Constantly trying to urinate, straining and passing blood in urine? Is it an infection or does my dog have stones? It could be both! Let me explain why.
Bladder stones (or uroliths) are mineral formations that precipitate in the bladder in certain conditions, such as altered pH, increased urine concentration or high dietary calcium, to name a few.
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Did you know there are different types of bladder stones?
There are certain conditions that must be met for uroliths to form, and different stones need different conditions to precipitate. Here are some of the most common types;
- Struvite: Struvite are the most common type of bladder stones in dogs. They often develop in the presence of a urinary tract infection, because bacteria increase urinary pH (and these stones need a high, or alkaline, pH to form) and produce ammonia, which is a component of struvite.
- Calcium oxalate: Calcium oxalate stones are the second most common type of bladder stones in dogs. Contrary to struvite, calcium oxalate stones need a low (acidic) pH to precipitate. Other predisposing factors include high dietary calcium, genetic predisposition and other medical conditions that increase the amount of calcium excreted in urine.
- Urate: urate stones form due to a deficient metabolism of substances called purines. This can be genetic or secondary to liver disease; urinary tract infections and excess of dietary protein may be the cause in some dogs.
- Cystine: cystine precipitates in acidic urine (low pH), in dogs genetically predisposed (Dachshund, Basset Hound, Chihuahua, English Bulldog, Yorkshire Terrier, Rottweiler, Mastiff, Irish Terrier).
- Silicates: the factors responsible for precipitation of silicate stones are unknown. But their formation is thought to be related to dietary ingestion of silica and silicate – e.g. in some plant materials, or maybe contaminants in food.
What should I look for?
The presence of stones and/or bacteria in the bladder damages the bladder wall, leading to inflammation, thickening and sometimes bleeding of the bladder wall. Therefore, signs to look for include urinating little and often (pollakiuria), straining to urinate (stranguria), the presence of blood in urine (haematuria), or assuming a rigid and hunched posture from pain.
In some occasions, small bladder stones may pass into the urethra (the canal that connects the bladder to the penis (in male dogs) or vulva (in female dogs) and cause a complete obstruction. This situation is an emergency not only because toxins that should be eliminated via urine and stay in the body for too long may cause severe damage to the kidneys and other organs, but also because an overly distended bladder can rupture!
Can I leave bladder stones where they are?
The short answer for this question is no. This is for two main reasons: the presence of stones in the bladder damages it’s inner layer, creating inflammation, pain and predisposing dogs for bacterial infections (when they don’t have it already). Furthermore, when stones are present in the bladder, there is a risk of complete urinary obstruction (a “blocked bladder”). This is an emergency and can be life-threatening.
My dog has bladder stones, what now?
If you detect any of the symptoms above, and you think bladder stones may be the culprits, take your dog to the vets and they can make an investigation plan for you.
This usually starts with a urine sample. Urine analysis is a non-invasive, inexpensive diagnostic tool which provides information on urine pH and the presence of blood, inflammatory cells or bacteria. Sometimes, small crystals can be identified in a urine sample and give a clue on the type of stones that may be present in the bladder, however this is not always accurate and further tests may be needed.
Imaging techniques such as abdominal ultrasound or radiographs are useful tools and often reliable for the diagnosis of bladder stones. They can be used alone or in combination and can provide information on the size and number of stones present.
How can it be treated?
Regarding treatment, bladder stones usually need to be removed surgically. This can be done the traditional way (with an abdominal incision), with minimal invasive surgery or, if the stones are small enough, via cystoscopy (a small camera and instrumentation inserted through the urethra up to the bladder). There are also more recent techniques that use high ultrasonic waves to dissolve the stones into small fragments that can be flushed out of the bladder. However, this has limited availability and is only offered in some referral centres.
Some stones may be treatable using specialised diets to help dissolve them. However, this is risky if the stones are large enough to block the urethra.
After removing and identifying the type of stones present in your dog’s bladder, the causing factors will need to be addressed to prevent recurrence. Of course, different stones form in different circumstances, and the medical treatment will depend on these.
Diet modification is almost always part of the plan, and there are different veterinary diets available to treat the different types of stones; they not only limit the amount of protein, calcium or silicates ingestion but are also formulated to change the urine’s pH. In some cases, medication to alter the pH of the urine may be warranted if diet alone is not enough. Treating existing urinary tract infections is vital in preventing new stone formation.
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