Bladder Stones (Urolithiasis)
Any dog or cat can experience bladder stones caused by a buildup of minerals in the urinary tract. Some dog breeds, however, such as the Dalmatian, and Newfoundland, have a genetic predisposition to developing stones in the urinary tract.
The stones may cause inflammation, bloody urine, frequent urination, painful urination, and straining when the pet tries to urinate. Treatment varies from dietary changes and supplements to surgery, depending on the type and location of the stone.
In some dogs and cats, crystals can form in the urine, causing irritation, infection, pain, and/or obstruction anywhere along the urinary tract (from the kidneys to the tip of the urethra). The crystals can coalesce into stones called urinary calculi or uroliths, hence the name of the resulting disease: urolithiasis.
Because many of these stones in dogs and cats are found in their bladders, veterinarians tend to refer to the uroliths simply as “bladder stones.” However, these stones can lodge in all sorts of uncomfortable places along the entirety of our pets’ urinary tracts. In both dogs and cats, these uroliths most commonly cause problems when they dwell in the bladder, causing irritation, inflammation, or infection, and/or when they pass through the urethra, where they can cause all of the above problems as well as complete urinary obstruction.
Complete obstruction of urine flow is an immediately life-threatening problem, as without the normal elimination of urine, toxins build in the bloodstream. If the flow of urine is not reestablished quickly (within hours), accumulation of these toxins leads to deadly heart rhythms and other potentially irreversible toxic changes to the body that are ascribed to acute kidney failure.
Any dog or cat can experience urinary stones, but there are some types of urolithiasis conditions that happen more often in certain breeds of dogs. These occur when normal metabolic pathways are disrupted, causing excessive excretion of certain stone-forming substances.
In the case of Dalmatians, an abnormality in metabolism leads to an increase of uric acid in the urine. Because uric acid is not very water soluble, it can form urate crystals, which may then coalesce into stones. For other breeds, a defect of another pathway leads to excess quantities of the amino acid cystine. Cystine may also crystalize in the urine and lead to stone formation within the urinary tract. This latter version of urolithiasis is termed cystinuria.
Struvite (aka, triple-phosphate) uroliths and calcium oxalate uroliths are commonly found in many breeds of dogs and cats.
Symptoms and Identification
Signs of urolithiasis are often related to inflammation or infection in the bladder, which is where stones most often accumulate. Bloody urine, frequent urination, painful urination, and straining are common signs.
For dogs and cats whose stones pass into the urethra, urinary obstruction becomes a distinct possibility. In cases where urine flow is completely obstructed, most symptoms are related to the resulting acute kidney failure. Sudden onset of vomiting, anorexia, and lethargy is most typical of these cases. Due to the small aperture of the penile urethra, males experience complete obstruction more often than females.
Diagnosis is usually achieved with X-rays or ultrasound. Alternatively, contrast urography (with air or dye) is another possible way to demonstrate the presence of stones that don’t show up on normal X-rays (as is often the case of urate uroliths). Urinalysis and urine culture and sensitivity are critical parts of this process. Definitive diagnosis, however, can be achieved only after stones are retrieved and analyzed for their chemical makeup.
- For urate uroliths, Dalmatians are the quintessential breed, but English bulldogs may also be predisposed.
- In the case of cystinuria, a wide variety of breeds can be affected, inclusing English bulldogs, dachshunds and Newfoundlands.
- For struvite (triple-phosphate) and calcium oxalate are common stones in dogs and cats, and are found in a wide range of breeds.
- Xanthine uroliths are seen in Cavalier King Charles spaniels.
Surgery is almost always required for uroliths that cause obstruction. A cystotomy is the most common urolith surgery, and requires an incision in the abdomen and urinary bladder for stone removal. When urethral obstruction occurs, however, surgeons may perform a urethrotomy (surgically entering the urethra) to retrieve the stones and reestablish normal urine flow.
Another possibility for pet owners with access to highly specialized facilities includes the use of lasers and sound wave technology to break down stones so that they might pass.
For some types of uroliths and crystals, there are nonsurgical therapies. Diet changes, nutritional supplements, and drugs can sometimes be implemented to dissolve stones, particularly in cases of struvite and urate uroliths.
In many cases, treating secondary urinary tract infections with antibiotics may be part of the treatment protocol.
Though the genetic traits that allows for certain kinds of stone formation are preventable only through judicious breeding, stone formation can often be prevented –– though not always –– through diet and nutritional supplements once at-risk individuals have been identified.
Canine Bladder Infections
A bladder infection occurs when microbes (usually bacteria) get into the bladder and proliferate. Any dog can get a bladder infection, though females are more likely to get one. Because the disease irritates the organ, it increases the pet’s urge to urinate. Frequent squatting or straining without a lot of results is the biggest sign a pet has a bladder infection. Urine might also be cloudy or tinged with blood. Bladder infections can even lead to bladder stones (and vice versa). Treatment for the infection includes a course of antibiotics. If stones occur they must be removed through surgery, broken up by sounds waves, or eliminated via a special diet.
The bladder is an expandable sac, like a balloon, that lies toward the back of the abdomen. Urine flows from the kidneys, through the tube-shaped ureters, and into the bladder, where it is stored before being eliminated from the body through a tube called the urethra.
Urine in the bladder is normally sterile unless bacteria travel up the urethra and cause an infection. Bacteria may be introduced from the nearby rectal area or from the genital tract. Conditions such as diabetes can increase the risk of developing bladder infections, as can medications that depress the immune system, including high-dose or long-term corticosteroids.
In long-standing infections, the bladder tissue can thicken and scar, creating more places for bacteria to grow. Long-term infection also increases the chances that infection will spread upstream to the kidneys or cause bladder stones to form.
Symptoms and Identification
Urinary infections irritate the walls of the bladder, so pets with bladder infections have the urge to go even when there is little urine present. They will frequently pass small amounts of urine, often tinged with blood. Constant squatting and straining without passing much urine, or having urinary accidents in the house are typical indicators of potential urinary tract infection.
Bladder infections change the chemical makeup of the urine, which makes it easier for minerals in the urine to crystallize and form stones. Bladder stones add to the irritation and create places for bacteria to hide from bodily defenses and antibiotics.
On some occasions, bladder stones can also block the outflow of urine, which is a serious emergency situation. Pets with urinary obstruction can have a swollen, painful abdomen and strain repeatedly without passing urine. This is a medical emergency!
Your veterinarian can usually diagnose an uncomplicated bladder infection based on your pet’s history and a urinalysis. In some cases, a urine sample might be sent to a laboratory to determine the specific bacteria involved (through a culture and sensitivity test) as well as an effective antibiotic for treatment. Abdominal X-rays or ultrasound imaging are sometimes needed to look for stones, tumors, or other abnormalities involving the bladder.
Treatment for a simple bladder infection usually consists of a week or two of antibiotics. Chronic or severe infections may require longer treatment. Infections that clear up and then recur may suggest an underlying problem requiring additional diagnostic testing and treatment.
If bladder stones are present, there are several options for eliminating them:
- A veterinarian can perform surgery to open the bladder and remove the stones.
- A veterinarian can use a sterile probe routed up the urethra to crush the stones using sound waves and then flush out the pulverized crystals. This is a specialized procedure that may require referral to a specialty practice.
- You can feed your pet a specialized, prescription diet that changes the chemical makeup of the urine and causes the stones dissolve. This is the least invasive technique but takes more time and commitment and is not effective for all bladder stones.
- Specialized, prescription diets are also used to help prevent recurrence in pets prone to bladder stone formation.