Kidney Stones in Dogs: Causes and Treatment

Kidney stones in dogs are a relatively rare, but potentially serious, condition. It’s estimated that up to 3 percent of dogs are affected by urinary stones, but only 1-2 percent of these are found in the kidney or ureter, making their overall incidence likely to be less than 1 in 3000 dogs. 

Although they are rare, kidney stones can be serious and cause an emergency in some circumstances. Spotting the symptoms early and starting treatment as soon as the condition is diagnosed is key to ensuring dog kidney stones don’t cause kidney failure.

What Are Kidney Stones?

Your dog’s kidneys are part of their upper urinary tract. They’re there to filter waste products from the blood into a fluid we call urine. Urine produced by a kidney collects in the renal pelvis before flowing down a tube called the ureter, into the bladder. From there, the urine is released voluntarily through the urethra to be voided into open air.

A urinary stone (urolith) happens when some of the mineral waste products in the urine come out of solution. Instead of remaining dissolved in the urine, being swept away and released with the urine, they form a solid stone. This happens when the pH of the urine is no longer ideal to keep the minerals dissolved. 

The exact minerals that kidney stones are made of depends on your dog’s diet among other things, but the most common are:

• Struvite (43 percent of stones)
• Calcium oxalate (47 percent of stones)
• Urate
• Cystine
• Silicate

When these stones form in the kidney, we call them nephroliths, renal calculi, or kidney stones. They are relatively rare in dogs, and often an incidental finding – meaning your dog may not show any symptoms, and the stone is seen on an X-ray while investigating an unrelated issue such as hip pain. 

You might be wondering which dogs get kidney stones. There are some breeds of dogs that are more likely to suffer from kidney stones. These are mostly small toy and terrier breeds, including the Yorkshire Terrier, Pugs, Lhasa Apso, Shih Tzu, Bichon Frise, and Pekingese. Some bigger breeds are prone to kidney stones too: Basset Hounds, Mastiffs, Doberman Pinschers, Dalmatians, and English Bulldogs are all over-represented. 

Calcium oxalate stones are more common in males, while struvite stones are more common in females. According to one study, dogs in the South Atlantic region of the USA are more likely to get renal stones.

Kidney Stones vs. Bladder Stones in Dogs

Kidney stones and bladder stones are formed in the same way, and the only difference is where the stone happens to form. Bladder stones are a lot more common in dogs, as minerals have more time to form a stone while it’s sitting in the bladder. 

Bladder stones and kidney stones can have similar symptoms, but bladder stones are more likely to be symptomatic, while kidney stones are more likely to be incidental (they show no symptoms). 

Dogs can also get both bladder stones and kidney stones at the same time.

What Causes Kidney Stones in Dogs?

Kidney stones in dogs occur when minerals in the urine don’t stay dissolved. Instead, they form a solid, stone-like material. This is usually just a few crystals at first, but if these crystals lodge in the kidney they collect more crystals, eventually forming a kidney stone. 

Diet

What foods cause kidney stones in dogs? While there are no specific foods that cause kidney stones in dogs, renal stones are more likely with certain diets. High mineral diets mean there are more minerals to move through the kidneys, increasing the chance of them precipitating out. Some diets also cause acidic or alkaline urine – if the pH of the urine changes, the minerals will not be able to stay dissolved. Diets made by reputable companies that carefully keep to AAFCO recommendations are less likely to cause kidney stones, as they won’t have high mineral levels.

Breeds and Genetics

Dog kidney stones are also more likely in certain breeds – differences in how breeds metabolize proteins or how their kidneys function may explain this. For example, all Dalmatians lack an enzyme for processing uric acid (a by-product of protein digestion), meaning they have high levels of uric acid in their urine. This is highly likely to form urate stones, but low-purine diets can help. The gene that causes this problem has also been found in some other breeds, including Bulldogs. 

Urinary Tract Infections (UTI)

Urinary tract infections can cause struvite stones to form because some bacteria produce urease, an enzyme that causes alkaline urine. Although these stones are usually lower in the urinary tract, as this is where most dogs get an infection, struvite stones are sometimes found in the kidneys. Female dogs are more prone to urine infections than male dogs, but it’s important to keep an eye out for symptoms in most genders. Some anatomical abnormalities increase the risk of urine infections, so it’s a good idea to get repeated UTIs investigated.

Highly Concentrated Urine

The more concentrated the urine is, the less water is available to dissolve the minerals, increasing the risk of them precipitating out and forming a kidney stone. Highly concentrated urine can happen if dogs are dehydrated, perhaps on a hot day when their water bowl runs dry or after prolonged exercise. Dry food diets do not cause dehydration, but they do mean that dogs need to drink more of their water intake, rather than getting it in their diet. It’s always important that dogs have access to plenty of fresh water, but especially on hot days, during exercise, or if their diet is dry.

Symptoms of Kidney Stones in Dogs

Some dogs get symptoms of kidney stones, but some do not. Whether or not a kidney stone causes symptoms is often related to exactly where in the kidney it forms, as well as whether it prevents urine from flowing out of the kidney. 

Some renal calculi can form in such a way that they block the ureter and cause a build-up of urine in the kidney – this is painful and an emergency situation. On the other hand, some renal calculi will form in the part of the kidney called the renal pelvis and won’t obstruct anything, making it unlikely that they cause any symptoms. 

