Feline Bladder Stones

What is it?

Struvite is a urinary mineral consisting of magnesium, ammonium and phosphate. These substances are commonly found in urine, and when present in high concentrations, they can bind together and form crystals, which are microscopic. There are several factors contributing to the formation of crystals, including the pH of the urine, and the dilution of the urine. These crystals may further bind together to form stones, which can be seen with the naked eye. The crystals or small stones may also cause irritation to the bladder lining and the urethra, which can result in typical clinical signs of blood in the urine, straining to urinate, urinating small volumes more frequently, or urinating in inappropriate or unusual places.

In cats, these crystals are usually not associated with a bacterial infection, although they may predispose the cat to getting one.

In cats, the most concerning risk of crystals in the urine is that they can bind together with mucous and other cells and form a plug that blocks the urethra, or small stones can block the urethra, so no urine can come out of the bladder. This is a life-threatening condition, because if urine cannot escape the body, the toxic waste products build up quickly in the blood stream and lead to severe neurological and cardiovascular changes. If your cat ever tries to urinate without producing any urine, this is an emergency and your cat needs to see the vet immediately. This is why managing the crystals and preventing their formation is so important.

3 Stones in the bladdre (yellow arrow)

How is it Diagnosed?

The common clinical signs of bladder stones in cats are similar to several other diseases, including urinary tract infections, bladder cancer, idiopathic cystitis (inflammation of the bladder with no detectable cause), stress-induced cystitis, or even kidney disease. It is important to rule these out while also checking for the presence of crystals or stones. 

Firstly, a thorough physical examination is performed. We can feel for the bladder and determine if it is large and distended, which may indicate a blockage or partial blockage, or if it is small and empty, which is typical of patients with irritation of the bladder. 

A urine sample can be taken, either from the animal urinating, or by using a needle to take urine directly from the bladder. A sample directly from the bladder is most beneficial to accurately diagnose the problem, especially if an infection is present. This sample can be checked under the microscope for the presence of crystals, and can also be checked for bacteria. The pH is also checked, as well as the presence of blood or inflammatory cells.

As mentioned, it is important to rule out other causes of the signs seen, so an ultrasound and/or x-rays should be performed. This will allow us to see any masses or stones in the bladder, and also check the kidneys. Not all types of stones are visible on radiograph, so the combination of both x-ray and ultrasound will give the best chance at diagnosis. 

A blood test should also be performed to check how the kidneys are functioning, and check for signs of inflammation and systemic disease.

What is the treatment?

  • Surgery
    • If large stones are present, they may need to be removed surgically. This is usually required if a blockage has occurred or if the stones are formed from non-dissolvable minerals. Similarly, if the bladder has been blocked by the collection of crystals and other materials, a urinary catheter will need to be placed to dislodge the blockage and empty the bladder. 
  • Dissolution Prescription Diet 
    • Crystals and some stones can be dissolved by special diets. These diets have a specific balance of minerals to prevent or minimise crystal formation and adjust the acidity of the urine. It is very important to ONLY feed this food if it has been prescribed to you. Any other food may prevent the diet from working. Most cats will need to remain on some form of urinary diet for life to reduce the risk of life-threatening blockages. 
  • Antibiotics 
    • If an infection is present as well, your cat will need antibiotics to treat this. 
  • Pain relief and anti-inflammatory 
    • By the time stones or crystals are diagnosed, the bladder is usually quite irritated and sore. Many cats will need some pain relief to make them feel more comfortable and settle down the inflammation.

What do I need to do?

  • Ensure you feed only the food prescribed to you by the veterinarian 
    • The diets work by dissolving crystals and altering the pH of the urine, so other foods may interfere with this and change the urine pH, making the diet ineffective and putting your cat at risk of further complications 
  • Increase your cats water intake as much as possible. 
    • This can include using water fountains designed for cats, as they often prefer to drink moving water. 
  • Monitor for signs of urinary irritation or blockage
    • Urinary irritation: straining to urinate, blood in the urine, having accidents outside the litterbox, or overgrooming their genitals. 
    • Blockage: Remember that if a cat is straining to urinate without producing any urine, this is a medical emergency
  • Don’t stress! 
    • Diet therapy is very successful, and most cats remain very well controlled once they are on an appropriate diet.

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