There's nothing more discouraging than letting your dog out of her crate only to find that she's peed in it. Whether you have an older puppy who has not "gotten it" yet or an adult who is still unreliable in her crate, there may be several explanations for your dog's accidents in the crate. With time and patience, your canine can enjoy her time in a clean, dry crate.
Crated Too Long
The most common mistake in crate training is leaving a puppy too long, too soon in her housebreaking training. Puppies' bladders can only "hold it" for about an hour per month of their age, up to 6 months. For example, an 8-week-old puppy may be crated for 2 hours before he'll need a potty break. Some small breed adult dogs and even some larger breed individuals might not be able to hold it as long as you might think -- this is where you need to understand your individual dog's bathroom needs and habits.
Crate Is Too Large
Your dog's crate should be big enough for her to lie down, stand, and turn around comfortably. If the crate is too large, your dog may use one side for sleeping and the other for elimination. A crate should not be used as a containment pen, so it does not need to provide room for anything more than resting.
When crate training your dog or puppy, it's important to keep training sessions positive. Never use crate time as punishment or as a "time out" for your dog -- time in her crate should always be peaceful and positive. If your dog is upset or afraid when she is put in her crate, she might eliminate out of fear. Offer your pup a treat when she enters her crate and give her a tasty, safe chew toy to keep her occupied.
Many dogs suffer from separation anxiety, an excessive fear of being left alone. Dogs with separation anxiety commonly eliminate or develop other destructive behaviors to cope with their fear. Extreme separation anxiety needs to be addressed by an animal behaviorist, since in may require medication; however, mild generalized anxiety may be addressed by a professional dog trainer skilled in desensitization training. Leave your dog in her crate for just a few minutes at a time while you are still home to begin to desensitize her from fear of being confined.