Uroliths And Bladder Stones in Cats

uroliths and bladder stones in cats
Cats may often drink from taps

Symptoms of urolithiasis are:

  • straining to pass urine
  • blood in the urine
  • urinating in inappropriate places outside the litter box
  • licking the genitals or base of the tail excessively
  • lethargy
  • vocalization upon urination, indicating pain
  • diminished frequency or volume of urine passed
  • passing no urine


If you find your cat is not passing urine upon straining, it is important to talk to your veterinarian promptly in case of a blockage.


Types of urine crystals

The two most common kind of urinary crystals that affect cats are:


Struvite crystals are composed of magnesium, ammonium and phosphate. They are crystal-like formations that are small in size but can continue to grow and merge with other small stones to form larger blockages. When cats have struvite plugs in their urethra (the tube that extends from the bladder to the outside of the body to discharge urine), they are typically comprised of several joined crystals.


Formation of these crystals is generally influenced by metabolic factors, including the concentration of the urine, its pH (acidity/alkalinity) and excessive consumption of certain minerals and fiber.  In some cases a bacterial infection can trigger the changes that cause formation of crystals and stones.

Acidifying the body leads to an acid urine pH and more calcium loss into the urine, and both factor in the development of a calcium oxalate stone. Most bladder stones formed in cats today are calcium oxalate stones: they are most common in cats between ages 5 and 14 years and around 35% of cats with calcium oxalate bladder stones have elevated blood calcium (hypercalcemia). Cats with calcium oxalate stones tend not to have bladder infections but are commonly found to have acidic urine pH on their urinalysis.

It is thought that current lifestyles for cats, including domestication and indoor living, together with a change in pet food formulations, have led to an increase in cases involving urinary crystals. It is thought that some of the contributing factors may include:

  • obesity
  • indoor living
  • insufficient water intake
  • high-salt diets
  • stress/anxiety
  • trauma
  • infection

Always seek the professional opinion of your veterinarian if you suspect your cat is suffering from urinary difficulties.


What treatments are available?

In mild cases of struvite crystals without blockage (small stones), the veterinarian will often prescribe antibiotics for a bladder infection (bacterial cystitis, when present) and adequate pain relief, as the cat can become very uncomfortable. It may be necessary to nutritionally manage the condition using a prescription diet especially designed to dissolve the crystals. Where there is idiopathic cystitis concurrently, a wet diet may be recommended. However, in most cases. the dry product is effective alongside unrestricted access to water.


It is usual to continue on a prescription diet for at least twelve weeks after complete resolution and dissolution of any crystals or stones in the urinary tract. Your veterinarian can periodically test your cat’s urine to determine the presence of any conditions which may lead to crystals and stones.

If symptoms re-occur when the cat returns to its normal diet, your vet may recommend long-term feeding of a prescription diet. These are fully balanced for adult cats and will provide all the nutrients they need for general health in addition to the needed support for urinary tract health.


In the case of calcium oxalate stones, these cannot be dissolved through diet and in many cases require removal through flushing or surgical intervention. In some practices, there is the option of using laser treatment to dissolve the stones but this is as yet not widely available. If your cat has had treatment for Calcium Oxalate stones, you are likely to be advised to continue on a non-acidifying diet that minimizes calcium oxalates in urine. These specialized diets will have a normal calcium content, a moderate magnesium content and citrate to bind urinary calcium.

In all cases where a blockage is present, either catheterization under general anesthetic is required to flush through and dislodge the obstruction or surgical intervention may be necessary to remove larger stones from the urinary tract and bladder. Animals requiring such treatment are usually hospitalized for several days so that the vet can monitor urination, after surgery. Again, these cats may require special dietary management once discharged, to prevent further reformation of stones.

Unfortunately, crystals may recur, so it is important to adhere to any vet prescribed diet and to continually monitor your cat for changes in its behavior or urinary habits. Although it may not always be possible to always prevent these conditions from recurring, taking some practical steps can increase the odds in your cat's favor. If in doubt, always check with your veterinarian. Visit us again soon for additional features on the prevention of urinary stones in cats.

Image courtesy of A.Daff