Very interesting topic that seems to trigger different answers and recommendations as to what is 'normal' or 'good'.
I believe urates are a necessary part of metabolism and should always be present in a healthy animal. I would think the quantity would be a by product of the quantity of certain food types, proteins in particular, in the diet. Other things like oxalates also seem to contribute and will dramatically increase the production of uric acid. This is all eliminated from tortoises in the form of the white urates we talk about. That is really uric acid.
In reptiles and birds, "urates" is really uric acid. That is the more evolved form of uric waste produced in animals. The simplest way to eliminate the nitrogenous waste which is produced in the metabolism of purines, is to simply eliminate the ammonia produced in its simple earlier stage. This is toxic and only animals like fish that immediately can eliminate this into water do it that way. In mammals, the ammonia is further converted to urea which is water soluble but can be toxic, so must be eliminated regularly, and done so through urine mainly. The more metabolic intensive version is to further convert this to uric acid. This forms a paste or solid compound that can be eliminated without the need for water. Birds and most reptiles do this.
So it is all the process and an "end product" of metabolism. A healthy tortoise should eliminate urates. How much will depend upon diet. Higher protein diets will produce greater amounts of purines. Those are the key building blocks of growth and nucleic acids. So that is an essential item! Surpluses are converted to ammonia and so on... Oxalates are known to increase uric acid production. In tortoises, these are simply eliminated.
So no matter how much water, or how well hydrated a tortoise is, should only have the effect of increasing water releases and should not effect urate levels. Diet content would do that. Many studies are showing that gut Ph can effect how solid the urates are and a low ph and high sugars facilitate crystallization.
So, food for thought. And a bit contrary to a lot of the advice we give!
@deadheadvet This is one I had thought of you about. I would love your thoughts on this as there is so much about too much urates being bad and well hydrated means no urates. But that doesn't seem to quite fit with me.