May 3, 2025, 12:50 pm | Read time: 5 minutes
Struvite stones can cause serious health problems in cats — and sometimes even lead to life-threatening emergencies. Learn why timely action is crucial and what treatment options are available here at PETBOOK.
Struvite stones, medically known as ammonium magnesium phosphate stones, are among the most common bladder stones in cats. They usually form in the bladder and vary in severity from uncomfortable to painful for the animal. They are one of the most common causes of urinary tract diseases in cats. If detected early, they can be successfully treated — sometimes a change in diet is sufficient, but in some cases, surgery is necessary.
How Struvite Stones Form in Cats
Two main factors promote the formation of struvite stones: insufficient fluid intake and an unfavorable composition of food. Increased intake of proteins and minerals such as magnesium and phosphorus can raise the urine pH level and increase concentration in the urine. This encourages the formation of crystals that can combine into stones. Other risk factors include obesity and lack of exercise — outdoor cats are less affected than indoor cats. 1
Smaller particles are referred to as urinary grit, while larger formations are called struvite stones. Both are usually indicators of lower urinary tract diseases, which are collectively known as FLUTD (Feline Lower Urinary Tract Disease), including urinary stones.
Typically, these are sterile struvite stones caused by the factors described. A bacterial infection as a trigger for struvite stones in cats is actually quite rare — but it does occur.
Symptoms Are Not Always Clear
Distinguishing between struvite stones, other urinary stones, and general urinary tract diseases based on symptoms is hardly possible. However, there are signs that owners should watch for and discuss with a veterinarian. Typical symptoms of a urinary tract disease include:
- Frequent urination in small amounts
- Pain and burning during urination, noticeable through whining or crying
- Incontinence, such as urinating outside the litter box
- Blood in the urine
- Excessive licking in the genital area
If these symptoms occur, a visit to the veterinarian is necessary. Typical symptoms initially affect urination difficulty — if urination stops completely, it is an emergency.
Bladder stones can not only cause pain but also lead to permanent kidney damage if urine flow is obstructed. A complete blockage of the urethra is a life-threatening emergency. In general, male cats are considered more at risk because their urethra is narrower and longer than that of females.
Diagnosis
Struvite stones occur relatively frequently in cats and can have acute or chronic courses. In the worst case, they develop into a life-threatening situation. For diagnosis, a urine sample is first examined. The stones preferably form in alkaline urine with a pH value above 7.2. Typical are square, coffin-lid-shaped crystals, which alone do not allow a definitive diagnosis.
A sterile urine sample, obtained through bladder puncture (cystocentesis), allows for even more precise results. Additionally, X-rays or an ultrasound provide information about the size and location of the stones, which often have a characteristic star or pyramid shape in the body.
Struvite stones are generally not contagious — but can be in rare cases of bacterial inflammation. For infectious variants, the veterinarian prescribes antibiotics.
Treatment Options for Struvite Stones
In most cases, the sterile form is present, where a special diet is the focus. The food is adjusted to reduce protein, phosphorus, and magnesium while acidifying the urine. Many pet food manufacturers offer special diets for cats with urinary stone problems. The selection should be made in consultation with the veterinarian.
If the cat refuses the diet food, special medications can also help dissolve the stones and prevent new formation. The dosage must be regularly checked through urine tests. Additionally, increased fluid intake should promote excretion. If no improvement is seen, medication treatment is necessary.
If large stones are detected during diagnosis that can block the ureters, surgical intervention may be necessary. The abdominal cavity is opened, and the stones are directly removed from the bladder. Alternatively, attempts can be made to crush the stones and then flush them out. Even after such an intervention, diet food or medication is still needed to prevent recurrence. Urine samples should be regularly monitored — often it is sufficient to submit the urine at the practice.
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Prognosis and Prevention of Struvite Stones in Cats
Sterile struvite stones usually dissolve within two to four weeks with proper treatment. Infectious struvite stones may require longer treatment. Diet or antibiotic therapy should continue for about four weeks after the stones disappear. The more a cat drinks, the better minerals are diluted in the urine — even long-term.
The chances of recovery are good if struvite stones are detected and treated early. Timely therapy allows the cat to live a long and trouble-free life. The costs vary depending on the type of treatment. Diet changes and medications incur regular monthly expenses. To avoid struvite stones, a low magnesium content in food is important.
Switching from dry to wet food can also increase fluid intake. If unsure about the right food choice, consulting with a veterinarian can help. Multiple water sources or a drinking fountain further encourage cats to drink. Milk should not be part of the regular diet — a few drops of fish oil or homemade (salt-free!) chicken broth can make the drinking water more appealing to cats.
If surgical removal of urinary stones, including anesthesia, is necessary, the surgery costs can amount to about 600 euros. However, if kidney damage occurs due to urine retention, the prognosis worsens. Damaged kidneys cannot regenerate, so lifelong medication and special food may be required — with proper care, life expectancy remains high. 2