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Bladder and kidney stones are hardened accumulations of minerals found in urine. Common minerals involved include struvite, calcium oxalate, and urate. Dogs and cats can develop stones anywhere in the urinary tract. Stones can form in many different shapes and sizes.
Certain breeds of animals may be more likely to form certain kinds of stones. Dalmatians, for example, are more likely to develop urate stones.
Stones can have sharp edges and can irritate or become embedded in the lining of the bladder, causing the tissue to become thickened and inflamed. They can also form inside the kidneys.
Stones can cause serious problems when they lodge in the ureters (the thin tubes connecting each kidney to the bladder) or the urethra (the narrow tube that allows urine to flow from the bladder out of the body). When the normal flow of urine from the kidney to the bladder is obstructed, urine (and pressure) can build up in the kidney, potentially causing kidney infections or kidney failure.
If a stone obstructs the urethra, the pet is unable to urinate, and the urine builds up inside the urinary tract. This occurs more commonly in male pets because, compared with females, they have a longer and very narrow urethra. When pets are unable to urinate, it’s a medical emergency, and a veterinarian should see the pet immediately.
Stones are often caused by an underlying condition that alters the balance of minerals or other substances that are excreted in the urine. Factors that could influence the risk for the formation of stones include:
⦁ Type of food the pet is eating
⦁ Urinary tract infections
⦁ Metabolic diseases
⦁ Genetic predisposition (breed of animal)
Most stones are found in the bladder. Pets with bladder stones may show no signs at all or may exhibit signs such as the following:
⦁ More frequent urination
⦁ Blood in the urine
⦁ Urinary accidents
⦁ Recurring urinary tract infections
Signs of a possible urinary blockage include:
⦁ Straining to urinate
⦁ Inability to urinate
⦁ Crying in the litterbox
⦁ Vomiting
⦁ Anorexia
⦁ Painful abdomen
⦁ Lethargy (tiredness)
Pets with kidney stones may show no signs or may have persistent blood in the urine. If a blockage affects the kidneys, the pet may have pain near the middle of the spine (where the kidneys are located) or may drink and urinate more.
Some vets may be able to feel stones in the bladder by applying gentle pressure with their hands. In most cases, an abdominal radiograph (x-ray) is required. An abdominal ultrasound may also be helpful to visualize stones.
If the urethra is obstructed with a stone, the vet will usually be able to feel a firm bladder, and the pet may have signs of pain.
Testing the urine is helpful to determine if a urinary tract infection is present. Sometimes crystals may be found in the urine, which may provide a clue as to the type of stone involved. Still, the only way to identify the type of stone with certainty is to send sample stones to a laboratory for analysis. This is important because treatment will vary depending on the stone.
Blood tests will also aid in a diagnosis. In some cases, an underlying metabolic disease can cause the build-up of certain minerals (e.g. calcium) in your dog’s blood and urine which causes the formation of stones. This will also need to be addressed to prevent the stones reforming.
In pets with blockages, emergency surgery is usually required. If the pet is not blocked, some stones can be dissolved by feeding the pet a special diet. This food, available only through veterinarians, will help modify the urine pH and dissolve the stones.
Some types of stones cannot be dissolved by diet and must be removed from the bladder using other methods, including:
⦁ Voiding urohydropropulsion: While the pet is sedated, small stones may be flushed out by filling the bladder with fluid and applying pressure to empty it (only works for small stones)
⦁ Surgery: The bladder is opened through the abdomen, and the stones are removed
While kidney stones may be removed by surgery, this procedure may affect kidney function. If the kidney stones are not causing any problems often these will be monitored by repeated x-rays and urine tests.
Once stones are removed, they are generally submitted to a diagnostic laboratory so their type/composition can be determined. Once the stone composition has been determined by lab analysis, pets may need to be fed a special diet and/or given medication for the rest of their lives to help prevent recurrence. The type of diet and medication will be advised by your Veterinarian.
Frequent monitoring of your dog’s urine is needed, especially in the early stages after diagnosis of bladder stones or crystals. If your pet requires surgery to remove bladder stones or to unblock the urethra they will need to be seen a few times in the first few weeks to ensure they are recovering well. Their urine will need to be checked within 1-2 weeks to ensure the crystals or other signs of bladder stones are resolving. After this they will need a check-up at 1 month and 3 months to monitor for signs of urinary issues. An x-ray or ultrasound will be repeated to ensure no new bladder stones or crystals are forming.
If your dog is doing well after the first few months, they will need less frequent monitoring but will still require 6 monthly consultations with your Veterinarian to continue to dispense medication, prescription diets and to closely monitor your pet. After the initial tests your Veterinarian will advise when repeat testing is required depending on how your dog is doing at home, in general this will involve:
⦁ Repeat Urinalysis (urine tests) + urine culture (if needed) – every 6 months
⦁ General Blood test Monitoring – every 6-12 months (to monitor organ function) – more frequently if they are on medication or had any kidney issues.
⦁ Repeat Abdominal Ultrasound or X-ray – every 6-12 months
If you have any concerns or notice any changes in your pet’s condition, please contact your Veterinarian immediately to make a recheck appointment.
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