Struvite bladder stones can pose several challenges for our furry friends, along with their owners, who may not be familiar with them. These stones, a common type, form under specific circumstances and are often the result of bladder infection by particular bacteria. Staphylococci and Proteus bacteria are the usual culprits, gaining access to the bladder by creeping up from the lower urinary tract.
Understanding the Statistics
Struvite bladder stones tend to affect females, constituting around 85% of patients. Certain breeds, such as Miniature Schnauzers, Shih Tzus, Yorkshire Terriers, Labrador Retrievers, and Dachshunds, are thought to have an increased risk of developing these stones. The average age of patients with struvite bladder stones is approximately 2.9 years.
Recognizing the Clues: When to Suspect Struvite Stones
While some patients may show no symptoms and the stones are discovered incidentally, there are certain signs that may prompt further investigation. Keep an eye out for bloody urine, recurrent bladder infections (especially with the same organism, particularly Staphylococci or Proteus), or straining to urinate, as these may raise suspicion. Luckily, struvite stones are radio-opaque, meaning they show up readily on radiographs.
The Intriguing Formation of Struvite Stones
Struvite crystals, composed of magnesium, ammonium, and phosphate, are not uncommon in normal urine and don't necessarily require treatment. However, when combined with specific bacteria, such as Staphylococci and Proteus species, a stone is formed. This is made possible by an enzyme called urease produced by these bacteria, which converts urea back into ammonium. The combination of infection and inflammation caused by the ammonium creates a matrix that traps the struvite crystals, resulting in the formation of an actual stone. This process occurs in alkaline urine, making it a telltale sign of struvite stones. The general rule is: no infection, no struvite stones in dogs.
Treatment Strategies: A Diverse Array of Options
1. Dietary Dissolution: The Preferred Approach
Dietary dissolution is the least invasive and often the best treatment option for struvite bladder stones. Several therapeutic diets are designed to dissolve these stones in the bladder by creating urine conditions that are incompatible with the solid state of struvite. It's essential to feed only the prescribed diet until the stone is dissolved, and antibiotics are needed while the stones are still present in the bladder. Radiographs are taken every 4 to 6 weeks to evaluate stone size, and if it shrinks by at least 20 percent, the process continues. Urinalysis is also checked to ensure the right urinary conditions are being created by the diet.
The average duration for stone dissolution is 2 to 3 months, and the diet should be continued for an additional month after stones are no longer visible on radiographs, as smaller stones may not be immediately detectable. Once dissolved, periodic urine cultures are performed to check for infection recurrence. However, be cautious, as there is a risk of urinary tract obstruction as the stone gets smaller and gets lodged in the urethra, particularly in male dogs. For those at higher risk, a faster treatment option may be considered, such as surgery, lithotripsy, cystoscopy, or voiding urohydropropulsion.
2. Surgical Removal: A Direct Approach
Surgical removal is the most direct method, and while it comes with some inherent risks, complications associated with cystotomy (opening of the urinary bladder) are usually rare. The patient typically stays in the hospital for a day or two to ensure normal urine production and assess pain.
3. Voiding Urohydropropulsion: Encouraging Stone Passage
If the stones are small enough, the bladder can be manipulated to promote their expulsion through the urethra using a technique called voiding urohydropropulsion. It involves filling the bladder, agitating it to allow the stones to float freely in the urine, and generating a high-pressure urine stream to force the stones out. Sedation or general anesthesia is needed, and this approach is most effective for small stones and relatively smaller patients.
4. Cystoscopic Retrieval/Laser Lithotripsy: A Minimally Invasive Option
For those seeking to avoid surgery, cystoscopic retrieval or laser lithotripsy may be considered for small stones. This requires specialized equipment usually available at specialty practices.
Preventing a Reappearance: Vigilant Monitoring
After the stones are removed, the focus shifts to prevention. Some animals may be predisposed to bladder infections, which also puts them at risk for recurring struvite bladder stones. Thus, regular monitoring, radiographs, and urine testing are recommended. In cases of recurrent bladder infections, or if stones form as quickly as two weeks after infection, more frequent follow-ups are essential.
Stay Inquisitive and Informed
As caring pet parents, staying vigilant and well-informed is the key to overcoming the conundrum of struvite bladder stones. With expert veterinary guidance, tailored treatment, and preventive measures, we can conquer this puzzling condition and ensure our beloved companions live healthy and joyful lives, free from the grasp of these enigmatic stones.
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