Hi, I'm Dr Steve. DId your vet tell you what type or name of the stone or sedimment?
Bladder stones can have different compositions. SOMe are dissolvable with special foods and some are not dissolvable. In my experience most dogs have stones that are struvite which is the dissolvable kind.
What diet is she on and how long has she been on it please?
The diets help to slowly shrink the stones. The sediment could be from dissolving of larger stones or it could be the formation of new stones. If the stones are of the dissolving kinnd like struvite, then again in my experience I have not had a dog that didn't improve with the proper diet.
So I am clear, the original stone passed 2 months ago was not sent in to see what it was made of, but the sediment recently passed has been sent in for testing?
With her being on the C/D for 2 months makes it unlikely that teh sediment is new sediment because the C/D is designed and effective at preventing the formation of new stones so the sediment is probably coming from the breaking down or dissolving of the old stones. So it sounds like the diet is working and that she is making progress.
It seems unusual that it wouls take this long to get results from a stone that was sent away 2 months ago. You may need to have your vet check again with the lab. IN the US , I usually get results from stone analysis within 7-10 business days. Your vet may want to check that the stone actually made its way to the lab and that it hasn't been "lost" . If the lab can not locate the stone yo may need to continue watching for sediment and send in another sample to confirm that you are on the right track. From our discussion it sounds like you are on the way.
C/D is actually designed to prevent new stone formation so it is not likley these are new stones, at least not the struvite type that c/d does dissolve.
Nw another thing to be concerned about is that if the stones are calcium oxalate stones, which are not dissolvable, then the story changes. This is why it is important to know what type the stones and sediment are. I am not trying to worry you , but I do want you to know all of the possibilities and your options.
Another ultrasound at this point will only tell you if she ha stones and the sediment indicates that there are still stones in some degree of forming or dissolving. The analysisi of the original stone or of new sediment will give more useful information. The ultrasound in another 4-6 months is a good idea to make sure all the stones have been dissolved, but knowing if it is a dissolving stone will make you not have to be as concerned for the next 4-6 months.
Other than the lab taking so long, it sounds like your vet is on the right track as well. I hope this has helped explain the progress of stone dissolution. If it has would you please click the submit button so i may receive credit for my answer. If you have more questions, please continue. I will be checking in throughou the day in case you think of more questions later. Thanks for using justanswer and good luck.