Hello, I am sorry to hear that your puppy has stones in his stool. That means that he has definitely eaten something he should not. The real concern is if he has eaten enough that they are causing an intestinal blockage. That would lead to vomiting, poor appetite abdominal pain and tenseness as well as a fever if the blockage is present long enough.
To try and settle his stomach today you can try either:
1) Pepcid-ac (famotidine) at one 10mg tablet per 20 to 40 pounds of body weight
every 12 hours.
2) Prilosec (omeprazole) at one 10mg tablet per 20 to 40 pounds of body weight
every 24 hours.
These will reduce stomach acid and should help settle his stomach.
In this case we need to try and hope that we can get these pebbles to pass through his gastrointestinal tract.
A couple hours after the acid reducers I recommend starting with a vaseline sandwich. Take a slice of whole wheat bread, slather with vaseline as you would peanut butter on a slice of bread, cover with a second slice. Feed it to him piece by piece or he will make a huge vaseline mess. This adds fiber and hopefully makes the pebbles slip through the intestinal tract rather than catch.
For the next few days, until the stones pass, he'll need to be fed a bland diet with lots of fiber added in small meals several times a day, 4 to 6 meals is ideal. We do this so the stones are surrounded, the gut isn't irritated any more and isn't contracting on just rock.
A homemade diet for this is 1/3 boiled hamburger or white, skinless chicken, all fats and juices drained and 2/3 white rice. Add 2 tablespoons of canned pumpkin, not pie filling, just pumpkin, to each meal for fiber.
You'll need to check his stools frequently for stones in the next few days.
Signs that things aren't going well, and he needs an immediate veterinary visit, are continued vomiting even with the acid reducers, a tense painful belly, lack of an appetite, a fever (more than 103.5F rectally) and lethargy.
If you aren't seeing more pebbles in the next day or two a veterinary visit and an abdominal radiograph to see where the pebbles are is option. If it doubt at all that things aren't going well it is always best to have him checked.
Once the pebbles are passed and he's feeling well then start mixing in his regular food, adding a little more regular and less bland at each meal. It should take a week to get him converted back to regular food.
Let me know if you have any questions.