Hello Evelien,
 
I am NOT a vet, but as a shelter volunteer have handled hundreds of
ferrets with varying illnesses.  I am sorry your boy is battling with
cardiomyopathy.  Here we too have walked that path.  With regard to
drinking urine.  This happens when the body begins to crave salts.
This condition is most usually an indicator of an adrenal condition,
understandably as a primary function of the adrenal gland is to regulate
blood sugar and salt levels.  In your ferrets case adrenal surgery is
NOT an option.  Perhaps your vet could look into the lupron treatments?
Please email me direct if I can be of any further guidance.
 
sincerely,
alicia
a ferret friend
[Posted in FML issue 2834]