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tvpjournal.com | September/October 2015 | TOday'S VeTerinary PracTice Feline STruViTe & calcium OxalaTe urOliThiaSiS Peer reviewed 15 of calcium oxalate uroliths. Cats fed low-sodium or low-potassium diets or diets formulated to maximize urine acidity are at increased risk. 2,6 In 1981, less than 10% of the feline uroliths analyzed at the Minnesota Urolith Center were calcium oxalate; in 2013, that percentage had increased to 41%. 3 Use of acidifying diets is thought to have played a role in this increase: diets that produce a urine pH between 6 and 6.2 are 3 times more likely to produce calcium oxalate uroliths when compared with acidifying diets designed to produce a urine pH between 6.5 and 6.9. 2 In addition, metabolic acidosis increases calcium mobilization from bone and contributes to hypercalciuria as well as decreased urinary citrate excretion. RISK FACTORS Struvite Uroliths • Age: Peak incidence of struvite uroliths in cats appears to be between 2 and 7 years of age. 1 • Sex: Female cats appear to have increased risk for struvite urolithiasis. 7-10 • Breed: Breeds reported to have decreased risk for struvite uroliths include Burmese, Persian, Himalayan, Rex, Abyssinian, Russian blue, Birman, and Siamese. 7,8 However, one study found Siamese cats to be at increased risk for struvite uroliths. 10 • Concurrent infection: Infection-associated struvite uroliths are more common in kittens and older female cats. Risk factors for UTI in cats include female sex, Persian breed, increasing age, decreasing body weight, chronic kidney disease (CKD), hyperthyroidism, and diabetes mellitus. 11 Calcium Oxalate Uroliths • Age: Older cats (8–12 years) are most commonly affected by calcium oxalate uroliths. • Sex: Male cats most commonly develop calcium oxalate uroliths. 7-10 • Breed: Male domestic short-haired, medium- haired, and long-haired cats appear to be 1.4 times more likely to develop a calcium oxalate urolith than a struvite urolith, while both male and female purebred cats (eg, Persian, Himalayan, Burmese, ragdoll cats) appear to be at risk. 9 • Concurrent conditions: While concurrent UTI appears to be rare in cats with calcium oxalate uroliths, many cats with CKD also have calcium oxalate nephroliths. Recurrence of calcium oxalate uroliths in cats is a potential problem. In a study of more than 2000 cats with calcium oxalate uroliths, 7% had a frst recurrence, 0.6% had a second recurrence, and 0.1% had a third recurrence. 12 These results underscore the need for medical protocols aimed at decreasing recurrence of calcium oxalate uroliths after urolith removal. FIGURE 1. Lateral radiograph of a 6-year-old spayed female domestic shorthair cat with multiple struvite cystoliths ( A); 80% struvite, 20% ammonium acid urate cystoliths were removed from this cat (B). (Scale, 1 division = 1 mm) B A