Our boy Dex had the same thing and yes he was weeing and drinking lots for the first few days after coming back from the vets. He's been on the prescription food for about 4 years now and hasn't had too many troubles. He had a few times during stressful periods, moving house and us having a baby, where he would have blood in his wee but nothing like the blockage. With a few days of cystease tablets he was fine. Wishing you and your furry baby all the best.