Hello & welcome, I am Dr. B, a licensed veterinarian and I would like to help you with your wee one today.
Based on Khan's signs, I'd be concerned that this diarrhea is taking a toll on him. The lack of pain and quick recovery when he does go down is more suggestive of weakness due to dehydration and nutrition/energy loss than an actual issue with the back legs.
Therefore, at this stage, I'd advise addressing the diarrhea. Now as you will be aware this can be triggered by a range of agents like bacterial or viral gastroenteritis, pancreatitis, parasites/protozoa infections, general dietary indiscretions, and ingestion of harmful items (ie toxins, plants, non-edible items).
With this all in mind, as long as he has not had access to anything harmful, we can try some home supportive care to try to settle his stomach. To start, you can consider putting him on 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). There are also OTC vet diets that can be used (ie Hill’s I/D or Royal Canin’s sensitivity) too. 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 diarrhea. 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 real risk here, 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. 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 and weak).
Just to note, if you did think he was struggling to remain hydrated, you can try encouraging him to drink. Offer fresh water but you can also use lactose free milk or low salt chicken broth. Or if he is drinking poorly, you can syringe feed fluids at a rate of 48ml per kilogram of his weight per day (of course broken down into multiple offerings). Ideally, you'd want to use an OTC pet electrolyte solution (ie Lectaid, Resorb) or at least a pediatric electrolyte solution.
Finally, as long as there is no blood in those stools, 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. So, these can be used as a short-term means of soothing his upset GI.
Overall, a wide range of agents could trigger the diarrhea and weakness we are seeing. Therefore, in his case, we’d want to start supportive care to settle his stomach. If he cannot keep that down, 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 infectious agents present in his stool. Depending on their findings, his vet can treat him with injectable antibiotics and supportive care to settle his stomach and get him back feeling like himself.
I hope this information is helpful.
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All the best,
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