My pet is always thirsty: what’s the problem?

My pet is always thirsty. She drinks wherever she finds water, even from the pond and my glass.

If dogs or cats are emptying their water bowls quickly or searching for water at places they don’t usually, such as the swimming pool or outside pond, they are most likely experiencing ‘polydipsia’ or excessive thirst. This is often a symptom of an underlying condition or disease.

My pet is always thirsty: but what’s normal?

We estimate the normal amount of water intake to be somewhere between 40ml and 60ml per kilogram of body weight per day. This can vary if it is a particularly hot day, or if your pet has exercised more than usual. Intake is considered more than usual if your pet is drinking more than 100 ml/kg /day. Polydipsia may also appear with other symptoms such excessive urination.

Why is my pet always thirsty?

Water intake is closely monitored and controlled by the body through a special water regulation cycle involving a hormone released by the brain and sent to the kidneys. Think of this as the manager of a factory that sends a message to workers telling them when there is too little or too much stock. If there is too little stock to meet demand, the factory must produce more, and if there is too much, the factory needs to slow down or get rid of some stock.

Basically, water is taken in by drinking, the body uses what it needs and what is left over is discarded via urination. When your pet has a shortage of water due to the lack of water intake or excessive water loss, this will activate the pituitary gland in the brain (the manager of the factory). The pituitary gland will release ADH (Anti-Diuretic Hormone) that will tell the kidneys to conserve water (suck as much of it up as possible for use) and what is left over is a small amount of concentrated, dark yellow urine. The knock-off effect of this message will also activate the thirst centre in the brain that enhances your pet’s urge to drink more water.

Increased drinking can either occur due to the concentrating mechanism failing because the kidneys are faulty (the workers are incompetent) or because the kidneys do not respond to the ADH (the workers ignore the manager), the hormone is not produced or released (the manager is incompetent), or there is an excessive stimulation to drink more water.

The loss of concentrating mechanism in the kidney or failure to respond to the ADH can occur for many reasons, for example: kidney damage, liver failure and diabetes mellitus.

The body could also fail to release the ADH due to brain damage, infection or cancer.

We also get a condition called ‘psychogenic polydipsia’. This is an uncommon behavioural condition that causes dogs to drink more water.

Some dogs want to drink more water after having a dry meal or food that is high in salt. This is normal. Some medications, like cortisone, can also cause animals to drink more water than usual.

What will my vet do?

Firstly, your vet uses what is called ‘signalment’. He or she will consider the breed of the pet, the age, it’s gender etc. Some breeds are at higher risk of certain diseases, and age-related diseases are relatively common. Small terrier breeds, for example, are predisposed to certain endocrine diseases like Cushings, where the body produces too much cortisone.

Your vet will then take a look at your pet’s medical history:

  • Where there are any behavioural changes in addition to the excessive drinking?
  • Is your pet peeing more than usual or in odd places?
  • Does your pet pee voluntarily or does it leak out while he is sleeping?

These questions are key to helping your vet determine the cause of the problem.

Routine blood tests and urine analysis are key to ruling out common ailments like kidney failure. Other tests might include ultrasound of the liver, kidneys and adrenal glands. Your vet may also perform a water deprivation test where water is withheld for a significant amount of time and the urine tested before and afterwards in order to determine whether the urine is concentrating or not.

What treatments are available?

That largely depends on the underlying cause of the problem. If the cause of excessive thirst would be kidney failure, having ample amounts of water available at all times might be part of the treatment. There are medications and disease-specific food on the market that will help alleviate the symptoms of kidney failure in cats and dogs.

Please ask your vet to advise you about these treatment options.

Article by Dr Tiaan Visser, Cottage Vet



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