Struvite crystals can form urinary tract stones in cats, resulting in painful elimination. In some cases, the stones can be flushed out of the body or dissolved. In other cases, they must be surgically removed. They occur in both male and female cats.
What Are Struvite Crystals?
Struvite crystals are microscopic crystals that are found in the urine of some cats. Struvite specifically is a material that is composed of magnesium, ammonium, and phosphate. Struvite and struvite crystals can be a normal finding in your cat’s urine at a low level but become problematic when the crystals combine to form grit or stones of varying shapes and sizes. These stones can be found in the urinary bladder, the urethra, or the kidneys.
Symptoms of Struvite Stones in Cats
Some cats may not show symptoms immediately or minimal symptoms and may be found when your veterinarian is performing tests for another condition. Here are the main symptoms that may be present if your cat has struvite stones:
Urinating Outside the Litterbox
Urinating Small Amounts of Urine
In many cases, stones can cause painful inflammation and irritation to the urethra and/or bladder wall and urinary blockage can occur, which is a life-threatening emergency in which a cat can produce very little to no urine.
Frequent Trips to the Litterbox
A cat with crystals or a stone may feel the urgent need to urinate and visit the litterbox frequently in an attempt to pass urine. It may only pass a small amount or no urine, but the pressure and discomfort of the need to urinate will not decrease.
Vocalizing and/or Straining When Urinating
The crystals may have formed a stone that is blocking or partially blocking the urethra making it very uncomfortable for a cat to urinate.
Change in Color or Odor of Urine
Crystals can irritate and inflame the bladder wall causing it to bleed. As result, your cat could pass bloody urine that may have an odor due to an additional infection.
Excessive Grooming and Licking of Genital Area
The pressure of crystals or a stone, and the pain of urination, may trigger a cat to excessively groom and lick its genitals in an effort to relieve the discomfort.
If the crystals have formed a stone, it could affect and inflame the kidneys making the cat depressed and lethargic due to the pain and discomfort it's feeling.
Your cat may not want to eat more because it is uncomfortable as a result of crystals.
Chronic Urinary Infections/Cystitis
Causes of Struvite Crystals
According to VCA Hospitals, “in some cats, struvite bladder stones form as a result of a urinary tract infection, but this is less common in cats than in dogs. In most cases, however, cats develop struvite stones in the absence of an infection. In these cases, the exact cause is unknown. A number of different factors have been found to contribute to these stones, including the formation of concentrated urine, increased urine pH (alkaline urine), and increased levels of magnesium and phosphorus within the urine.”
An underlying cause for the development of struvite crystals is that many cats are reluctant to drink water from bowls. They've evolved over millennia to get most of their moisture from prey. This, partnered with a diet of dry cat food, can lead to crystal development in the cat's urine.
Diagnosing Struvite Crystals in Cats
If you notice any of the symptoms above, it's best to contact your veterinarian immediately. At your veterinary visit, your vet will perform an exam and diagnostics to rule out the known causes of struvite crystals and stones and form a diagnosis. Here are all the ways that your vet can diagnose struvite crystals:
- History: Your veterinarian with the help of the veterinary technician will obtain a history on your cat. This will include your cat's behavior, including any changes to the environment, the cat’s routine and schedule, and any other symptoms you have observed at home.
- Physical Exam: Your veterinarian will perform a physical exam of your pet.
- Bloodwork and Urinalysis: By obtaining and running bloodwork and a urinalysis, your vet will be able to see how your cat’s internal organs are functioning as well as check for dehydration, bladder inflammation, and infection.
- Urine Culture and Susceptibility: A urinalysis sample should ideally be obtained via a cystocentesis which is a procedure where a needle is placed into the urinary bladder through the abdominal wall and a sample of urine is removed. A urine culture test is a method of identifying the specific bacteria that may be causing a urinary tract infection. It involves placing a urine sample on a special medium, incubating the sample so the bacteria can grow, and then identifying the bacteria. A second test (a sensitivity test) is usually conducted to determine the most effective antibiotics to use against the bacteria involved.
