Illness and worms can cause this. If she is an older dog,this can simply be a sign of aging. It sounds like you want to speak to a vet.
A sudden irreversible cardiac arrhythmic event which causes sudden death (in both females and males). If the question is made more specific (such as regarding STDs) then a more relevant answer can be provided.
Slaughter.
Asphyxiation
Some symptoms of an overactive bladder can include: a sudden urge to urinate which is difficult to control and urinating frequently (usually more than 8 times in a single day).
There are several causes of sudden water retention. Poor circulation, premenstrual symptoms, salt, or a blockage in the lymphatic system can all cause this condition.
Swim bladder damage can usually be traced back to either poor water conditions or sudden trauma such as a large variation in their water temp or bruising from some external force.
a surge of testosterone in males and it causes ovulation in females.
Ingesting Ipecac
testosterone
Improper diet
A shock is something which causes sudden, heavy impact, a sudden electrical charge, or an amount of considerable emotional impact.
I would ask your vet but that sounds like Parvo