First, I am glad to hear that it was only a small amount of blood in his diarrhea. In that case, that is likely to be related to colonic irritation/inflammation and his straining. So, if we can soothe his GI, we'd expect that to settle as well. Though I do have to note that if your lad isn't able to keep water down then we may be in a position where we need his vet to bypass his mouth with injectable anti-vomiting medication to break the nausea cycle.
That said, if we are sure he has not ingested anything harmful and hasn't just vomited, we could try him on an OTC antacid. Often we will use Pepcid (More Info/Dose @http://www.petplace.com/article/drug-library/library/over-the-counter/famotidine-pepcid), Zantac (More Info/Dose @ http://www.petplace.com/article/drug-library/library/over-the-counter/ranitidine-hcl-zantac), or Tagamet (More Info/Dose Here @ http://www.petplace.com/article/drug-library/library/over-the-counter/cimetidine-hcl-tagamet). Whichever you choose, we’d give this 20 minutes before offering food to allow absorption. Of course, do double check with your vet if he has a known health issues or is on any medications you haven't mentioned. Though if he cannot keep that down, then again we'll likely need injectable anti-vomiting medication from his vet to settle him enough for oral treatment.
Though if he can, we can plan to offer small meals of a light/easily digestible diet. Examples you can use are cooked white rice with boiled chicken, boiled white fish, cottage cheese, or scrambled eggs (made with water and not milk). The aim of these diets is that they will be better tolerated/absorbed by the compromised gut. Therefore, it should get more nutrients in and result in less GI upset and less diarrhea. As well, we can also add fiber to this (ie canned pumpkin,all bran) as these can safely bulk up the stool to reduce diarrhea further. As long as improvement is being seen, I usually advise continuing this until the signs are settled, and then weaning him slowly back to his normal diet.
Since dehydration is a risk when they have upper and lower GI signs, we need to keep an eye on his hydration. To check this and ensure he’s not becoming dehydrated, there are a few things you can test. Further to checking for gum moisture, you will want to make sure his eyes are not looking sunken and that he doesn’t have a "skin tent" when you lift the skin. To see how to check these parameters for dehydration, you can find a good video HERE (http://www.ehow.com/video_12232503_dog-dehydrated.html). If you are seeing any signs of dehydration already, then that would be our cue to have him seen before this becomes an additional issue for him (especially as it is often dehydration that makes them feel unwell).
Finally, since the blood was likely irritation induced, you can consider trying a pet safe anti-diarrheal. As I am sure you appreciate, these would not be a cure for infectious issues; but it can still be of benefit. It will reduce diarrhea load, allow the body to absorb more water/nutrients, and soothe the upset gut. In regards ***** ***** options, the one we most commonly use is Kaolin/Kaopectate (More Info/Dose @ http://www.petplace.com/article/drug-library/library/over-the-counter/kaolin-and-pectin-kapectolin-k-p)). This is available OTC at most pharmacies. Otherwise, Propectalin, Canikur, Fast Balance, and Protexin Pro-Fiber (which is available OTC at vets, pet stores, and even Amazon) would be another option. All will slow diarrhea and those last ones have the added bonus of providing support to the delicate good GI bacteria (ideal in quick diet changes). So, these can be used as a short-term means of soothing his upset GI.
Overall, if the new diet was started a bit too quickly in a sensitive stomached dog, then this could be our trigger for these signs. Of course, we'd also have to be wary of brewing gut infections, pancreatitis, or dietary indiscretions. In any case, we’d want to start supportive care to settle his stomach. If he cannot keep that or water down at any point, appears dehydrated already, or doesn’t respond to the above within 12-24 hours; then we'd want to get his vet involved. They can assess his hydration, rule out fever, make sure there is nothing in his stomach that shouldn't be there or any sinister viruses present. Depending on their findings, his vet can treat him with injectable anti-vomiting medication, fluids, +/- antibiotics to settle his stomach, and get him back feeling like himself.
Please take care,
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