This can be normal for your pet to not defecate as your pet has been fasted from the night before surgery. Additionally, we give strong pain relief medication (opioids) which can cause constipation and the anaesthetic drugs can increase the time the intestinal system takes to process food. Unless there is straining without any defecation occurring, we do not worry about lack of defecation unless it is persisting longer than 3 days in which case visiting your regular vet is recommended. Your pet should be urinating as we maintain their hydration on intravenous fluid therapy whilst they are in hospital. In cats, no urination is a cause of concern, particularly if your cat is going to the litter box, straining and no urination is occurring. If your cat is showing signs of non-productive straining to urinate or defecate, this can be an emergency, and we recommend you seek veterinary attention as soon as possible.