Hyperuricosuria, almost always called HUU in breeder shorthand, is the third of the three big recessive conditions in the American Bulldog breed (alongside NCL and Ichthyosis). It is not fatal in the way NCL is, but it produces a lifetime of urinary problems that affect both the dog and the owner.
What HUU is
HUU stands for Hyperuricosuria, literally "high uric acid in the urine." The condition is autosomal recessive and is caused by a mutation in the SLC2A9 gene (encoding the GLUT9 transporter). The mutation prevents the kidneys from properly recycling uric acid, leading to abnormally high uric acid in the urine, which precipitates as urate crystals and stones in the bladder and urinary tract.
HUU is not unique to American Bulldogs. The same mutation occurs in Dalmatians (where it is nearly fixed in the breed), Black Russian Terriers, Bulldogs, and several other breeds. In American Bulldogs the carrier rate is significant enough that testing is essential.
Symptoms
Affected American Bulldogs may show:
- Frequent urination
- Straining to urinate
- Blood in the urine
- Recurrent urinary tract infections
- Visible urate crystals in urine
- In severe cases, urinary obstruction (a veterinary emergency)
Symptoms typically emerge in young adulthood (1-3 years). Male dogs are at higher risk of obstruction because of urethral anatomy.
Treatment and management
HUU is managed, not cured. The standard approach:
- Strict low-purine diet for life (purines convert to uric acid). Specific veterinary prescription diets exist.
- Plenty of water (dilutes urine, reduces crystallization)
- Frequent urination opportunities (do not let the dog hold urine)
- Regular urinalysis monitoring
- Allopurinol or other medication when stones are forming
- Surgical removal of stones when they obstruct or recur
The lifetime cost of managing an HUU-affected dog (prescription diet, vet monitoring, occasional surgery) is significantly higher than for an unaffected dog. Early identification through testing or symptom management makes a major difference to outcomes.
How testing works
The SLC2A9 mutation is identified by simple DNA testing. Embark, UC Davis VGL, and other labs offer it. Result categories: clear, carrier, affected.
Breeding rules
- Test every breeding dog.
- Clear-to-clear and clear-to-carrier pairings are acceptable. No affected puppies result.
- Carrier-to-carrier pairings produce 25% affected puppies. Never acceptable.
- Disclose results to buyers.
Rosebull's HUU protocol
Every Rosebull breeding dog runs the full Embark panel. HUU status is on file. Pairings ensure no Rosebull puppy can be HUU-affected. Test reports are shared with buyers on request.