How common are bladder stones in dogs? 

Bladder stones in dogs are a surprisingly common health issue that many pet owners may not be aware of until their dog begins to show painful symptoms. These stones (medically known as uroliths or urinary calculi), can affect dogs of any breed or age, although some are more prone than others. This article explores what bladder stones are and just how commonly they occur in our canine companions. 

What are bladder stones? 

Bladder stones are solid mineral formations that develop in the urinary bladder. Normal urine is comprised of different minerals as waste products from the body. These stones form when the minerals normally dissolved in urine clump together and solidify. Over time, they can grow into stones of varying sizes—some as small as grains of sand, others as large as pebbles. Ouch! 

How do I know if my dog has bladder stones? 

Bladder stones can be slow to form and there may be no external signs initially. Over time, as the bladder lining becomes inflamed and painful, the dog will start to show signs such as: 

In severe cases, the stones can block the urethra completely, stopping your dog from being able to urinate at all. This can quickly lead to a potentially life-threatening condition that requires emergency treatment. 

Why do bladder stones form? 

Bladder stones usually form due to a combination of genetic, dietary, and environmental factors.  

It is important to note that urine crystals are different to bladder stones. Urine crystals are a common finding in normal dogs’ urine and can be present with no associated problems. It is when these crystals aggregate together to cause stones that the problems begin.  

Factors contributing to bladder stone formation include: 

Types of bladder stone 

There are several types of bladder stones, each formed from different minerals and under different conditions. The most common types found in dogs are: 

1. Struvite stones 

Struvite stones are the most common bladder stones we see in dogs, and they can occur in any breed. They are smooth, pebble-like stones and can grow quite large, sometimes several centimetres across.  

Struvite is made up of three minerals – magnesium, ammonium, and phosphate. Struvite stones often form in association with urinary tract infections from bacteria such as Staphylococci or Proteus species. The infections themselves are usually easily cleared with a course of antibiotics, but the bacteria produce an enzyme called urease which increases the pH of the urine (making it more alkaline). This change allows struvite crystals to form, and over time the formation of struvite stones can occur.  

2. Calcium oxalate stones 

Calcium oxalate stones are also relatively common in dogs, and small breeds such as Miniature Schnauzers, Yorkshire Terriers and Shih Tzus seem to be more likely to develop them due to a genetic predisposition. High levels of calcium in the urine can also lead to these stones forming, and this may be due to an underlying kidney or bone problem. They tend to form in more acidic urine.  

3. Urate Stones 

Urate stones form when there is a high level of a biochemical called uric acid in the urine. These stones are commonly seen in the Dalmatian breed (and to a lesser extent English Bulldogs) due to a genetic mutation which stops their bodies from breaking down uric acid. The uric acid builds up in the blood and urine, causing several problems including urate bladder stone formation.   

The other reason for these stones to develop is in dogs with a liver condition called a porto-systemic shunt, which also leads to a build-up of uric acid due to impaired liver function.  

The much rarer types of bladder stone include: 

Cystine stones 

Cystine stones are rare and usually the result of a condition called cystinuria. This is a hereditary defect that causes the kidneys to excrete high levels of cystine (a protein ‘building block’) into the urine. Cystine stones seem to be more common in male dogs and can be hard to prevent in dogs that are prone to them, making them difficult to manage long-term.  

Silica stones 

Silica stones are also very rare and are typically seen in dogs that eat large amounts of certain plant proteins or those who drink from natural water sources rich in silica.  

Xanthine stones  

Xanthine stones are most commonly seen in dogs undergoing medical treatment with allopurinol for urate stones, but they can occasionally occur with no known cause.   

How are bladder stones diagnosed? 

This is usually done in a step-wise approach in dogs who are showing clinical signs such as blood in their urine or pain on urination. Because they don’t always cause outward symptoms, sometimes bladder stones are found incidentally – maybe after being seen on an x-ray which is being taken for another reason. While stones usually form in the bladder, they can form anywhere along the urinary tract – in the kidneys, ureters, bladder or urethra – so the whole tract should be checked.  

