Altering his diet might help. We are what we eat, so they say. Hamsters do seem to produce a high concentration of calcium in their urine, but I have yet to do some research on this myself. I tend to stick to a dry commercial mix (I feed Burgess Supahamster Harvest and Harry Hamster) together right now and only add Kallo organic wholegrain puffed rice, organic jumbo oats and Buckwheat. He also gets one bonio dog biscuit as a treat and a monkey nut in it`s shell. Fresh food only consist of a piece of apple every few days, a little bit of tomato and that`s about it really.
Calcium content is something I will be careful of aswell. It`s definately worth researching into this if it helps keep conditions like this at bay. Pervention is better than cure...and all that!
Hope he continues to get well katarina. x