Calcium oxalate crystals in Kitty's urinary tract and bladder usually result from a high level of acid in his urine. Eventually, these crystals clump together and become bladder stones. Not only are these stones painful, but they can block Kitty's urethra, a potentially fatal condition. Prevention is the best strategy.
Calcium Oxalate Crystals
A generation ago, struvite crystals and stones were commonly found in cats with urinary tract disease, with calcium oxalate stones and crystals relatively rare. Because struvite, or magnesium ammonium phosphate, crystals formed because of too much alkalinity in the feline diet, commercial pet food manufacturers began acidifying their products. Today, the struvite crystal is much less common in felines, but more acidic urine means formation of calcium oxalate crystals and stones. Unlike the struvite variety, these crystals and stones can't be dissolved through dietary changes.
The initial symptoms of cats suffering from bladder stones or obstruction are similar to other types of feline lower urinary tract disease. Kitty constantly goes in and out of the litter box, straining to pee. He might lick his genital area for pain relief. Trying unsuccessfully to pee can hurt so much he starts yowling. If he's not completely blocked, you might see blood in the litter box, or Kitty starts peeing all over the house.
Your vet needs to know what kind of stone is causing Kitty problems. That's not something that can be determined by an X-ray or ultrasound. Calcium oxalate crystals don't appear in the urine as frequently as struvite crystals, but a urinalysis detects high acid levels. Approximately one-third of cats with calcium oxalate crystals also have elevated blood levels of calcium.
If Kitty has crystals, not stones, your vet may prescribe a diet to reduce the amount of acid in the urine, to prevent stone formation. If Kitty already suffers from calcium oxalate stones, surgical removal is the primary treatment, especially in the male cat. Because they have wider urethras, female cats might be able to pass small stones or crystals, but even this is the exception. Female cats may have stones removed via cystoscopy, in which a long instrument enters the urethra to retrieve the small stone. If a larger stone is involved, your vet might break it up into smaller pieces by using a laser, then performing the cystoscopy. In some cases, your vet might be able to flush out small stones in the lower part of the urinary tract.
The right diet can go a long way in the prevention of calcium oxalate crystals and stones. Ask your vet for recommendations. Generally, feed Kitty wet, canned food rather than dry. Look for a high-fiber, low-protein food. Make sure he always has plenty of fresh, clean water available and add a pet fountain to entice him to drink more often.
- Cornell University College of Veterinary Medicine: Feline Lower Urinary Tract Disease
- VetInfo: Calcium Oxalate Crystals in Cats
- VetInfo: Calcium Oxalate Stones in Cats
- DVM360: Improving Management of Urolithiasis: Feline Calcium Oxalate Uroliths
- Mar Vista Vet: Feline Oxalate Bladder Stones
- Merck Veterinary Manual: Feline Urolithiasis and Feline Lower Urinary Tract Disease (FLUTD)
Jane Meggitt has been a writer for more than 20 years. In addition to reporting for a major newspaper chain, she has been published in "Horse News," "Suburban Classic," "Hoof Beats," "Equine Journal" and other publications. She has a Bachelor of Arts in English from New York University and an Associate of Arts from the American Academy of Dramatics Arts, New York City.