Dogs with kidney stones may have some of the following symptoms, which are approximately in order of least serious to most serious:

• Recurrent urinary infections
• Change in urine output
• Bloody urine
• Abdominal pain
• Fever
• Poor appetite
• Weight loss
• Vomiting

Your dog may have some of the symptoms, none of the symptoms, or all of them. 

Diagnosing Kidney Stones in Dogs

If your vet suspects kidney stones in your dog, they will first undertake a physical exam, looking for hydration status, abdominal pain, and any concurrent diseases. 

They will then recommend urine testing. They’re looking for the acidity of the urine, which may hint at what sort of stones could be present, as well as urine infections, which not only have similar symptoms but can cause struvite stones to appear. Your dog’s urine sample may also contain crystals of minerals – these are the individual molecules of minerals that haven’t joined to a stone. It’s possible to get crystals without stones, and even possible (though rare) to get stones without seeing crystals. Your vet can examine the crystals under the microscope to tell what sort of stones may be forming in your dog’s urinary tract.

Next, your vet will recommend imaging. X-rays are really useful for diagnosing kidney stones, as most of them show up well on X-ray. However, ultrasound is also useful, as it can show the stones that aren’t easily visible on X-ray as well as show whether there’s a build-up of fluid in the kidney, suggesting the stone is causing a blockage. In most cases, vets will do both an ultrasound and X-ray to get as much information as possible about your dog’s renal stones.

Kidney Stones in Dogs Treatment

Once your dog has been diagnosed with kidney stones, your vet will talk to you about treatment. There are several treatment options we will go into below. These include:

• Dissolution diets (dissolving the stone)
• Surgical removal
• Stenting
• Endoscopic removal
• Extracorporeal shockwave lithotripsy (shockwave therapy)

Dissolving the stone

Unless your dog’s renal stone is so large that it’s squashing the kidney, or in a place where it’s causing a blockage, your vet will probably recommend a dissolution diet. This is a prescription diet that is designed to dissolve the stone – the exact diet will depend on the type of stone your dog has formed. 

The diet changes the pH of the urine to something that encourages the minerals to dissolve again. It may also encourage dilute urine to help the stones to dissolve. You will also need to encourage water intake in your dog to make the urine as dilute as possible. 

Surgical removal

Surgical removal of stones in the kidneys should only be considered if they are causing a severe problem and aren’t responding to other, non-invasive methods. Removing the stone will involve opening up the kidney and/or ureter, both of which are extremely delicate structures. This operation will likely involve referral to a specialist surgical team. If the stone isn’t dissolving with diet, or if it’s causing a blockage or has become very large, your vet may suggest surgery as the best option to treat your dog’s kidney stones.

Stenting

Stenting doesn’t treat the kidney stone itself, but it can bypass an obstruction caused by the stone and allow the dissolution time to do its work. A stent involves inflating a small balloon in your dog’s ureter, making the tube larger and allowing urine to flow past the blockage. It allows the medicated urine to flow past the stone, encouraging it to dissolve.

Endoscopic removal

In some cases, where the stone is too large for ultrasonic removal, removal of the stones using an endoscope is possible. This is a non-invasive surgical removal – your dog will likely need to be referred to a specialist surgical team and will still need a general anesthetic. This is ‘keyhole surgery’, and it means that recovery is quicker. 

Shockwave therapy

For some stones, a useful non-invasive procedure is ‘extracorporeal shockwave lithotripsy’, known as EWSL or shockwave therapy. Shockwave therapy involves using a machine that generates shockwaves, which are directed at the stone. The stone breaks up under the influence of the shockwaves. Once the stone is smaller, it can be passed, or the obstruction is relieved, and the stones can be dissolved with diet. Shockwave therapy can only be performed if the stone is less than 1.5cm in diameter. 

Home remedies and homeopathic therapy

There are no recommended home remedies and homeopathic therapies for kidney stones in dogs. Kidney stones can become an emergency and even be fatal if they start to cause an obstruction, so it’s important to get recommended treatment as soon as you notice symptoms.

Cost to Treat Kidney Stones in Dogs

Kidney stone treatment costs vary greatly, depending on what treatment is necessary. First, you’ll need some investigations and exams, likely to be in the region of $200-$800 range. 

Dissolution diets, while more expensive than usual foods, are still a relatively cheap option. An 8.5lb bag costs around $50. 

However, when renal stones are causing serious problems, treatment costs rise. Your pup might need hospitalization, emergency exams, and specialist surgery with expensive equipment. Costs will reach into the thousands. It’s really important that you communicate any budgetary constraints to your vet as soon as possible, as they may be able to recommend an alternative route.

How to Prevent Dog Kidney Stones

For most dogs, kidney stones are so rare that you don’t need to do anything to prevent them. Keeping your dog on a complete and balanced healthy diet made by a reputable company will keep their dietary mineral consumption within recommended ranges. Ensuring they always have plenty of water and treating any urine infections as soon as you notice signs are both important, too. 

However, there are some dogs that are at such an increased risk that prevention is sensible. Dalmatians – and any dogs known to have the gene mutation that causes the overproduction of uric acid – benefit from being on a low-purine diet to prevent urinary stone formation. Your vet can help to recommend a low-purine diet to help to prevent kidney stones in Dalmatians. 

If your dog has previously had urinary stones, they’re at an increased risk of getting them again. Once the stone is removed, they may need an ongoing stone prevention diet.