed for the first 4 weeks and then see if it is needed any longer.
I am also assuming that he tested negative for parvovirus infection.
(when I say you can discuss use of metronidazole, I mean discuss this with your vet)
I want to assure you this is not an uncommon problem in younger dogs (the chronic diarrhea after an inciting incident). It is super important, however, to ensure there is not a treatable medical problem which is why all the testing is needed to rule this out first. And most will respond to the bland diet and probiotic with a few weeks. Some puppies need to stay on the bland diet throughout puppy-hood but it is perfectly balanced and designed for growth.
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