Bladder Stones
Both dogs and cats can get bladder stones. There are several common types of bladder stones and different conditions that allow them to form. Breed, age, gender and diet all play a role in the formation of bladder stones. Fortunately, it is rare to get kidney stones in our companion animals. Bladder stones are less painful and easier to treat, and rarely cause kidney damage, but can still be a challenge to manage.
What is the Difference Between Crystals and Stones in the Bladder?
Before a stone forms in the bladder, microscopic crystals are present as a sort of "sludge" in the bladder. Symptoms are seen with crystals in the urine as well as stones themselves. Over time, if the crystals are allowed to remain in the bladder, they will congregate to form stones. The stones can be made up of one type of crystal or of several different types.
Types of Urinary Crystals and Stones
- Magnesium Ammonium Phosphate (Struvite) - These are very common crystals that we see in both dogs and cats. These crystals usually form in alkaline urine. They can form as a result of a urinary tract infection, or can be the underlying cause of recurrent UTIs. Struvite plugs are also the usual cause of urinary blockages in cats. These crystals can usually be dissolved with dietary management. Predisposed breeds include Schnauzers, Shih Tzus, Yorkshire Terriers and Dachshunds, and female dogs are more likely to develop struvite stones.
- Calcium Oxalate - These are the other very common bladder stone we see, primarily in cats. These crystals are very spiky and can cause tremendous discomfort in the bladder. Calcium oxalate crystals develop in acidified urine. These stones usually cannot be dissolved with diet therapy and have to be removed surgically, and then diet is used to hopefully prevent their recurrence. Breed predispositions include Himalayans and Burmese cats. Since there has been a link between calcium oxalate crystals and chronic kidney failure in cats, it is imperative to treat these stones as soon as they are diagnosed.
- Uric Acid - A less common bladder stone, these develop almost exclusively in Dalmations, English Bulldogs, and in dogs with a liver shunt. An ultrasound is needed to confirm a diagnosis because these stones may not show up on an x-ray. These stones may be able to be dissolved with dietary and medical therapy.
- There are other types of crystals that we see rarely on urine samples, and each of them would have a different treatment. Since they are so rare, we will not discuss them here.
Symptoms of Bladder Stones
Most dogs and cats with crystals or stones in the bladder will present with symptoms characteristic of a urinary tract infection, or inappropriate urination. These include:
- Straining to urinate
- Frequent urination in small amounts
- Increased water consumption
- Loss of housebreaking (dogs) or going outside of the litter box (cats)
- Blood in the urine
- Vocalizing when urinating
- Not urinating, painful in the abdomen, hard abdomen, vomiting, depressed (this is a medical emergency and could mean a stone is blocking the passage of urine!)
Diagnosis
The first test we run when we suspect a problem with urination is a urinalysis. This examines the urine to see if there is evidence of an infection or crystals in the urine. Sometimes there can be stones without the microscopic crystals in the urine. This is why we will usually recommend an x-ray or bladder ultrasound to make sure there are no stones in the bladder. A urine culture may also be recommended if your pet has had frequent problems with UTIs.
Treatment: Medical vs. Surgical
Treatment all depends on what type of stone your pet has. With struvite stones, we usually will recommend to place your pet on a strict diet that is designed to dissolve the stones over time. We will take serial x-rays to make sure the diet is working. Your pet will need to stay on the prescription diet for the rest of his or her life in order to prevent the stones from returning. Even on prescription diets there is a chance of recurrence so monitoring your pet for any recurring symptoms is important.
For calcium oxalate stones, medical dissolution with a prescription diet can be tried, but usually is ineffective. After 30 days, if there is no indication of the stone getting smaller, surgery is required to remove the stones. With cats and the high risk for chronic kidney failure combined with the poor chance of dietary treatment working, surgery is usually the better option. A bladder surgery will usually cost around $1000. Once the stones are removed we send them for analysis at a lab to see exactly what type or types of crystals make up the stone. This will help us to determine the right prescription food for your pet.
During the time period we are trying to dissolve your pet's bladder stones, it is important to closely monitor them for any worsening clinical signs of a UTI. Bladder infections are common in pets with bladder stones because the stones serve as a nice island for bacteria to attach to and grow. In addition, though rare, if the stones become small enough to pass through the bladder but are too big to be excreted out the urethra, this could result in a urinary blockage. These pets cannot urinate, their bladders fill and become very painful, and can rupture. This is an emergency situation that more commonly affect cats, especially males. If your pet has not urinated within 12 hours or is acting lethargic, painful, or is vomiting then immediate medical attention is needed!
For calcium oxalate stones, medical dissolution with a prescription diet can be tried, but usually is ineffective. After 30 days, if there is no indication of the stone getting smaller, surgery is required to remove the stones. With cats and the high risk for chronic kidney failure combined with the poor chance of dietary treatment working, surgery is usually the better option. A bladder surgery will usually cost around $1000. Once the stones are removed we send them for analysis at a lab to see exactly what type or types of crystals make up the stone. This will help us to determine the right prescription food for your pet.
During the time period we are trying to dissolve your pet's bladder stones, it is important to closely monitor them for any worsening clinical signs of a UTI. Bladder infections are common in pets with bladder stones because the stones serve as a nice island for bacteria to attach to and grow. In addition, though rare, if the stones become small enough to pass through the bladder but are too big to be excreted out the urethra, this could result in a urinary blockage. These pets cannot urinate, their bladders fill and become very painful, and can rupture. This is an emergency situation that more commonly affect cats, especially males. If your pet has not urinated within 12 hours or is acting lethargic, painful, or is vomiting then immediate medical attention is needed!
Life-long Management
Once your pet develops bladder stones, he or she will be at risk for developing new stones throughout their lives. Prescription diets can help manage the stones and prevent future recurrence, but are not 100% effective in every case, especially with calcium oxalate stones. Checkups at least twice a year to take x-rays to monitor for bladder stones are important to make sure we do not need to alter the maintenance treatment we have your pet on. Luckily, most pets that adhere to their diets do very well and have a great quality of life!