Accident
Deep wounds, injuries and significant bleeding
Swallowing objects or choking
Eating toxic/harmful substances (e.g. raisins, rat poison or antifreeze) 

Collapse
Serious trauma (e.g. car accidents)

Behaviours
Breathing difficulties/seizure and fitting
Inability to urinate (especially in male cats)
Severe vomiting or diarrhoea (five or more episodes in a 12 hour period or if blood is present)
Inability to stand or dragging legs
Swollen abdomen or retching (especially large dogs)

Others
Eye problems
Struggling to give birth (such as green, bloody or brown discharge)