Did you know that your pet can suffer from kidney stones, just like a human? What causes kidney stones can differ depending on your pet’s condition, and the mineral makeup of the kidney stones can determine what treatment your vet may recommend. Here, we explore why pets develop kidney stones, what causes kidney stones, and how you and your family vet can work together to help your best friend live a long and healthy life.

What Are Kidney Stones?

The kidney is composed of nephrons, each consisting of capillaries and a series of tubes through which fluid flows as urine is produced. The nephron tubes drain into ducts, and these ducts eventually enter the pelvis. In the pelvis, the ducts drain into another tube called the ureter. Kidney stones (or nephroliths) are clusters of crystals or stones that develop in the kidneys or urinary tract. Nephroliths (or fragments of them) can develop in the kidneys and pass through your pet’s system of kidney tubes into the ureter. If the stone blocks the ureter, serious complications can develop if left untreated.

kidney stone

Why Are Kidney Stones Important?

Just because your pet doesn’t appear to be in pain doesn’t mean that kidney stones aren’t important. If the kidney stone gets very large, or if pieces break off and lodge in the ureter, it can be very painful for your pet, even if they don’t show it. The kidney may swell and become damaged if the ureter is blocked by a stone.

If this happens simultaneously to both kidneys, and the blockage persists, your pet can become very ill from the disrupted flow of urine. For example, if your pet has a bacterial urinary tract infection that keeps coming back, or stubbornly refuses to clear up, you may need to eliminate a kidney stone in order to resolve the infection. Urinary obstructions can become life-threatening emergencies that must be treated–if you notice changes in your pet’s urination, along with any of the symptoms discussed below, you should consult your family veterinarian right away.

Is My Pet Susceptible?

Both dogs and cats are susceptible to kidney stones. However, some breeds are more likely to develop kidney stones than others. In cats, breeds like the domestic shorthair and longhair, Persian, and Siamese are more likely to develop kidney stones. Cats that are middle-aged or older are more likely to be affected by kidney stones than kittens.

Dog breeds like the Lhasa Apso, miniature schnauzer, Shih Tzu, and Yorkshire terrier have an increased risk of kidney stones. Some breeds are even more likely to develop certain types of stones than others. Stones containing uric acid typically affect Dalmatians, Yorkshire terriers, and English bulldogs, while kidney stones caused by calcium and oxalic acid are more likely to be found in Lhasa Apsos and miniature poodles. If your pet is susceptible to kidney stones, they may form stones multiple times, despite ordinary precautions taken to prevent them.

labrador dog

Symptoms

Many pets display no apparent signs of kidney stones. The nephroliths often go undetected until diagnostic testing is done for other medical issues. Your vet may find kidney stones while examining your pet for an unrelated condition. Some obvious symptoms of kidney stones may include blood in their urine (also known as hematuria), vomiting, recurring urinary tract infections, painful and difficult urination (called dysuria), and frequent urination with little  production volume. Other symptoms may occur, but vary on what causes the kidney stones.

If you suspect kidney stones in your pet, you will want to keep an eye out for those symptoms listed above. You may also want to watch for fever, abdominal discomfort, lethargy, and weight loss.

What Causes Kidney Stones?

There are a number of causes and risk factors that may contribute to the development of kidney stones. In some cases, there may be an oversaturation of stone-forming materials in your pet’s urine. Other potential causes may include increased calcium levels in the urine and blood, diets that produce high (alkaline) urine pH, or recurring urinary tract infections.

Types Of Kidney Stones

The type of stone depends on what causes kidney stones have. Stones of calcium oxalate are commonly developed in the bladder and are one of the most common types of kidney stones. Stones that form in the bladder or kidney due to chronic bacterial infection are called struvite. Struvite stones are commonly composed of magnesium, ammonium, and phosphate. Metabolic stones are more common than those caused by infection (for both dogs and cats) and are formed due to a blood or urinary imbalance. Urate stones are most commonly the result of a genetic abnormality that causes a defect in the metabolism of uric acid.

