Bladder stones, or "uroliths," are naturally occurring minerals that clump together to form tiny crystals. Uroliths can develop in the bladder, kidney, ureter, or urethra. They can be large or small and develop individually or in groups that can pass spontaneously into the urethra or obstruct the lower urinary tract. Once formed, stones will gradually increase in size and can be a serious and painful condition.
There are several types of bladder stones, including struvites, which are composed of magnesium, ammonium, and phosphate. Other stones are made up of any one, or combination of compounds, including calcium, oxalate, calcium phosphate, crystine, and ammonium urate.
Researchers don’t completely understand what causes bladder stones, but suspect it may be related to the urinary tract environment, diet, digestion, medication, genetics, and the amount and frequency of urination. If symptoms are not present, a vet may detect bladder stones by pressing on the abdomen or conducting a rectal exam.
Cats have highly concentrated urine that makes them particularly susceptible to bladder stones, especially when certain minerals or other substances are abundant. This may be caused by diet, inflammation, infection, or elevated pH levels in the urine.
A cat with bladder stones may exhibit no symptoms or may have any, or all, of the following:
- increased/frequent urination
- painful urination
- burning during urination
- excessive licking of genitals
- blood in urine
Dietary changes may help prevent struvite bladder stones, but it is imperative you speak to your veterinarian before making any changes to your cat's diet. Diets for cats with struvite stones contain reduced amounts of high-quality proteins to reduce urea in the urine, and reduced levels of phosphorus and magnesium to reduce the concentration of these minerals in alkaline urine. The addition of extra salt in the diet may increase urination, which will reduce the number of crystals and the length of time they remain in the bladder.