Bladder stones are a common issue that can affect both dogs and cats, causing discomfort and other symptoms such as blood in the urine or chronic bladder infections. Understanding what bladder stones in dogs and cats are, the different types, how they form, and the best ways to treat and prevent them can help you manage this condition.
What are bladder stones in dogs and cats?
Bladder stones are exactly what they sound like – hard, stone-like formations that develop in your pet's urinary bladder. Sometimes, there's just one lonely stone, but other times, there can be a whole bunch, ranging in size from tiny grains of sand to very large pebbles.
What are the clinical signs of bladder stones?
Bladder stones can be sneaky, especially in the early stages. Cats and dogs with bladder stones might not show any obvious signs at all (asymptomatic), while others may reveal a range of symptoms.
Here are some common signs of bladder stones to watch out for:
- Blood in the urine (hematuria)
- Frequent urination (pollakiuria)
- Straining to urinate
- Licking the genital area
What are the different types of bladder stones in dogs and cats?
Bladder stones aren't all created equal. Just like rocks, they come in different types, each with its own unique composition and causes.
Although bladder stones come in different types, the most common ones we see in our patients are struvite stones and calcium oxalate stones.
Struvite stones
These stones are one of the most common types of bladder stones in dogs, particularly in female dogs. They're primarily made up of magnesium, ammonium, and phosphate, hence their other name, triple phosphate stones.
Struvite bladder stones often form in response to a urinary tract infection, as certain bacteria can change the pH of your dog's urine, making it more alkaline and promoting struvite crystal formation.
Although urinary tract infections are the most common cause of struvite bladder stones in dogs, anything that will raise the pH of the urine and make it more alkaline, can cause these stones.
This is much different from struvite stones in cats. Almost all cases of struvite bladder stones in cats are NOT due to urinary tract infections, but rather diet and genetic influences. It is not unusual for cats to have crystals in their urine with struvite stones.
Calcium oxalate stones
These are the second most common type of bladder stone in dogs and the most common in cats.
Calcium oxalate stones are made up of, you guessed it, calcium oxalate! Unlike struvite stones, they tend to form in acidic urine with a low pH.
Dietary factors, breed predisposition, and certain medical conditions such as elevated blood calcium levels (hypercalcemia) can all contribute to the formation of calcium oxalate stones.
Calcium oxalate bladder stones typically have sharp, jagged edges making them very uncomfortable and often cause bloody urine due to their abrasive nature.
Other stone types
While less common, there are a few other types of bladder stones that can occur in both dogs and cats. These include:
Urate stones: These are often seen in Dalmatians and certain other breeds. Urate stones are also associated with liver diseases such as portosystemic shunts.
Cystine stones: These are rarer and usually related to a genetic defect and affect both dogs and cats.
Silica stones: These are also quite rare and are related to increased dietary intake of silica.
Knowing the type of stone your pet has is extremely important, as it helps your vet determine the best course of treatment and prevention.
Why do bladder stones form in dogs and cats?
As we've seen, bladder stones come in a few different varieties, and each type has its own unique set of risk factors. Let's break it down a bit further:
Causes of struvite stones in dogs and cats
The formation of struvite stones is often linked to uncomplicated bladder infection or cystitis, especially in dogs.
Certain bacteria produce an enzyme called urease, which increases the pH of the urine, making it more alkaline. This alkaline environment is perfect for struvite crystals to form and clump together, eventually hardening into stones.
However, it's important to note that cats commonly form struvite bladder stones even without a urinary tract infection. The most common cause of struvite stones in cats is dietary.
Causes of calcium oxalate stones in dogs and cats
The story behind calcium oxalate stones is a bit different. Their formation is less likely to be associated with infection and more related to other factors, such as:
- Diet: Certain diets with low protein and high carbohydrates can increase the risk of calcium oxalate stone formations.
- Genetics: Some breeds, like Miniature Schnauzers, Lhasa Apsos, and Yorkshire Terriers, are predisposed to developing these stones.
- Medical conditions: Certain medical conditions, like Cushing's disease or hypercalcemia (high calcium levels in the blood), can also increase the risk. Obesity is also a risk factor for the development of calcium oxalate stones.
Other contributing factors
Regardless of the type of stone, there are a few general factors that can contribute to their formation in both dogs and cats:
- Urine concentration: If your pet's urine is highly concentrated (meaning it has a high mineral content), it's more likely that crystals will form.
- Urine pH: The acidity or alkalinity of the urine can influence which type of stone is more likely to form.
- Urinary stasis: When urine sits in the bladder for too long (due to infrequent urination), or if it is too concentrated, it gives minerals more time to crystallize.
Remember, these are just some of the most common causes of bladder stones. Each pet is unique, and your veterinarian will be able to determine the specific factors contributing to your particular pet's stone formation.
