When we talk about “bladder stones” in dogs, we’re actually referring to urinary calculi, a condition known as urolithiasis. These stones can form anywhere along the urinary tract, from the kidneys to the urethra. Interestingly, in dogs, a staggering 85% of these stones are found within the bladder.
Signs and Diagnosis
Dogs with bladder stones might exhibit blood in their urine, frequent urination, and straining during urination. They may also lick their genital area excessively. Some dogs show no signs until a routine physical examination reveals the presence of stones, often through abdominal palpation or x-rays. X-rays can identify radiopaque stones as white circles, while radiolucent stones require a special dye to be outlined in the x-ray film.
Formation of Bladder Stones
Bladder stones begin as microscopic crystals in the urine, which over time, aggregate into sand-like grains. These grains serve as a foundation for further precipitation, eventually forming stones that can grow quite large.
Types of Bladder Stones
Bladder stones in dogs are categorized by their chemical composition, including struvite (magnesium ammonium phosphate), calcium oxalate, calcium phosphate, cystine, and ammonium urate, among others. Each type has unique characteristics regarding breed susceptibility and factors influencing their formation.
Causes of Bladder Stones
The development of bladder stones is influenced by several factors, including:
- Genetics: Some dogs are genetically predisposed to produce higher levels of stone precursor substances in their bodies.
- Concentration of Stone Constituents: Diet, water intake, and metabolism can affect the concentration of these substances in the urine.
- Urine pH: The acidity or alkalinity of urine plays a role in whether constituents form stones. Diet significantly influences urine pH.
- Bacterial Infections: Infections, particularly those producing urease, can lead to struvite crystal formation and increase urine alkalinity.
Bacterial metabolism by-products can also enhance crystal formation, leading to stone development if crystals form rapidly and in large quantities.
Treatment Options
Treatment for bladder stones can be medical or surgical, depending on the stone’s size, type, and location. Surgical removal, known as cystotomy, involves opening the bladder to extract the stones. Urohydropropulsion is another method used for small stones, where sterile saline flushes the stones out through a catheter. Medical management, particularly for struvite and ammonium urate stones, involves dietary changes, increased water consumption, and controlling urinary tract infections.
Diet and Prevention
Specialty diets can dissolve certain types of stones and are crucial for preventing their recurrence. For example, Hill’s s/d diet can help dissolve struvite stones by making urine more acidic and reducing the formation of precursor substances. It’s important to note that these diets should not be used indefinitely and are not suitable for dogs with heart failure or kidney disease. After the initial treatment, a maintenance diet is recommended.
Increasing water consumption is also vital, as it helps flush out crystals and prevent stone formation. This can be achieved by feeding canned diets, adding water to dry food, or using flavored broths.
Summary
Bladder stones can affect any part of a dog’s urinary tract. Treatment involves either physical removal or dissolution through special diets. Preventive measures include feeding special diets, increasing water intake, and managing urinary pH. Controlling urinary tract infections is particularly important for preventing struvite stone recurrence.