Hello & welcome, I am Dr. B, a licensed veterinarian and I would like to help you with your wee one today.
Now as I am sure you can appreciate, just like people, dogs can have diarrhea that is caused by a range of agents. These include bacteria viruses, parasites (worms but also protozoa like Giardia, Coccidia, etc), toxins, inflammatory disease (ie IBD), cancer (a concern at his age), and general dietary indiscretions. With so much to consider, it can be daunting to get to the bottom of which differential is to blame, but if he is well in himself otherwise then you can try to settle this at home for him.
To start, do consider starting him on a light/easily digestible diet. Examples would be cooked white rice with boiled chicken, boiled white fish, or scrambled eggs (made with water and not milk). There are also veterinary prescription diets that can be used in cases of gastroenteritis (ie Hill’s I/D or Royal Canin’s sensitivity). The easily digestible diet will be better tolerated and absorbed by the compromised gut and should get some nutrients in and result in less diarrhea. Also feed this as small frequent meals to further decrease the volume of diarrhea he is producing. As long as improvement is being seen, I usually advise that the diet be continued until the diarrhea is settled, and that they are then slowly weaned back to their normal diet over a week.
Since diarrhea can quickly dehydrate an older dog, even as he is drinking, we need to keep an eye on his hydration. The reason is because no matter how much they drink, we often find that dogs just cannot keep up with diarrhea fluid losses for long (and dehydration is what makes them feel poorly). To check his hydration status to make sure they are not becoming dehydrated there are a few things we can test. One is whether the eyes appear sunken, if the gums are tacky instead of wet/moist, and whether he has a "skin tent" when you lift the skin. To see how to check these parameters for dehydration, you can find a wee video on this HERE. If you are seeing any signs of dehydration already, since he is older, then you do want to have his seen by the vet before this becomes an additional issue for him.
If you are concerned that he is becoming dehydrated, you can try and encourage him to drink but offering fresh water or even low-sodium chicken broth. Furthermore, you can offer rehydration solutions like Pedialyte. Pedialyte is nice (though aim for a flavorless one) because it will get some of those lost electrolytes back into him as well. A typical maintenance rate for hydration in an animal is 48mls per kilogram of weight a day. Of course, his requirement will be higher since we'd have to also consider how much fluid is being lost in the diarrhea. So, if he is drinking well then you don't need to syringe fluids. Still, this baseline will give you an idea to whether he is meeting this target plus matching his own losses.
Furthermore, there are some anti-diarrheals that can be used in dogs to slow things down for their gut if his stools are very runny. As I am sure you appreciate, these would not be a cure (since cures would depend on the culprit and might include antibiotics or anti-parasitics, etc.) but would slow the diarrhea to aid the body potentially absorb more water/nutrients then it would have if the diarrhea were unchecked. Furthermore, these treatments will coat the GI and could just settle the GI upset. In regards ***** ***** options for your wee one, the one we most commonly use in dogs is Kaolin/Kaopectate (More Info/Dose) or Pepto Bismol (More Info/Dose) available from your local pharmacy. Furthermore, Protexin Pro-Fiber (which is available OTC at vet practices; example) would be another option. All will slow diarrhea and the Pro-Fiber has the bonus of providing support to the delicate good bacteria of the GI.
And just to note, while not usually to blame for diarrhea in older dogs, you can consider treating for worms to make sure they are not involved in his diarrhea at all. To treat worms, you can buy worming products over the counter. Therefore, you can ask for them at the vet's or at your local pet stores and these will be dispensed to you. There are a range on the market, but you want to use a good quality wormer that covers both round worms and tapeworms. In this situation, it would be ideal for you to treat him with Drontal, Panacur, or Milbemax as they will cover all the worms in question. Do make sure to have an idea of his weight before purchase wormer to make sure you get the correct dose for his size.
Overall, diarrhea can be triggered by a wide range of agents. Therefore, we'd want to consider supportive care, monitoring, and potentially treating with anti-diarrheals at this stage. If you try this over the next 24 hours and don't see improvement or he is appearing dehydrated, then we'd want to consider getting his vet involved at that stage. If you need to do so, consider taking a fecal sample with you so they can see what is producing and potentially have it tested if need be. Depending on the exam +/- any fecal test findings, you will then be in a position to know if he needs anything prescribed and if so what he needs to clear this for him.
I hope this information is helpful.
If you need any additional information, do not hesitate to ask!
All the best,
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