Hyponatremia: a word few dog owners may be aware of. However, it describes a potentially fatal condition that could affect your dog, and even kill your dog. And if you allow your dog to swim, or play with the hose, it is a word you should definitely know the meaning of! It is the reason why we, at Bach Canine Rehab, are a bit weird about dogs having toys in the pool, especially tennis balls. It is the reason we may use a toy only as a lure, and not allow a dog to take the toy off the water line. It is the reason we may, if your dog demonstrates water catching or extreme drinking behaviour in the pool, opt to work in the underwater treadmill where these behaviours can be better controlled. So what is it?

Hyponatremia means low blood sodium levels, and can also be known in this format as water toxicity. It happens when the body takes on more water than it is able to process. This excess of water dilutes the extracellular fluid, causing electrolyte levels, particularly sodium, to drop. The cells then begin taking on more water, to maintain balance between outside and inside the cells, and so begin to swell. As sodium maintains blood pressure, nerve and muscle function, without it, the body’s systems begin to fail. Cells all over the body, including in the brain, begin to swell.

What symptoms does this cause? The dog can seem fine immediately after taking on a lot of water, but his/her condition will deteriorate quite rapidly, and they will show symptoms such as staggering / loss of co-ordination, lethargy, nausea, bloating, vomiting and excessive salivation. If the dog has taken on a lot of water, these symptoms can progress to difficulty breathing, collapse, seizures, coma and death. If your dog displays any of the above symptoms after playing in water, contact your vet immediately.

So what relevance does this have, to us as dog owners, and as hydrotherapists? Dogs can very easily take on too much water if grabbing for toys off the waterline (whether in a pool, lake or pond), or if they like playing with the hosepipe in the garden.

How do we stop this happening? Well, this is why we get weird about toys in the water! And would also suggest that if you throw a ball for your dog to retrieve in a pond or lake on walks, you are very careful about how much, and how often. Tennis balls are particularly dangerous as they soak up a lot of water, which then sprays back down the dog’s mouth as they chew the ball. We would also advise not letting your dog play with the garden hose, especially if they enjoy biting at the spray.

Playing in water can be hugely beneficial and satisfying for your dog, particularly in hot spells – being aware of hyponatremia or water toxicity means you can enjoy the water with your dog, whilst being clued up on the risks!

Don’t just take our word for it: other blogs on hyponatremia: