Bladder Stones in Dogs

Bladder stones are a common urinary system problem for many pets including cats, guinea pigs, and dogs. These rock-like clumps of minerals can cause bladder issues such as pain, inflammation, bleeding, infection, trouble urinating, and in severe cases, a complete inability to urinate, which is a life-threatening emergency. So, while bladder stones may be common, they are also potentially serious if left untreated.

While any dog can develop bladder stones, certain breeds are more predisposed to this painful condition, including dachshunds, miniature schnauzers, Labrador retrievers, and Yorkshire terriers. Some types of bladder stones more commonly afflict male dogs, while others are likelier to strike female dogs. And most dogs with bladder stones are young adults to seniors, not puppies.

Preventative measures can sometimes be taken for dogs prone to developing recurrent stones, and various treatment options exist for dogs diagnosed with bladder stones, depending on the type of stone that has formed. By learning more about bladder stones, dog owners may be able to help prevent them from forming, know how to recognize the signs and symptoms in their dog if they do, and understand the treatment options that are available to them.

What Are Bladder Stones?

Bladder stones, technically referred to as calculi or uroliths, are hard, stone-like structures that form within the bladder of a dog. These stones can be made up of various minerals, form a variety of shapes, and may be associated with bacterial infection. A dog can have one or many bladder stones, and they can grow to be very large or stay very tiny, although it is most common for there to be several stones in different sizes within the afflicted dog's bladder. Although both are urinary system disorders, bladder stones are different from kidney stones since they form inside the bladder and not the kidney of a dog.

There are several different types of bladder stones that dogs can develop.

• Struvite stones: Struvites are also referred to as triple phosphate or magnesium phosphate stones. Dissolved struvite is a normal part of a dog's urine but when changes in the urine occur (often as a result of bacterial infection), it can lead to the creation of stones. These stones are the most commonly seen type in dogs, particularly female dogs. They most often develop in dogs between two and four years of age.
• Calcium oxalate stones: Almost as common as struvites, calcium oxalates are bladder stones that are linked to overly acidic urine, although their formation is poorly understood. They most commonly affect male dogs between the ages of five to 12.
• Urate stones: Urate stones are not very common but are seen in certain populations of dogs. For example, dalmatians are genetically predisposed to developing urate stones. These stones most often strike male dogs.
• Cystine stones: One of the more rare types of bladder stones, cystine stones are almost exclusively seen in male dogs. The tendency to develop them is an inherited characteristic.
• Silica stones: These rare bladder stones may be linked to dietary factors, including an excess of corn and soy.

Symptoms of Bladder Stones in Dogs

Very tiny stones, which can be as small as a grain of sand, sometimes pass without symptoms, especially in female dogs. However, most dogs will experience symptoms with this condition, including straining to urinate and blood in the urine (hematuria).

When a dog has a urinary issue, it will often exhibit signs and symptoms of discomfort and trouble urinating. Licking at the urinary tract opening is an indication that something might be uncomfortable or painful in that region, and straining or crying while urinating may also be seen in dogs with bladder stones. Frequent urination, with only small amounts of urine coming out, is yet another symptom.

Some dogs might urinate in inappropriate spots, such as inside the house, due to the urgency and pain of the bladder stones. Even if their bladders aren't full, dogs may feel like they need to urinate. In rare cases, dogs may become completely unable to urinate due to a stone blocking the urethra, which is a life-threatening emergency.

Bladder stones irritate and inflame the bladder wall, which is why one of the most obvious signs that a dog has the condition is hematuria, or bloody urine. However, other health problems can cause this symptom as well. You might observe actual blood clots in your dog's urine, or it might appear pink or red.

Causes of Bladder Stones

Veterinarians are not entirely sure of exactly what causes bladder stones in dogs, but the most commonly accepted explanation is the precipitation-crystallization theory. This states that due to a variety of reasons, which can include infection, genetics, diet, or metabolism, the level of certain minerals rises abnormally high in the dog's urine.

