Pet Tips

Bladder stones in dogs – Pet tip 127

Bladder stones, or uroliths, are increasingly common in pets. Often the first signs of uroliths is straining to urinate and blood in the urine, or recurrent bladder infections. If a stone is small enough to leave the bladder but large enough to block the urethra, the most serious consequence is uremic poisoning from urine that is trapped in the bladder. Stones are irritating to the delicate wall of the bladder and cause inflammation as well as predisposing to infections. The most common stone types are struvite and calcium oxalate. Their mineral composition and the conditions under which they form are completely different, as are the approaches to their prevention. Often an animal will have crystals in its urine, but these crystals are not always of the same type as the stone(s), nor do they necessarily lead to formation of stones. So the only way to determine the type of stone is to analyze a sample that has been passed naturally or removed via surgery.

Struvites have a mineral matrix consisting of magnesium, ammonium and phosphate. Struvite crystals are often found in normal urine but become a problem when there is a concurrent infection with certain bacteria which can digest the by-products of normal protein metabolism and generate ammonia. (The cocker spaniel is an exception to this rule in that it can form stones in sterile urine.) Ammonia promotes formation of struvites in three ways. First, it is directly toxic and irritating to the bladder and creates inflammation with influx of inflammatory proteins which serve as organic building material for a struvite stone. Secondly, ammonia creates a high pH which is the necessary condition for struvite formation. Thirdly, the ammonium ion serves as a mineral building block of the stones. As the stone forms, bacteria are trapped inside and become active as they are released. Struvite stones can be removed in three ways. Urohydropropulsion involves flushing the bladder with sterile saline and forcing the stones out together with urine, and works for smaller stones which do not risk blocking the urethra. Most (85%) cases of struvite affect female dogs since they are more prone to bladder infections, but their urethra is also wide enough to pass a stone up to 3-4mm. Larger stones can be surgically removed by cutting into the bladder. Finally, struvites can be dissolved through feeding a special diet together with antibiotic treatment which is necessary to kill bacteria as they are released from the dissolving stone. Dissolution diets are high in fat and salt and not suitable for dogs with pancreatitis, heart disease, kidney disease or high blood pressure; nor should they be fed for more than 6 months. Prevention and timely treatment of urinary tract infections with appropriate antibiotics is key to preventing formation of struvites. If your dog is diagnosed with a bladder infection, your veterinarian will offer to perform a culture and sensitivity test on the urine. This shows which bacteria are causing the infection and which antibiotics are best to eliminate them, and is a step well worth taking to prevent recurrence of the infection.

Calcium oxalate stones form in acidic urine, and diet plays a large role in their formation. Excess calcium in the diet and supplementation with Vitamin D (which facilitates uptake of calcium) increase the amount of calcium which ends up in the urine; peanuts and peanut butter provide oxalate, another mineral building block of the stones; adding urinary aciFisdifiers creates an acidic pH which is necessary for these stones to form. It is not uncommon for calcium oxalate stones to form as a result of overly aggressive therapy aimed and preventing struvites by adding acidifiers to the diet. (Dissolution diets for struvites are already acidifying and require no supplementation. Vitamin C, often given to dogs, is not required to begin with: unlike humans and some other species, dogs synthesize their own.) Some breeds are predisposed to forming calcium oxalate: the miniature schnauzer, Lhasa apso, Yorkshire terrier, bichon fries, Shih Tzu, and miniature poodle. A substance called nephrocalcin is needed to prevent formation of calcium oxalate stones, and dogs of the above breeds are often deficient in this substance; the defect is likely genetic. Some medications increase the risk of calcium oxalate formation because they increase the amount of calcium in the urine. Medications that should be avoided in dogs prone to forming calcium oxalate are: prednisone and other corticosteroids (used to treat inflammatory and immune-mediated diseases); and furosemide, a diuretic mostly used in treatment of heart failure.

Unlike the case with struvites, most dogs that form calcium oxalate stones are males. However, some dogs are prone to forming stones of both types. If this is the case, the priority is usually to prevent the occurrence of calcium oxalate since this type of stone cannot be dissolved. The most simple approach to prevention of either type of stone is dilution. If an animal drinks enough water to keep their urine dilute, crystals have no opportunity to form stones. Clean water must be easily available and canned diets are preferred over dry kibble. The good news is that canned diets do not put the animal at greater risk for dental disease. If a dog is used to eating only or mostly kibble, it can be soaked in warm water prior to feeding.

By Veronica Gventsadze – writer

7 Responses to this Article, So Far

  1. Avatar Laura says:

    My male dog age 8 have calcium oxalate bladder stones that have to be removed surgically. VET wants me to put him on Royal Canin urinary SO food to prevent future reoccurrences. Is there any evidence that this really helps with Ca oxalate stone. His urine PH is too acidic at 6.0. Goal is to get it up to 6.9.
    I’d like to continue to give him the kibble he likes (no by product, corn etc…) which I’ve been adding lots of water too since he’s not a big drinker.

