The diet is only available through vets....I would not risk feeding any other diet than recommended by your vet....however, the true concern here is that they still have not determined what type of crystals or even IF crystals are a concern. If you can't get the IVD from another vet in town, then ask your vet for a suitable alternate veterinary prescription diet.
As for the urinalysis vs ultrasound....I would suggest a urinalysis first to see if there are any changes from the last, and to see if they can properly find any crystals, and if so, if they can properly identify them. If no crystals are found, and if no bacterial infection is determined, then I would suggest an ultrasound only in the event this problem is not resolving, as in, Einy has trouble urinating, has blood in the urine, or is not producing enough urine, or any other direct problems with the urinary tract and ability to produce urine normally on a daily basis. In that event, then an ultrasound could help detect inflammatory problems, stones not detectable on urinalysis, etc.
If you're not comfortable with your vet's approach, don't hesitate to see another vet entirely.
Cystitis, bladder obstruction
Re: Cystitis, bladder obstruction
..........Traci
Re: Cystitis, bladder obstruction
Thanks, Traci. I will let you know how the checkup goes tomorrow.