How fast can bladder stones form?
You might be wondering how quickly bladder stones can develop in your pet's bladder. The answer isn't always straightforward, as it can vary depending on the type of stone and individual factors.
Struvite stones, for example, are notorious for their rapid formation. In some cases, they can develop within a matter of weeks, particularly if your pet has an uncomplicated bladder infection or cystitis.
On the other hand, calcium oxalate stones tend to form more gradually, often taking months or even years to reach a problematic size.
So, while some stones can seemingly appear overnight, others are a slower burn. However, regardless of the type of stone, you need to remember that early detection is key. The sooner bladder stones are diagnosed, the easier they are to manage and treat.
How are bladder stones diagnosed?
If you suspect your dog or cat might have bladder stones, don't worry! In most cases, diagnosing bladder stones in pets in relatively straightforward.
Here's how bladder stones are diagnosed:
- Physical examination: Sometimes, your vet can actually feel bladder stones during a physical exam by gently palpating (feeling) your pet's abdomen. Please do not attempt to do this on your own!
- X-rays: X-rays are a common way to visualize bladder stones. While not all types of bladder stones show up on X-rays, most, including calcium oxalate and struvite stones, do.
- Urinalysis: A simple urine test can reveal a lot about what's going on in your pet's bladder. It can detect microscopic crystals, blood, and infection, and even provide clues about the type of stone present.
- Ultrasound: An ultrasound can give your vet a more detailed look at the bladder stones, helping to determine their size, number, and location. It can also help rule out other potential causes of your pet's symptoms. It is also good for stones that may not appear on X-rays.
What is the treatment for bladder stones in dogs and cats?
The good news is that there are several effective treatment options available for bladder stones in both dogs and cats. The best approach will depend on a few factors, including the type of stone, the size and number of stones, and your pet's overall health.
Dietary dissolution
In some cases, stones can be dissolved without the need for surgery! Special therapeutic diets are formulated to dissolve the stones by altering the pH of the urine and reducing the concentration of stone-forming minerals.
If your dog has struvite stones because of a urinary tract infection (UTI), treatment of the UTI can regulate the urine pH and this will dissolve struvite stones.
My only concern with this method is that as the stones break down, there is the potential for urethral obstruction where the smaller stone fragments can get lodged in the urethra, causing a blockage.
Minimally invasive procedures
For stones that can't be dissolved with diet alone, minimally invasive procedures may be recommended.
An example would be voiding urohydropropulsion. This technique involves flushing the bladder with sterile saline to flush the stones out through the urethra. It's typically only successful for small stones and requires sedation or anesthesia.
Surgical Removal
In most cases, surgery may be the best option, especially for large stones or those causing a urinary blockage.
The most common surgical procedure is called a cystotomy. During this surgery, your veterinarian will make an incision in the bladder and remove the offending stones.
How can you help prevent bladder stones?
While we can't completely eliminate the risk of bladder stones, there are several things you can do to make them less likely to form:
1. "Dilution is the solution to pollution"
Water is key! Encourage your pet to drink plenty of fresh water throughout the day. This helps to dilute their urine and prevent the minerals from becoming too concentrated, reducing the risk of stones forming.
Consider using a water fountain to entice your pet to drink more, and try adding a little low-sodium broth or water from a tuna can (for cats) to their water bowl.
Perhaps the easiest way of supplementing water is by feeding your dog or cat canned food. You do not need to feed your pet 100% canned food, but since canned food is largely water, it can help increase their overall water intake.
2. An appropriate veterinary diet
We routinely use diets to help prevent bladder stones in dogs and cats. The type of diet is very important and should be determined based on the type of stone you are trying to prevent.
When trying to prevent struvite stones, feeding a diet that has a urinary SO index ensures that it will create a target pH that prevents struvite crystals in dogs, and therefore stones.
Diet change is one of the pillars of preventing calcium oxalate stones in dogs and cats. A diet that is slightly alkalizing and higher in moisture is often beneficial in preventing calcium oxalate stones.
3. Regular urine checks
If your pet is at risk of bladder stones, having their urine tested at least twice a year is a good idea. A urinalysis is a simple test that can be performed to check for any signs of urinary abnormalities, including the presence of crystals or microscopic blood.
In high-risk breeds, such as miniature schnauzers, I recommend having a bladder X-ray performed at least once a year.
In conclusion, bladder stones are a significant health concern for both dogs and cats, causing discomfort and potentially serious health issues. Understanding the different types of stones, such as struvite stones and calcium oxalate stones, and knowing their causes, can help you take preventive measures. Treatment options range from dietary changes to surgical removal, depending on the type of stone and severity. By maintaining a proper veterinary diet and ensuring your pet has an above-normal water intake, you can significantly reduce the risk of stone formation.