The symptoms include constant and excessive thirst or drinking, frequent urination, and very dilute urine (eg. it looks clear, rather than yellow). Dogs may also act disoriented, have a poor coat, and may lose weight.
The inability for dogs with this condition to conserve water results in a need for the dog to drink constantly. And because it's constantly drinking, the dog also needs to urinate frequently. Owners may first notice that a problem is present because the dog starts to have housebreaking accidents. Thus the problem is more noticeable in indoor dogs. It's easy to miss the signs if a dog has a ready supply of water and easy access to the outdoors to relieve himself.
Diagnosing diabetes insipidus can be difficult. There are many types of health and behavioral issues that can cause dogs to soil in the home. For example, some health issues that can cause increased thirst and urination include Canine Cushings disease or liver disease. Just plain old age can also cause dogs to need to urinate more often and have accidents in the home.
Because it's so difficult to pinpoint the exact issue causing house-soiling, pet owners should bring the dog to the veterinarian for assessment. The vet can test the dog's blood and urine and may recommend other tests as well.
Sadly, dogs are sometimes surrendered to shelters or even put down because owners consider the house-soiling as a behavior problem!
If you believe your dog may have this disease, schedule a visit to the veterinarian. Tell him what you think and if he doesn't have experience with this relatively rare disease, ask if he knows another vet who does. Depending on the cause of the disease, canine diabetes insipidus may be treatable or even curable in some cases. Other dogs will have the condition for life.