What Causes Crystals in a Cat's Urine?
- Cats with urolithiasis avoid the litter box.
Cat owners who keep their cats' shots up to date and feed them a balanced diet are often puzzled when their feline friends are diagnosed with "crystals" in their urine. A 2007 study at the Minnesota Urolith Center, College of Veterinary Medicine, University of Minnesota defined the condition created by these crystals as urolithiasis: an "occurrence of familial, congenital, or acquired pathophysiologic factors that, in combination, progressively increase the risk of precipitation of excretory metabolites in urine to form stones (uroliths)." The uroliths are crystals that consist of minerals---magnesium ammonium phosphate (struvite) or calcium oxide---and can block the urethra, resulting in a painful condition that used to be called Feline Urinary Syndrome (FUS) and was frequently fatal. Today, this serious condition is called Feline Lower Urinary Tract Disease. Although the causes of FLUTD are still not completely understood, after nearly three decades of study, veterinarians know more about how to manage the production of the crystals and to detect the major symptoms. - Too many animals can cause stress.
Struvite, at one time the most common type of uric crystal, was most prevalent in neutered cats that ate diets rich in protein, high in ash and low in pH. Through experimentation, veterinarians found that they could reduce the formation of struvite by feeding food with a higher pH (more acidic), less protein (lower in magnesium) and less ash content (lower in phosphates). Other contributing causes of urolithiasis, or crystal formation, were also identified; stress caused by changes in the household such as moving, number of animals, genetic predispositions or liver disease. Neutered cats, with their narrower urethras, appeared to be more susceptible to blockage. - Young females are more likely to develop struvite crystals.
As veterinary science learned more about FUS in the 1980s, pet foods were developed to address the causes of urolithiasis that could be identified and managed. As the pH levels were elevated and magnesium levels were lowered in pet foods, though, sick cats began to appear with less struvite and more calcium oxide crystals in their urine. In a 1996 study at the Minnesota Urolith Center, College of Veterinary Medicine, University of Minnesota, middle-aged, neutered male cats and Burmese, Persian and Himalayan breeds were identified as more likely to develop calcium oxide crystals, pointing to some hereditary-, age- and gender-related causative factors. Calcium oxide crystals were also the predominant type of crystal found in the kidney. The study found, however, that young (1- to 2-year-old) females were more likely to develop the struvite-type crystals. Although this research may be of little comfort to a cat owner who has lost a cat to FLUTD, it has provided ways to evaluate probabilities in diagnosis and clues to ways to modify foods and environments in disease management.
