Figure 3. Lateral radiograph of a 5-year-old, castrated English bulldog with multiple cystine uroliths in the kidneys, bladder, and urethra (arrow).
Dachshund, mastiff, Chihuahua, Welsh corgi, bullmastiff, Scottish deerhound, basset hound, Irish terrier, English bulldog, and Newfoundland breeds are predisposed to forming cystine uroliths. Owing to the greater popularity of these breeds in Europe than in the U.S., the prevalence of uroliths varies geographically (>30% in some European studies vs. 1%–3% in the U.S.). The mean age of dogs with cystine uroliths is 4-6 years. Male dogs (98%) are affected to a much greater degree than females (2%), and most cystine uroliths (98%) are found in the lower urinary tract (bladder and urethra). Newfoundlands appear to be an exception as cystine uroliths form in younger (<1 year of age) males and females and can also be found in the kidney. Maned wolves from South America have also been shown to have a high incidence of cystinuria and are predisposed to forming cystine uroliths.