Diagnosis

Many kidney stones show up on X-rays, but smaller stones may be hidden by whatever else is in your pet’s belly and intestines. What causes kidney stones could also affect the X-rays imaging. Some stones just don’t show up well on radiographs. For example, urate stones, which Dalmatian dogs are especially susceptible to, don’t consistently image well, so simple X-rays may not offer enough information for your vet to make a definitive diagnosis. You will need to give your veterinarian a thorough history of your pet’s health, including the onset and nature of the symptoms.

Once a stone is diagnosed, however, your vet will likely want to conduct more tests to determine the type of kidney stone you’re dealing with, predict the impact that the stone may have on your pet’s health, and see what other conditions (if any) may increase the risk of what causes kidney stones in your pet.

Some tests your vet may recommend include:

  • A complete blood count (CBC)
  • Blood chemistry with electrolytes (testing for evidence of kidney disease)
  • Urinalysis (may predict kidney disease, bacterial infection, or crystals that may help predict stone type)
  • Urine culture with susceptibility (to identify potential bacterial infections)
  • Systemic blood pressure
  • Abdominal radiographs (X-rays)

Your vet may also recommend an abdominal ultrasound to verify the location of any stones and the suspected degree of any obstructions, or a contrast radiography. A contrast radiography uses dye to make the images show up better on an X-ray, and may be needed to confirm blockage and show whether your pet’s urine production is balanced between both kidneys. In order to confirm the diagnosis, identify the mineral content of the stones, and develop an effective course of treatment, your vet may need to retrieve pieces of the kidney stones for analysis. For dogs, this can be achieved by performing a procedure known as extracorporeal shock wave lithotripsy (ESWL), in which stones are broken up within the urinary tract using sound waves.

Treatment

A small kidney stone that allows normal urine flow may be one that your vet watches closely but leaves untreated. However, the larger the stone, the more likely that your vet will recommend treatment.

What causes kidney stones is important in determining which treatment options are available for your pet. With some types of stones, your vet may recommend conservative treatment, with a combination of antibiotics, diet, and plenty of fluids. Dissolving kidney stones often takes months, but any early reduction in size is a good sign. It’s likely that your pet will not need more specific treatment in order to remove the stones.

Medical efforts to dissolve kidney stones are usually safer than surgery, but won’t work for all stones. Veterinary urologists may offer special techniques to break stones up into smaller pieces that can more easily pass out of the body through the urine. Some of these treatments, such as ESWL, may not be recommended for cats because the stone fragments tend to lodge in the narrow feline ureters. However, veterinary specialists continue to develop better treatments for cat kidney stones based upon advanced techniques usually used in humans.

For emergency situations where the ureters are blocked, your vet might recommend by-pass surgery that re-routes urine around the blocked ureters. Any surgery has its risks, and kidney surgery does risk permanently damaging the affected kidney, even if the surgery goes smoothly. You may ask your vet if surgery is the best option for your pet, or if there may be a different treatment to try.

Managing Your Pet’s Kidney Stones

Because kidney stones tend to recur once your pet has had them, routine monitoring is important. What causes kidney stones may determine the routine you follow moving forward–if your vet suspects oxalate kidney stones, she may suggest a special diet and medications to reduce or slow stone growth. Encouraging your pet to drink more water, or take more water in the form of canned food, will help dilute the urine and reduce the amount of mineral available to add to a stone.

Your vet will also want to balance the dietary needs of any other illness your pet has, such as diabetes or gastrointestinal disease. If your vet suspects an underlying cause for the stones, such as infection, resolving that primary issue will be a key part of any treatment or management plan.

Even if the stones don’t seem to be active or causing any complications, your vet will likely recommend that you continue to monitor your pet’s condition with tests for kidney function, urine quality, and X-rays or ultrasounds. Your vet will want to make sure that the prevention strategy is working, and that any stones that remain are not growing or causing any complications for your pet.

checking puppy's heartbeat using a stethoscope

Conclusion

What causes kidney stones is important as determining the type of stone may help your vet put together an effective treatment plan for your pet. If stones have been removed, either through medical dissolution or through surgery, developing and sticking to a plan to monitor for any recurrence is critical to keeping your best friend healthy. If you have any questions or concerns about your pet’s health, you should always consult your family vet–they are your best resource to ensure the health and well-being of your pets.