Struvite Crystals!!!  Has anyone ever had this happen to their cat?  Ughhhh, we went through this horrible disease with our male cat Buster.  After several trips to the Vet and finally getting PU sugery, I am happy to say he is doing well.  If you have never heard of struvite crystals, cats get them from their diet.  Mainly too much magnesium in their food. Their PH level is off forming crystals.  These tiny crystals block them and the cat cannot relieve themselves.  If not caught early, this is fatal to cats especially to males.  Keep a close eye on your cats to make sure they are going to the bathroom and not grooming themselves excessively in this area.  Other signs are going outside of the litterbox, trying to go to the bathroom every couple of minutes, crying when they are going to the bathroom.