Actually there are 2 other elements rarely discussed. I have brought it up on different occasions, but it seems it is still often not mentioned at all. Temperature and pH. One environmental the other diet related.
The solubility of urates changes dramatically with temperatures as they drop below 80°. Below 70° the crystallization of urates is very much greater than at 80°+ When a tortoise not "programmed" to empty its gut for brumation is subjected to lower temperature with higher urate levels - you have a recipe for stones to form much more easily. Or... tortoises fed, and with a full gut, are continutally subjected to lower temperature. A tortoise naturally going into brumation or aestivation empties its gut and has subsequently lower concentrations of built up urea. Natural metabolism while slowing/stopping eating eliminates it.
Increased crystallization also occurs when pH levels stray much higher or lower than neutral (7-8). So a diet that is skewing the natural pH of the gut will also have an effect.
