Hyperuricosuria & Hyperuricemia (HUU) in the Biewer Terrier*

Educational Information for Biewer Terrier Owners

What is HUU?

Hyperuricosuria and Hyperuricemia (HUU) is an inherited disorder of uric acid metabolism caused by a mutation in the SLC2A9 gene. Affected dogs cannot efficiently convert uric acid to allantoin, allowing uric acid to accumulate and increasing the risk of painful urate stones in the bladder or kidneys.

HUU is inherited as an autosomal recessive trait. Dogs with two copies of the mutation are at risk of developing the disease, while dogs with one copy are healthy carriers that can pass the mutation to their offspring.

Clinical Signs

Affected dogs often develop signs between 1 and 6 years of age. Symptoms may include:

  • Frequent or difficult urination
  • Straining to urinate
  • Blood in the urine
  • Excessive licking of the genital area
  • Lethargy
  • Vomiting
  • Loss of appetite

A urinary blockage is a life-threatening emergency requiring immediate veterinary care. Males are at greater risk because of their anatomical structure.

Diagnosis

Your veterinarian may recommend:

  • Physical examination
  • Urinalysis and urine culture
  • Ultrasound or other advanced imaging
  • Stone analysis
  • DNA testing for the SLC2A9 mutation

Because urate stones are often not visible on standard X-rays, ultrasound and urine testing are commonly used for diagnosis.

 Treatment & Management

Treatment depends on whether stones are present and may include:

  • Prescription low-purine diet
  • Increased water intake
  • Medications such as allopurinol, when appropriate. This medication reduces uric acid production and helps decrease the risk of urate stone formation.
  • If a urinary stone causes an obstruction, emergency surgery (such a cystotomy or urethrostomy), may be required.

Lifelong dietary management and maintaining good hydration help reduce the risk of future stone formation.

Breeding Recommendation

When the Biewer Terrier was established as a distinct breed, there was limited breed-specific health information available to guide pre-breeding genetic testing recommendations. As a result, the health testing protocol used for the Yorkshire Terrier—the breed’s primary ancestral foundation—was initially adopted. Because Hyperuricosuria (HUU), caused by the SLC2A9 mutation, had been identified in Yorkshire Terriers, HUU testing was originally recommended for Biewer Terriers.

Since genetic testing became available, no laboratory has documented a confirmed carrier or affected Biewer Terrier with the HUU (SLC2A9) mutation. Based on this evidence, HUU testing was reclassified as an optional test for the breed in 2018 for OFA.  As of 2025, no confirmed carriers have been reported by laboratories testing Biewer Terriers, suggesting that the mutation is either absent or extremely rare within the breed’s current gene pool.

The BTCA Health & Research Committee supports optional HUU genetic testing, particularly for dogs with a family history of urinary tract stones or when clinically indicated.  If genetic testing suggests that a Biewer Terrier carries the HUU (SLC2A9) mutation, confirmation through a reference lab such as UC Davis or Cornell University is recommended before making breeding decisions. If carrier status is confirmed,  the BTCA Health & Research Committee recommends that the dog not be used for breeding in order to help prevent introduction or propagation of the mutation within the breed.

If a confirmed positive result is identified, the Committee encourages owners to report the finding to the BTCA Health & Research Committee so the information can be reviewed and, if appropriate, incorporated into ongoing breed health monitoring efforts.

Genetic testing is available through Embark, UC Davis Veterinary Genetics Laboratory, and Wisdom Panel.

Key Points

  • HUU is an inherited disorder of uric acid metabolism.
  • Dogs with two copies of the mutation have the greatest risk of developing urate stones.
  • Healthy carriers do not develop the disease but can pass the mutation to their offspring.
  • Difficulty urinating is a veterinary emergency.
  • DNA testing supports informed breeding dec

*This educational handout compiles public veterinary literature and does not represent original research, official policy, or guidance from the Biewer Terrier Club of America (BTCA). This information is for educational purposes only and is not a substitute for professional veterinary diagnosis, treatment, or medical advice. Owners of dogs showing new or unusual symptoms should consult a licensed veterinarian immediately. The BTCA Health Committee encourages members to consult qualified veterinary professionals for all canine health decisions.

Educational Resources & Further Information