Autosomal Recessive

What is Canine Hyperuricosuria?

Canine Hyperuricosuria is higher than normal levels of uric acid in the urine in dogs. This high concentration of uric acid leads to the formation of stones in the bladder (or sometimes kidneys) of dogs affected by the condition. These stones cause pain and inflammation as they move about in the bladder and urinary tract. If the hard stones are large enough, the dog may require surgery to have them removed.

What is the genetic component of Canine Hyperuricosuria?

Canine Hyperuricosuria is inherited in a simple autosomal recessive pattern, meaning that the dog must inherit a defective copy of the gene from both parents to be affected. A mutation in exon 5 of the gene SLC2A9 has been found in dogs presenting with hyperuricosuria. The mutation causes the transport of uric acid to be inefficient, leading to higher than normal concentrations of uric acid in the bladder.

How severe is Canine Hyperuricosuria?

Canine Hyperuricosuria is considered to be of low-medium severity as the bladder stones can be removed via surgery and treated dog do not usually have a shorter life expectancy unless they block the urinary tract.

What are the symptoms of Canine Hyperuricosuria?

Dogs with Canine Hyperuricosuria are likely to first display the typical early signs such as having difficulty urinating (dysuria) and having an inflamed bladder (cystitis). The disease progresses to a more dangerous and painful condition when the stones travel down the urinary tract and damage the tract or worse, block the urinary tract. Blockages can cause severe pain, illness and even death if emergency treatment is not administered to the dog. The severity of the symptoms is totally dependent on the size, location and behaviour of the stones.

Diagnosis of Canine Hyperuricosuria

Dogs with Canine Hyperuricosuria are often diagnosed relatively early with symptoms such as cystitis and dysuria arousing the suspicion of bladder stones from veterinarians. An ultrasound will often be performed to see the stones and rule out infection as a culprit. Other tests such as blood and urine tests can be performed to search for other clues but a definitive diagnosis is often confirmed via a PCR based DNA test.

Treatment of Canine Hyperuricosuria

As Canine Hyperuricosuria is often an inherited condition, treatment is in the form of removing the stones from becoming a problem for the dog. The stones can be removed via surgery as well as by using sound waves (under ultrasonography) to break the stones into smaller pieces to allow them to pass through with the urine of the dog on their own.

Prognosis and prevention of Canine Hyperuricosuria

Treating a dog with Canine Hyperuricosuria requires the reduction and removal of the bladder stones that will continually form in the bladder and/or kidneys. Special diets that will reduce the frequency of the stones from forming can be purchased for dogs to minimise the number of stones forming. Ultimately though, the best form of treatment is prevention. DNA tests are available to test breeding dogs for this painful condition. As long as at least one parent is clear of the disease (has 2 normal copies of the gene), the offspring of the parents will not be affected.

Breeds affected by Canine Hyperuricosuria

Dogs of ANY breed could be affected by Canine Hyperuricosuria but the close breeding of related Dalmations in the past has led to the breed becoming fixed (all purebred Dalmations carry 2 mutated copies of the gene) for the disease. There has been some outcrossing of Dalmations in recent times in an attempt to remove the mutated gene from the Dalmation population of dogs involved with the outcrossing program.

References

Bannasch D et al (2008) Mutations in the SLC2A9 gene cause hyperuricosuria and hyperuricemia in the dog. PLoS Genet 4(11):e1000246
Karmi N, Safra N, Young A, Bannasch DL. Validation of a urine test and characterization of the putative genetic mutation for hyperuricosuria in Bulldogs and Black Russian Terriers. Am J Vet Res. 2010;71(8):909-142
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Karmi N et al (2010) Estimated frequency of the canine hyperuricosuria mutation in different dog breeds. J Vet Intern Med 24(6):1337-1342
McCue J et al (2009) Urate urolithiasis. Compend Contin Educ Vet 31(10):468-475
Safra N et al (2005) Exclusion of urate oxidase as a candidate gene for hyperuricosuria in the Dalmatian dog using an interbreed backcross. J Hered 96(7):750-754
Safra N et al (2006) Linkage analysis with an interbreed backcross maps Dalmatian hyperuricosuria to CFA03. Mamm Genome 17(4):340-345