Very helpful information. Thank you. Great initial therapy and excellent to deworm as a just-in-case.
It is time to reassess what is going on. Most dogs with hemorrhagic gastroenteritis (HGE) only have it once and not have a relapse in a week. That makes HGE highly unlikely to be the cause. It is important to do a bit more testing today and try to narrow down the cause. And, unfortunately, it also sounds like she needs to be seen again today for therapy. I would highly advocate repeating a chemistry profile with electrolytes (we need to check her pancreas, liver, kidneys and screen the electrolytes for Addison's disease although some dogs do not yet have the electrolyte problems that come with this disease and only the corticosteroid part; so if the ER vet finds her to have a low heart rate then screening for Addison's would be important). As well, not a bad idea to do a repeat X-ray to confirm nothing has shifted to now reveal an obstruction. A complete blood count (CBC) can also be useful to confirm no bleeding issues (low platelets, anemia) and screen the white blood cells for types of inflammation.
Cancer is certainly possible but rarely causes such sudden onset vomit/diarrhea. It is usually more slow in onset with weight loss, and if this was the cause I would not have expected such a dramatic and good improvement for so many days. Most dogs with serious cancer to cause these symptoms would remain with low appetite, lethargic, etc.
So, bot***** *****ne is she needs to be seen today, especially with the bloody diarrhea. However, if she is otherwise doing great (eating, drinking with good attitude) and you think you can hold out to see your regular vet then that might not be bad to get that second opinion. Most ER vets are quite good at working through tough issues like this, though.
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