Initially, a urine sample will be needed to check for blood and infection, then a blood test to check general health / kidney / liver function may be needed too.  

For a firm diagnosis, imaging such as x-rays and ultrasound scans of the bladder are needed. Interestingly, some types of stone do not show up on x-rays, so the absence of bladder stones on an x-ray does not mean they are not there, and your vet may recommend an ultrasound in addition.  

If bladder stones are found with imaging, it is impossible to tell what type they are just by looking. Your vet may have a suspicion of a certain type of stone based on your dog’s age, diet, breed etc, and may recommend treatment based on this alone.  

Sometimes surgery is required as part of the diagnostic process – to collect the stones and get them sent off to an external lab who can tell us what type they are. Ongoing treatment will then depend on this typing.  

How are bladder stones treated? 

The treatment for bladder stones depends on the size, number and type of stone present. Sometimes stones can be ‘mixed’ (a combination of two or more types), which makes the picture a little more complex!  

There are several options: 

Surgery  

Surgery under a general anaesthetic is sometimes needed to remove bladder stones. If your dog has only a few small stones this may be done endoscopically with a little camera and forceps being passed up through the urethra. However more commonly, with larger or many stones, your vet may recommend open surgery called a cystotomy. This involves opening your dog’s abdomen and bladder to directly remove the stones and flush the bladder.  

Urohydropulsion  

In some very specific cases, this technique can be used to avoid full surgery. A urinary catheter is placed, and the bladder is filled and drained repeatedly with saline to flush the stones out of the bladder. This is only appropriate for small stones that will fit easily through a catheter.  

Diet  

Amazingly, some types of stones (e.g. struvite and urate) can be dissolved inside the bladder by feeding your dog a very specific prescription veterinary diet. These diets are cleverly formulated to reduce the pH (in the case of struvite stones) or restrict purines (for urate stones) which allows them to dissolve over several weeks to months. This is a great option to avoid surgery. In dogs that are prone to these stones, continuing to feed these diets long-term can also prevent their recurrence.  

Unfortunately, calcium oxalate stones cannot easily be dissolved with diet so generally require surgical removal. Regardless of the type of stone, if your dog has serious symptoms such as severe bladder inflammation and pain, or if a stone has blocked the urethra, then surgical intervention may still be needed to remove the stones more quickly.  

Treat the underlying cause: 

Control infection 

A urine sample will often need to be sent off to an external lab to see exactly what bacteria are growing and what antibiotics they are sensitive too (called a ‘culture and sensitivity’ test). Then, your dog can be prescribed an antibiotic to clear the infection. Ongoing samples may be needed to monitor for recurrence of infection.  

Medication  

For Dalmations specifically, a medication called allopurinol can be to help dissolve urate stones and prevent their recurrence ongoing too.  

Hydration 

Keeping your dog hydrated will stop their urine becoming too concentrated and keep everything nicely flushed through. This may be done by feeding a canned food (high in water compared to dry kibble), adding water to their meals, using a doggy water fountain, and being especially careful in warm weather to keep their water intake up.  

Ongoing management 

Even after bladder stones are removed or dissolved, dogs may be prone to developing them again. Preventive strategies are likely to be needed ongoing such as feeding a prescription diet, increasing water intake, and catching regular urine samples to monitor for hydration and infection.  

So how common really are bladder stones in dogs? 

The incidence of bladder stones is estimated that 0.3 – 2.8% of all dogs. Of these, about 50% will have struvite stones, 30% will have calcium oxalate stones, 8% will have urate stones, and 1% will have cystine stones. 

Final thoughts 

Bladder stones in dogs are a relatively common but manageable condition. With early detection, proper treatment and preventive care, most dogs can recover fully and live healthy lives. As a dog owner, it’s important to be aware of the signs of urinary discomfort and to consult your vet if you notice anything unusual. Providing your dog with plenty of fresh water, a balanced diet, and regular check-ups can go a long way in preventing bladder stones and keeping your furry friend comfortable and healthy.