What causes bladder stones in dogs and how can they be prevented?

5 years ago

A Tibetan Terrier laying outside on the grass beside its water bowl

Hi Anne,

There are 4 main types of bladder stones in dogs and each of those has a different cause. Without knowing which stone it is, it’s very difficult or impossible to give an exact cause. I am happy to hear your dog’s stones have been sent off for analysis as this is one of the first things we need to do.

The most common stone is something called a struvite and that’s generally due to an underlying bacterial infection that changes the pH of the urine and makes it become more alkaline. It can also be caused by some drugs, diets and when the urine is very concentrated 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 stones in dogs our next most common stone is something called calcium oxalate and 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 the cause of these is poorly understood. Unlike struvite, which are alkaline, they form an acidic urine and this occurs in pets that are being fed diets high in calcium, oxalate and citrates. They can also be seen when there is prolonged antibiotic use as well and that can alter the normal gut flora which interferes with the general and normal absorption of these salts.

The next two types of canine bladder stones are cystine and urate and these are both generally felt to be a result of genetics. For example, male Dalmatians are the classic breed to suffer from urate bladder stones, although females and other breeds are also predisposed. Once we know what the stone is, we can then look to identify the underlying cause.

If we take struvite for example, we know that’s normally caused by an infection, but then we have to look into why we are getting this infection. Is the animal diabetic? Are they suffering from urinary incontinence which can make cystitis more common? We need to see if we can identify the underlying cause, which will then help us when it comes to preventing bladder stones in dogs. Very often we can’t actually find an underlying cause and as a result more diagnostic tests are needed as well as taking into consideration dietary management regardless of stone type. There are different diets that have been proven to show a reduction in the incidence of each stone type. Therefore, the dietary advice will depend on the type of stone they are found to be. There are also things that we can add to the diet that may be able to change the pH, although this may be a bit more hit and miss.

My final and general recommendation would always be to try and increase the water intake. A lot of these diets will do that anyway as they act to reduce the concentration of the urine which to helps to flush out the bladder more frequently. For example, imagine if you’re diluting urine with a high concentration of salt. Eventually the amount of salt in the urine will become very dilute and it’s not going to precipitate out and form that sludge in the first instance. If the sludge does form, then 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. Therefore water intake is really important when it comes to prevention.