Bladder stones in your pets

Dr. Cat Angle, DVM


Urolithiasis or Bladder Stones

Bladder stones are a common problem in dogs and cats that cause painful, frequent, small urinations. They originate when minerals in the urine become concentrated in the bladder and connect together to form crystals and then stones. Bladder stones are seen more commonly in some breeds of dogs than others and can generally be prevented with early detection, excellent hydration and good dietary choices. For these treatments to work it is important that they have the desired effect on the urine. A Petnostics kit can help you monitor at home and make sure your pet’s prescription diet is getting the job done. The kit can also help if you have adopted a breed known to be high-risk for urinary stones such as a Dalmatian, Shih Tzu, Bichon Frise or Lhasa Apso.

Struvite Stones

The most common bladder stones are in dogs and for cats are struvite stones. Struvite stones are formed of magnesium, ammonium and phosphate. In dogs, struvite stones generally develop when a urinary tract infection is present. The bacteria causing the urinary tract infection increases the pH of the urine allowing these minerals to bind together. Most struvite stones in dogs can be dissolved by treating the underlying infection and lowering the urine pH with an acidifying diet. In cats, more than 95% of struvite stones exist in bladders free of infection. Struvite stones in cats can generally be dissolved with an appropriate diet designed to create dilute urine with low (acidic) pH and low levels of magnesium, ammonium and phosphorus. With appropriate therapy it takes, on average, 2-3 months to dissolve a struvite stone that was caused by a bladder infection and 3-6 weeks to dissolve a sterile struvite stone. Dissolution may not be effective if the antibiotic selected is not fully eradicating the bacteria or if the stone is a mixture of struvite and another type. If dissolution is not an option, the stone can be physically removed using surgery, hydropulsion or lithotripsy.

Ideal urine properties:

  • pH less than 6.8
  • Specific Gravity between 1.010 and 1.020
  • Once the stone is fully dissolved, urine should be free of Red Blood Cells (RBCs)

Calcium Oxalate Stones

Calcium Oxalate is the second most common type of bladder stone. Unlike struvite stones, calcium oxalate stones cannot be dissolved and must be physically removed. Calcium oxalate uroliths most commonly develop in Miniature Schnauzers, Lhasa Apsos, Yorkshire Terriers, Bichons Frises, Shih Tzus, and Miniature Poodles. They occur more commonly in older males who are fed a dry/kibble diet. Pets with elevated blood calcium levels or hyperadrenocorticism are more likely to develop this type of stone. Calcium Oxalate stones are easily viewed on radiographs of the urinary tract. Surgery is generally performed to remove large stones.  Small stones can sometimes be removed by hydropulsion and in some places lithotripsy (break down of the stone within the bladder) can be a treatment option. Once the stone is removed, prevention is critical.  About 50% of pets have recurrence of their stone within 3 years of removal. Prevention requires that the pet be fed a diet with restricted amounts of protein, oxalate and that promotes formation of alkaline (elevated pH) urine.

Ideal urine properties:

  • pH between 6.5 and 7.5
  • Specific Gravity between 1.010 and 1.020
  • Once 1 month post surgical removal, urine should be free of Red Blood Cells

Urate Stones

Urate stones are the third most common type of bladder stones in companion animals and represent 8% of stones in dogs and 4.63% of stones in cats. Urate stones develop in urine that is overly acidic. Dalmations and English Bulldogs are overrepresented when it comes to suffering from urate stones because they have inherited differences in the way they metabolize uric acid. Most Dalmations who develop urate stones are between 1-4 years old. Pets who suffer from hepatic disease and certain breeds (Miniature schnauzers, Yorkshire terriers, and Shih Tzus) are also at increased risk for developing this type of stone. Two-thirds of dogs with this type of stone can have their stone successfully dissolved in 2-3 months after being fed a prescription diet.  In some, treatment with Allopurinol will help.     


Prevention is key

Bladder stones are a common problem in our canine and feline friends that can be challenging to treat. Fortunately, bladder stones are generally preventable. If you have a pet who is a high risk breed, or has been diagnosed previously with a stone, monitoring their urine and promoting conditions that discourage stone formation may help you save your pet and your checking account a lot of discomfort.  

  1. Osborne CA.  “Medical dissolution and prevention of canine uroliths. Seven steps from science to service.”  Vet Clin North Am Small Anim Pract. 1999 Jan;29(1):1-15, ix
  2. Bowles M.  “Stalking stones: An overview of canine and feline urolithiasis”  Veterinary Medicine 2008 Oct;.
  3. Syme HM.  “Stones in cats and dogs: What can be learnt from them?”  Arab Journal of Urology.  2012 September;10(3): 230-239


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