  2. Avatar Barbara says:

    Hi, my 10 year old ( a very picky eater) male also had same surgery three weeks ago and my vet instructed me to do the same. The canned Royal Canin is too expensive for me to use it on a daily basis. My vet reluctantly allowed me to purchase the dry dog food (slightly less costly) which I have been adding lots of water as well as he is also not a big drinker. He does not like it. He misses his dry kibble He is also suffering from “treat” withdrawal and is confused and depressed as to why he is being “punished”. Very very sad. I did bake the canned dog food in thin slices, which is the only “treat” I have given him. I need suggestions and help too. Plain human food? Turkey etc??

    • Avatar Marko says:

      I encourage you to post this on our pet forum for free. We have wonderful members there with much more knowledge on this topic than I have.
      Good luck!

  3. Avatar Laura says:

    It’s been a year since my dog had his CA oxalate stones removed and I’m happy to report that he’s had no further stone and is maintaining urine PH 6.9-7.0. I have been making him homemade meals. As a Dietitian, I decided to tx my dog diet like patient and put him on a low oxalate diet. He receives two meals daily which include: 3 oz of lean beef, chicken or turkey, 1/4-1/3 cup white rice and 1/4 cup of varying vegetables (cauliflower, peas, brussels sprouts, black eyed peas, cabbage). 1/2 oz of liver daily. I add Hi potency B-comlex 1 and 1/2 capsules daily (have to open and add powder to meals(only B vitamin 50mg) and calcuim citrate pure powder (1 tsp added to his meal twice daily) and add fish oil daily. I still give him treats, but only chicken breasts. I also make him homemade chicken broth which he drinks after his walks. He still won’t drink water. Hope that helps. I refused to feed my dog that horrible Royal canin.

  4. Avatar Chazz says:

    Our dog had CA oxalate stones surgically removed a yr ago. After the surgery we put him on Royal Canine SO dry food. Then over Cmas this year we noticed he was straining to pee. Took him to a new vet and after xrays he had more stones. So frustrating since it’s only been a year. They tried to surgically flush them out but soon realized he had one lodged in his penis. He had to be rushed to a Specialty Surgeon, since the next step of surgery would be too complex for our general Vet. We had to spend $6k to have the stones in his bladder removed and to also create a new pee hole for him. The new pee hole is behind his penis and has a larger opening to help him pass future stones- He now pees like a female dog. The specialist after reviewing all our records made the comment “that we did not have proper aftercare after his first stone removal surgery”. Royal Canine is not formulated for CA oxalate stones and if at all possible you should always opt for the canned food since it has more moisture. Water in the dog’s diet is very important to help flush out the extra minerals that create stones in the urine. There are also mediations that can be given for extended periods of time to help prevent these types of stones. Our old vet never mentioned any of this to us. Our dog is still recovering from surgery but we have already switched him to the canned Hill U/D diet, which I add a whole lot of extra bottled water to and blend up- He seems to love it. He pees a lot more than he ever did, which is great news b/c it means that he is getting plenty of fluids to help flush his kidneys & bladder. Moral of our story- make sure if you are using a RX diet for your dog make sure it’s the right formulation for the type of stones they get. ALSO- I know canned food can be pricey, but it’s much better for your dog and maybe can prevent you having to pay $6 grand like we did…

    • Avatar Marko says:

      Chazz! Thank you SO much for sharing your story and for treating your pet like a family member. Although I too think of pets as family members, not everyone does.
      I 100% agree with everything you wrote and the second vet, as far as my knowledge goes (I’m not a vet but do know a fair bit) is bang on.
      The only thing I’d like to add is that PET INSURANCE is often a great move when you first get your pet as it can avoid costly bills like this. Many people have terrible financial stresses at this time and would not be able to find this kind of cash or choose to go into debt for their pet.
      Thank you for being such a wonderful pet owner and for sharing this experience!

      • Avatar Chazz says:

        Hi Marko! Thanks for so much for the compliments! Our pets are totally our family members and I can’t imagine treating them otherwise. However I do understand that money can play a big issue in the ongoing treatment for chronic conditions in animals for many pet owners- a lot of times it can be a deciding factor on whether or not the animal will live to see another day (so sad!). And although we did not opt for Pet Insurance for our doggie when we got him, if I could do it all over again I SO would. And anyone I know who gets a new pet I always tell them that they should def look into insurance. By the time someone had informed us of pet insurance it was too late, our dog had too many chronic conditions to be covered by many carriers. Not only does he have bladder issues but he has severe skin allergies and we have spent lots of $$$ on him over the years at the vet. If we had known about pet insurance when we first got him it would have saved us a lot of money. But at this point it doesn’t matter, because I love him lots and it’s all worth it to us!

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