took Callie to the vet the other day for her allergies, and also because she has been peeing on the carpet... the vet gave us some ideas for her about the peeing but also took a urine sample... and called yesterday, said Callie has blood in her urine, not visable blood but abnormal amounts of red blood cells. they think maybe she has stones, and are going to do a radio-graph, have to bring her in next wed early morning, and she can't have anything to eat before...

Im kind of worried about this, has anyone else had this happen to their cats? is it serious?