When the level of the minerals in the dog's urine becomes too high, or saturated, the urine cannot hold any more of the mineral. It then precipitates, or becomes solid, and forms into crystals. These crystals are sharp and irritate the lining of the bladder, causing it to secrete mucus. The crystals and mucus stick together, gradually forming larger and harder stones.

Depending on the type of stone and the level of urinary tract infection, if any, bladder stones can develop in as little as two weeks, although it generally takes a few months for large stones to grow.

Certain breeds of dogs are much more prone to various types of bladder stones than others. For example, dalmatians, English bulldogs, and individuals with some types of liver disease are more likely to develop urate stones than other dogs. Female dogs of all breeds are more likely than males to develop struvite stones, but males are more likely than females to develop calcium oxalate stones. Dogs with urinary tract infections are more likely to develop struvite stones than dogs without urinary tract infections.

Shih tzus, Yorkies, bichon frises, lhasa apsos, and miniature schnauzers are at risk for developing struvite or calcium oxalate stones, and German shepherds and Old English Sheepdogs (among other breeds) are more likely to develop silica stones than other dogs. Dogs who have family members that have developed cystine stones are more likely than others to develop cystine stones themselves.

A dog that has a history of bladder stones could be considered at high risk for reccurrence depending on breed and diet.

Diagnosing Bladder Stones in Dogs

X-rays are the most commonly utilized diagnostic tool that veterinarians use to confirm a dog has bladder stones. Since bladder stones are mineral-containing items, they usually reflect the X-rays and show up as white objects inside your dog's bladder. A small percentage of bladder stones, however, such as urate stones or any stone that is tiny, do not reflect X-rays well and show up best on an ultrasound.

Your veterinarian may also suspect that your dog has or is at risk for stones based on the presence of crystals (struvite or calcium oxalate, for example) in a fresh sample of urine. These crystals may be seen when urine is looked at under a microscope during a urinalysis.

Treatment & Prevention

There are four basic treatment options for bladder stones: special diet, surgery, using ultrasound or lasers to break the stones apart, and flushing them out with a saline solution. Your veterinarian will recommend the best choice for your dog based on the type and size of the bladder stones.

A special diet that is formulated to dissolve stones works for some dogs with struvite stones. This is a non-invasive treatment and so is especially good for dogs that might not be able to tolerate anesthesia. However, some dogs refuse to eat the special food, it takes weeks to months for the stones to dissolve, during which time your dog is still at risk of urinary obstruction, and dietary dissolution of stones doesn't always work.

Surgery to remove the stones is the most commonly used treatment for bladder stones that cannot be dissolved or in emergency cases where a stone has blocked the urethra and the dog is not able to urinate. The procedure is called a cystotomy. The veterinarian will surgically open the dog's bladder and remove the stones. Most dogs do very well and recover rapidly after a cystotomy. However, there are always risks with anesthesia, especially if the dog is elderly or in generally poor health.

The use of lasers or high-frequency ultrasound to break up stones into fragments small enough to then flush out of the bladder is another option for some dogs. This is a fairly quick and well-tolerated procedure for most canine patients, but can be expensive, and not all veterinarians have the equipment to perform it.

Urohydropropulsion is a procedure generally performed under general anesthesia in which a catheter is placed into the dog's bladder, and then liquid is pumped into the bladder to flush the stones out. This is typically only an option if the stones are small.

Generally, bladder stones are difficult to predict and prevent. However, once a dog has had bladder stones, it is at higher risk for developing them again in the future. Because of this, your vet might recommend that your dog remain on a special diet that helps prevent a recurrence of stones.

Prognosis for Dogs With Bladder Stones

Most dogs with bladder stones will recover with treatment. However, it is fairly common for these stones to reoccur, especially in breeds that are more highly susceptible to stone formation. Because of that, your vet may recommend that your dog remain on a special diet for the rest of its life and have regular urinalysis tests to check for signs of stones or urinary tract infection.