What Causes Bladder Stones in Dogs (and how to prevent them)?

Why does a dog develop bladder stones? What are the different causes and does the type of stone make any difference?

In this Dr Alex Answers post I discuss what the different types of bladder stones are, what causes them and how we can go about trying to prevent them and reducing the risk of them coming back in a dog who has already been treated for bladder stones in the past.

Right, so my first question today is, what is the cause of bladder stones in a dog?

So this wee dog, they had a bladder full of stones removed, they were put on a specific diet, they changed to spring water but the same problem recurred very quickly a year later. The vet said that they'd never seen a recurrence so fast and the dog needed a second emergency surgery and the question really is, what is the cause of this?

So we need to break this down.

The causes of bladder stones in dogs

So there are 4 main types of bladder stones and each of those has a different cause. So without knowing which stone it is, it's very difficult or impossible to give an exact cause. And actually, this dog’s stones have been sent off for analysis. They do take some time to come back depending on where you are in the world, that can take a few months in some cases, but that really is the first thing that we need to do.

Different types of bladder stone

Now the most common stone is something called a struvite and that's generally due to an underlying bacterial infection that changes the urines pH, so the acidity and making it become alkaline. It can also be caused by some drugs or diets and it can also form when there's a very concentrated urine as well because what can happen is we can get a high salt urine content and when it's very concentrated, these salts all precipitate out and they form like a sludge or sand and that can then form bigger, larger stones.

Now apart from struvite our next most common stone is something called calcium oxalate and actually these are increasing in frequency. So as we're better able to manage and better able to prevent struvite stones in the first place, we're seeing less of those and an increased percentage incidence of calcium oxalate stones, and actually the cause of these is poorly understood. They form an acidic urine, so unlike struvite which are alkaline, they form an acidic urine and they seem to form in pets that are being fed diets high in calcium, oxalate and citrates. They can also be seen when there is a prolonged antibiotic use as well and that can alter the normal gut flora. So the normal bacteria that are present inside the intestines that then interferes with the general and normal absorption of these salts. So that's the first and second most common bladder stones.

The next two we've got are something called cystine and then finally urate and these are both generally felt to be a result of genetics. So an example of this is male Dalmatians, which are the classic breed to suffer from urate bladder stones, although females and other breeds are also predisposed.

Different stones have different causes

So once we know what the stone is, we can then look to identify the underlying cause.

So if we take struvite for an example, we know that's normally caused by an infection, but why are we getting this infection? So is the animal diabetic for example, are they suffering from a urinary incontinence which can make cystitis more common? So we need to look and see if we can identify the underlying cause, which will then help us to be able to prevent it. Now very often we can't actually find an underlying cause and we need to do a few other things and dietary management is definitely something that we need to consider and that's regardless of stone type.

Preventing bladder stones in dogs

There are different diets that have been shown and proven to reduce the incidence of each stone type. So depending on what type the stones are found to be, depends on what the dietary advice will be. There are things that we can just add to normal diets, for example, that may be able to change the pH, although that may be a little bit more hit and miss.

And then the final big one and general recommendation would always be to try and increase the water intake.

So a lot of these diets will do that anyway, they'll increase the water intake and that acts to reduce the concentration of the urine, which helps just flush out the bladder more frequently. So if you can imagine you've got a lot of salts in the urine, if they're very dilute, they're not going to precipitate out and form that sludge in the first instance. But if they do, then just producing lots of really dilute urine will mean that your pet's going to need to go to the toilet a lot more and they're just going to flush out all of this kind of sand and grit before it develops into big stones. So that's really important when it comes to prevention.

The above is a transcript taken from “The Dr Alex Answers Show”.

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