3. Signs of severe pain or obvious distress
Bring your kitty to an emergency vet immediately if you notice this one. Pain itself always warrants treatment, but it also can be a sign of more serious problems such as urinary obstruction (see above) or aortic thromboembolism (see below).
Symptoms of pain and distress include vocalizing (howling), panting, hiding and overreacting to contact a painful area.