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.
OverviewIn 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 IdentificationSigns 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.
TreatmentSurgery 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.
PreventionThough 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.
This article was reviewed by a Veterinarian.