What is Xanthinuria?
Xanthinuria simply means an excess of xanthine in the urine. Xanthine is a by-product of the metabolism of certain proteins. It is normally found in the muscles, liver, spleen, pancreas and urine and is broken down and degraded to uric acid by enzymes. With hereditary xanthinuria, however, there is a deficiency in either xanthine dehydrogenase/oxidase (XDH/XO, type I xanthinuria) or molybdenum cofactor sulfarase (MOCOS, type II xanthinuria) that can retard or prevent this necessary conversion from taking place. As a result, xanthine can accumulate in blood and urine and can cause urinary stones (bladder and/or kidney) and kidney failure.
Type I and II xanthinuria result in the same clinical signs. The primary organs affected are the urinary tract and, in rare occasions, skeletal muscles and joints. Xanthinuria leads to the development of urinary stones (uroliths) in the kidney or bladder. These stones can cause irritation that can manifest as straining to urinate, frequent urination, urgency with urination, blood in the urine, or life-threatening urinary obstructions. Microscopic crystals can also accumulate in the kidney and cause kidney failure. Xanthinuria is exceptionally rare and most reports estimate that less than 1% of all kidney stones found in dogs are xanthine stones.
Patients with xanthinuria can present at virtually any age from a few months onward. One case in TMTs was diagnosed at just 8 weeks, another at almost a year, however research into the disease in Cavalier King Charles Spaniels and Dachshunds indicates average age of onset to be 6-7 years. Presentation is usually with xanthine stones, xanthine crystals in the urine or kidney failure. Unrecognised, any of these can lead to end-stage renal disease and even death. Though serious consequences can occur, at least 50% of humans with xanthinuria have been found to remain asymptomatic throughout life, a fact mirrored in Dr. Furrow's research with the identification of an adult female carrying two copies of the affected gene but who remains symptom free. Generally, males appear to be more likely to form stones than females and in humans only approximately 1/3 include stone formation among their symptoms.
Once diagnosed, patients with stones can be treated surgically, but the disease tends to recur without additional intervention. High fluid intake is key, along with a low purine diet. Prescription low purine diets are available, such as Science Diet Prescription Diet u/d and i/d Sensitive and Royal Canin Veterinary Diet Urinary UC Low Purine. Egg, nuts, and dairy are generally low purine sources of protein; foods with high purine content such as liver, kidney, bacon, and most seafood should be avoided.
Type I and II xanthinuria result in the same clinical signs. The primary organs affected are the urinary tract and, in rare occasions, skeletal muscles and joints. Xanthinuria leads to the development of urinary stones (uroliths) in the kidney or bladder. These stones can cause irritation that can manifest as straining to urinate, frequent urination, urgency with urination, blood in the urine, or life-threatening urinary obstructions. Microscopic crystals can also accumulate in the kidney and cause kidney failure. Xanthinuria is exceptionally rare and most reports estimate that less than 1% of all kidney stones found in dogs are xanthine stones.
Patients with xanthinuria can present at virtually any age from a few months onward. One case in TMTs was diagnosed at just 8 weeks, another at almost a year, however research into the disease in Cavalier King Charles Spaniels and Dachshunds indicates average age of onset to be 6-7 years. Presentation is usually with xanthine stones, xanthine crystals in the urine or kidney failure. Unrecognised, any of these can lead to end-stage renal disease and even death. Though serious consequences can occur, at least 50% of humans with xanthinuria have been found to remain asymptomatic throughout life, a fact mirrored in Dr. Furrow's research with the identification of an adult female carrying two copies of the affected gene but who remains symptom free. Generally, males appear to be more likely to form stones than females and in humans only approximately 1/3 include stone formation among their symptoms.
Once diagnosed, patients with stones can be treated surgically, but the disease tends to recur without additional intervention. High fluid intake is key, along with a low purine diet. Prescription low purine diets are available, such as Science Diet Prescription Diet u/d and i/d Sensitive and Royal Canin Veterinary Diet Urinary UC Low Purine. Egg, nuts, and dairy are generally low purine sources of protein; foods with high purine content such as liver, kidney, bacon, and most seafood should be avoided.