Stone dissolving diets are prescription diets for the prevention and treatment of struvite bladder stones (uroliths) in cats. The benefits of stone dissolving diets are that they are a non-invasive way to treat bladder stones. Diets can also prevent the formation of new struvite as well as calcium oxalate crystals.
What are bladder stones?
Bladder stones are rock-like formations that develop in the bladder of the cat due to super-concentration of the urine. The most common type of bladder stones in cats are struvite (magnesium ammonium phosphate); other types include calcium oxalate, ammonium urate, calcium-ammonium-phosphate, urate, cystine and compound (stones that contain different materials).
Bladder stones get their name after their mineral formation, and the veterinarian must identify which stone(s) for them to develop an appropriate treatment plan.
Symptoms of bladder stones
- Frequent urination which often produces only a few drops
- Difficulty urinating (dysuria)
- Crying in the litter tray
- Blood in the urine (hematuria)
- Urinating outside the litter box
- Genital licking
Male cats are at increased risk because of their narrow urethra. If a stone or crystal blocks the urethra, urine is unable to pass out of the body (urinary obstruction) which causes a build-up of toxins in the blood.
How do bladder stones form?
The most accepted theory as to how bladder stones form is the precipitation-crystallisation theory. This means that urine becomes supersaturated with certain minerals, which can be due to diet, disease or infection — the excess precipitates into crystals which irritate the lining of the bladder which leads to increased mucus production. Crystals and mucus clump together and harden to form bladder stones.
How do stone dissolving diets work?
Stone dissolving diets are low in phosphorous and magnesium, promote acidic urine with a pH range of 6.0 to 6.5 which aids in dissolving stones back into the urine. acidic urine with a pH range of 6.0 to 6.5. The median dissolution time for cats is between 13-27 days.
Diets not only dissolve struvite crystals but may also prevent the formation of may decrease the risk of recurrence of struvite and calcium oxalate cystoliths.
Who makes stone dissolving diets?
- Hills s/d
- Royal Canin Veterinary Diet Feline Urinary S/O
- PURINA® PRO PLAN® VETERINARY DIETS Feline UR ST/OX
Unless your veterinarian instructs you otherwise, cats eat the diet exclusively. Other foods, treats and supplements can reduce the effectiveness of these diets.
A cat on a stone dissolving diet will need a follow-up appointment 3-4 weeks after commencing the diet to check the stones are dissolving.
Diagnostic workup will include a urinalysis to look for the presence of stones and measure urine pH as well as an x-ray or ultrasound to look for stones in the bladder.
If the stone does not seem to be dissolving after a reasonable time, it may require surgical removal.
Other ways to help
Increase water consumption:
Encourage water consumption to bring the cat’s urine specific gravity to 1.030. Dilute urine helps keep minerals in solution instead of forming crystals and stones. Ways to increase water consumption include switching to a wet stone dissolving diet that has higher water content, and ensuring the cat has access to fresh drinking water. Some cats can be encouraged to drink more by providing them with a water fountain bowl.
Provide at least one water bowl on every story of the house and bowls should be emptied and washed daily.
Encourage frequent litter box use:
Provide enough trays; one per cat, plus one extra. Remove solids twice a day and clean and replace them with fresh litter at least once a week.
What is the treatment for other types of stones?
Calcium oxalate and other stones which cannot be dissolved will need to be surgery to remove the stones from the bladder, which is known as a cystotomy.