Urinary crystals in dogs form due to an abnormal pH and usually due to an infection. Unlike cats, dogs rarely form struvite crystals from urinary excretion of dietary minerals alone. Consequently, testing and treating for urinary crystals in dogs should include screening for a urinary tract infection.
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Rule Out Infection
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Bacteria under a microscope Testing for urinary crystals in dogs must also include screening for an infection. According to DVM News Magazine, less than two percent of dogs with urinary crystals occur due to dietary mineral excretion in sterile conditions. In contrast, more than 95 percent of cats form crystals due to dietary mineral excretion in sterile conditions. Since crystal formation is more common in cats, the likelihood of an infection in dogs is often forgotten. In dogs, struvite forms from magnesium ammonium phosphate (MAP) under alkaline conditions usually due to urease producing microbes (usually staphylococci). A microscopic exam and bacterial culture should be performed to identify infection.
Urinalysis
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Microscopes will help identify sediment in urine Ruling out an infection is usually part of a comprehensive urinalysis. However if you are only looking for crystals an infection may be missed. Testing the pH of urine will determine whether or not it is alkaline enough for crystal formation. In very rare cases, extreme numbers of crystals precipitating out into the urine may be seen by the naked eye in the urine sample and look as though there is sand in the urine. Preferably, urine is placed on a glass slide and examined under a microscope at 40x power to identify crystals.
Treatment
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Treatment consists of dietary modification and antimicrobial medications. A prescription diet formulated to dissolve urinary crystals will be extremely helpful in lowering the amount of dietary minerals that contribute to crystal formation. However, as stated above, dogs usually form crystals due to an infection so changing the diet will not cure a dog of urinary crystals. Identifying the offending bacteria by growing it on a culture medium will also enable you to do a sensitivity test to determine which antibiotics the bacterium is most susceptible to. Once the most effective antibiotic is determined, immediately begin treating the infection as it is the underlying cause of crystal formation.
Complications
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Often times urinary crystals can form uroliths, aka stones. Struvite uroliths may need to be removed surgically. To avoid this complication, begin treatment right away because the longer the crystals remain in the bladder, the more likely they are to begin clumping together to form stones. The only way to determine whether or not stones formed is to take a radiograph of the bladder.
According to DVM News, microbes are often caught inside the crystals during formation. So while the infection may be gone within the bladder mucosa, as crystals continue to dissolve, more microbes may be released and reinfect the bladder. Because of this complication, antibiotic therapy may need to be extended.
Prognosis
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The prognosis for urinary crystals in dogs is very good to excellent as long as the underlying cause is treated. Infection must be identified and treated to ensure a positive prognosis in treating the crystals.
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