How can a pet owner tell if a pet isn't feeling 100 per cent? What signals an emergency, and what signs allow you to wait a day or two before taking your pet to the vet? Jane Gray, a veterinary surgeon since 1989 and deputy director of veterinary services at the SPCA, says the most important signal for knowing if your pet is sick is to know what is normal. 'Give your dog or cat a good stroke for any lumps or bumps. Look into the ears for unpleasant smells, lumps of wax or any discharge. But a little discharge from some animals is normal,' she says. She suggests looking for abnormalities, including for more subtle signs that may surface over three to four days. 'It's really important to understand the disease process because some can be sudden, others very slow and can range from increased drinking to reduced eating. Drinking more may indicate kidney disease or it may mean it's a hot day and they need a big drink.' If your dog or cat stops passing urine for 12 to 24 hours, they may have a urinary blockage, kidney failure or bladder stone. Dr Gray says blockages are common in male animals especially male indoor cats. 'I see a few cases every week and they are medical emergencies. If you don't release the blockage, the bladder will burst and the animal will die.' Dr Gray says dog and cat owners should look at their pet's gums to see if they are dry or pale, which might indicate dehydration or anaemia. If gums are blue, it may indicate a respiratory problem or a lack of oxygen from a heart or lungs. Normal gums are pink and moist. Another medical emergency is gastric torsion, common in large-breed dogs such as golden retrievers and Irish setters. It is a life-threatening disease that causes the stomach to become excessively swollen and twisted within a few hours, and feels tight to the touch. The dog may also try to vomit, but nothing will come up. 'If the tension isn't released in one to two hours, or a maximum of four hours, the animal can die of toxemia [toxic substances in the blood],' she says. 'I can't stress enough that if you are in doubt call your vet. Some owners think an illness will just go away. Always ask first and get some advice.'