If Fido is suddenly consuming an excessive amount of water and always appears ravenously hungry, he needs to visit the vet for an examination and testing. Excessive water consumption, formally known as polydipsia, is usually accompanied by polyuria, or excessive urination. Constant hunger in a well-fed dog is called polyphagia. Both symptoms separately result from various conditions, but a dog exhibiting polydipsia and polyphagia is often diagnosed with either Cushing's disease or diabetes.
Polydipsia and Polyuria
Excessive drinking and urination are often symptoms of kidney or liver disease, or indications of diabetes mellitus. Other causes include high blood calcium levels, or hypercalcemia, which can be a sign of cancer; increased thyroid levels, or hyperthyroidism and hormonal issues. In intact female dogs, polydipsia and polyuria can result from a potentially deadly uterine infection known as pyometra. If your vet prescribes a diuretic for your dog, as often occurs in congestive heart failure, excessive drinking and urination are common side effects. The same holds true for canines receiving steroid medications.
Your vet conducts blood tests and a urinalysis, as well as X-rays, to determine the cause of your dog's polydipsia. Treatment depends upon the diagnosis.
Many dogs won't refuse an opportunity to eat, no matter how well-fed they are. Polyphagia goes beyond normal canine greed and often occurs in older animals. Dogs with an insatiable appetite may also exhibit polydipsia and polyuria. While most cases of polyphagia have an underlying physical cause, it's possible that a behavioral or psychological problem is the culprit behind the constant hunger. Physical issues include exocrine pancreatic insufficiency, certain cancers and inflammatory bowel disease. Steroid medications can cause polyphagia as well as polydipsia.
Your vet conducts many of the same tests as for polydipsia, along with an endoscopy to biopsy the stomach and small intestine. Treatment depends upon the diagnosis. If it appears the polyphagia is psychological in nature, your vet might recommend dietary changes and more frequent feedings.
Canine Cushing's Disease
If your dog is diagnosed with Cushing's disease, also known as hyperadrenocorticism, that means his adrenal glands are producing too much cortisol hormone. Other symptoms include hair loss, skin infections, skin thinning and bruising, frequent panting, lethargy and abdominal enlargement -- development of a potbelly. In the adrenal-dependent type of the disease, a tumor grows on an adrenal gland. Surgical removal usually cures the condition, as long as the tumor has not spread. Because many dogs with this type of Cushing's disease are elderly, many vets choose to treat the problem with medication rather than surgery. The more common type of Cushing's disease, pituitary dependent, is treated with daily medication. The polydipsia and polyuria generally stop within a few weeks of starting treatment.
Canine Diabetes Mellitus
Diabetes mellitus, or sugar diabetes, occurs when the pancreas can no longer manufacture sufficient insulin, a hormone regulating sugar levels in the bloodstream. The primary symptoms of diabetes in dogs are polydipsia and polyphagia, along with weight loss. Some dogs develop cataracts. Once diagnosed with diabetes, your dog will require insulin injections given one or more times a day. You must also feed your dog right after giving him the shot. Your dog requires regular visits to the vet for monitoring and possible changes in the dosage level. If your diabetic dog is overweight, your vet might recommend a diet.