Loki is about fifteen years old and some kind of siamese mix. He has now gotten into the litter box three times to poo and screamed with no resulting elimination. The vet did blood work and took x rays yesterday and tells me there are no signs of constipation, and his blood work is excellent for his age. They told me they put a thermometer pretty far up his rectum and there was no poo in there. This morning we had a screaming repeat of trying to poo and no results/ Any ideas. I know it is not a bladder issue as his urinalysis was clean and i am way familiiar with crystals as y other feline has had struites for years and finally had his penis removed. Loki is peeing freely just not pooing! Help.