- X-Rays and Ultrasound: These are done to assess if the bladder appears abnormal or contains bladder stones. Radiographs are the most effective way to diagnose bladder stones because most bladder stones (including struvites) are visible on radiographs. On radiographs, struvite stones typically look like smooth rocks or pebbles within the bladder. Ultrasound may also be used to visualize bladder stones.
Treatment for struvite stones is based on the underlying cause and is tailored to the individual cat but in most cases, treatments are dissolving the stones via a prescription diet or surgical removal. Additional treatments can include pain medications, diet changes, increasing water intake, anti-spasmodic medication to help the bladder relax, fluid therapy, and reducing stress.
Struvite stones can often be dissolved. The goal is to create more acidic and dilute urine. Canned prescription diets that acidify the urine are ideal, but dry formulations are available for cats who won't eat wet food. Medications that acidify the urine can be used when a cat must be on another type of special diet. If an infection is present, antibiotics will be necessary as well. Your veterinarian will continue to monitor your cat via rechecks (exams, radiographs, urinalysis, and/or ultrasound) until the stones are completely dissolved.
Prognosis for Cats With Struvite Crystals
In some cases, struvite stones cannot be dissolved but have to be physically removed through surgery or other procedures.
If your cat has a urethral obstruction such as a bladder stone, your vet will need to relieve the obstruction quickly. To do this, they will most likely need to sedate or anesthetize your cat and will place a urinary catheter along with managing your pet's pain and other symptoms.
Cats who have developed struvite bladder stones are more likely to experience a recurrence later in life.
How to Prevent Struvite Crystals
You can’t always prevent struvite crystals and stones in your cat's urine. However, there are factors known to increase the chances of your cat having struvite stones which include obesity, decreased water intake, and one of the most common causes, stress. Here are ways to can reduce these factors.
- Activities: Keep your cats active with play and food puzzle toys to help prevent obesity.
- Water: Aid your cat in increasing its water intake to help prevent urinary issues. Encourage your cat to drink by providing various water sources such as fountains, wide and shallow bowls, and have them on each floor in your home. Feeding wet food, a canned urinary prescription diet, and adding water to their food helps to provide your cats with more hydration.
- Resources: Provide multiple, separate key environmental resources such as litter boxes, water, food, hiding spaces, places to perch, resting/sleeping areas, play areas, scratching areas, and toys. This creates an enriched environment that can decrease fear and stress, as well as social tension, competition, and territorial problems in multi-pet households.
- Pheromones: Help reduce your cat's stress. Use products that contain pheromones, such as Feliway, to help create a relaxed cat-friendly environment. Provide your cat with a routine and quiet spaces.
- Litter: Make sure the litter box is set up appropriately. A poor litterbox experience can lead to stress and urinary issues. Use one litter box per cat in the home, plus one extra. Place at least one litter box per floor of your home. The larger the box, the better, meaing that boxes should be 1.5 times the length of your cat. Locate the box in an open, well-ventilated area, and litterboxes should be kept clean.
Struvite Bladder Stones in Cats. VCA Hospitals
Lulich, J P et al. ACVIM Small Animal Consensus Recommendations on the Treatment and Prevention of Uroliths in Dogs and Cats. Journal of Veterinary Internal Medicine, 30,5,1564-1574, 2016, doi:10.1111/jvim.14559
Syme, Harriet M. Stones in Cats and Dogs: What Can Be Learnt from Them?. Arab Journal of Urology, 10,3, 230-9, 2012, doi:10.1016/j.aju.2012.06.006
Gomes, V.d., Ariza, P.C., Borges, N.C. et al. Risk Factors Associated with Feline Urolithiasis. Veterinary Research Communications, 42, 87–94, 2018, doi:10.1007/s11259-018-9710-8