- The dog/cat/ferret/etc ingested something potentially toxic, like chocolate, rat poison, ibuprofen, Tylenol, or an entire bottle of Rimadyl chew tabs. Especially in cases where there is known ingestion, pets should always be seen as soon as possible to have vomiting induced. Some people think it's better to wait and see if their pet starts showing clinic signs of toxicity, like vomiting, not acting right, etc, but some toxins can take days or weeks to show their full effects. Rat poison can cause bleeding into body cavities that wouldn't be noticed by the owner until the pet is severely anemic. Ingestion of Tylenol can cause irreversible liver damage that might not make a pet clinically ill for several days. It's always better to get the toxin out by induction of vomiting and try to absorb as much of the remaining toxin by administration of activated charcoal than it is to take a "wait and see" approach.
- The pet is seizuring. I'm not sure why owners seem to panic over vomiting and diarrhea but don't seem to be as concerned by seeing their pet have a seizure. We get a lot of phone calls asking if a seizuring pet should be seen right away. Seizures that end quickly generally don't cause much damage (aside from making the pet disoriented/distressed and possibly injuring themselves by falling into or off of furniture, or biting their own tongue). Seizures that are prolonged can cause significant brain damage and other organ damage as the body because hyperthermic. There is no way to know if a seizure is going to be a solitary event or if it will become a pattern. Observation at a clinic is important so that, if your pet begins seizuring again, the seizures can be stopped immediately. There are a lot of underlying causes for seizures, so a thorough exam is important to try to determine why the pet started seizuring in the first place.
- Cats who can't urinate. Oftentimes, owners mistakenly think that a cat who is straining in the litterbox is "constipated", when in reality, they are straining to urinate. Cats- especially male cats- can develop blockages in their urethra that completely obstruct the flow of urine. Their bladders can fill to the point that they ultimately die of severe electrolyte abnormalities or bladder rupture. A typical (unfortunate) scenario is that an owner sees their cat straining in the litter box in the morning, leaves for work, and comes home to find a dead cat. Urethral blockage is extremely painful and should be addressed immediately.
- Multiple episodes of vomiting in a short period of time, vomiting blood, projectile vomiting, or unproductive retching. Little stomach bugs or a single episode of dumpster diving cause vomiting, but typically not vomiting with the above signs. When we see these signs, we start to worry about problems like foreign body ingestion, gastric ulceration, parvovirus infection in puppies, or GDV (especially in large, deep-chested breeds). This is not "wait and see" sort of vomiting- vet examination ASAP is indicated.
- Exotic pets acting abnormal in any way. Aside from ferrets, almost all exotic species are prey animals that are hard-wired to never show signs of disease or injury. If these animals go off of food, start sleeping more than normal, stop vocalizing (if it's a bird), start vocalizing (if it's a small mammal), hide when they would normally be active, or do anything out of the ordinary, it could well be a sign of disease. Often, by the time you can obviously tell there is something wrong, exotic species are severely compromised. Better safe than sorry with exotics!
- Pets who have been hit by a car or attacked by another animal. Even if it doesn't look like there are any injuries, many severe internal injuries don't make themselves known right away. Splenic rupture, bladder rupture, or penetrating wounds into the chest are all examples of wounds that a pet owner might not notice, but that could ultimately become fatal. Cats in particular are masters at hiding severe injuries until they decompensate. Don't wait until pets show signs of injury after major trauma- have them evaluated as soon as possible to give them the best shot at treatment and recovery in case there are some hidden injuries.
And it's always a good idea to have a pet emergency fund (or pet insurance) squirreled away should you need it! Emergency vet visits ain't cheap :-/