Hyperuricosuria (HUU) in Dogs: Causes, Testing & Care

Hyperuricosuria (HUU) is a hereditary canine condition where affected dogs excrete an abnormally high level of uric acid in their urine. This predisposes them to form painful kidney and bladder stones, as well as cystitis, which can seriously affect quality of life.

The root cause is a gene mutation that disrupts the normal transport of uric acid between the liver and the kidneys, leading to its accumulation in the urine. As a result, crystals form and eventually develop into stones that can block urinary passages.

These stones can be extremely painful and often cannot be naturally passed, necessitating surgical removal. Managing HUU includes feeding prescription diets to reduce urine acidity, helping lower the risk of stone formation. However, long-term care can be challenging and treatment costs may be significant.

HUU is a genetic condition, passed by inheritance and is not contagious. Dogs must inherit two mutated gene copies (one from each parent) to be affected. Carriers carry one copy without symptoms but can pass the mutation on.

To help prevent the spread of HUU, The Kennel Club runs a testing scheme for breeds at risk, enabling breeders to check their dogs’ status before breeding.

This guide explains hyperuricosuria in dogs in detail, covering susceptible breeds, genetic inheritance patterns, testing procedures, and effective management techniques.

Understanding Hyperuricosuria in Dogs

The key effect of HUU is a tendency for urine to become overly acidic, encouraging the formation of uric acid crystals. These crystals aggregate into stones that cause urinary tract blockages and painful urination episodes.

If stones block the urinary tract, emergency veterinary care is essential to relieve obstruction and prevent life-threatening complications.

While surgical removal of stones is common, it does not cure the underlying condition. Prevention through careful diet and regular veterinary monitoring is crucial to reduce recurrence risks.

Which Dog Breeds Are Affected?

Hyperuricosuria can theoretically occur in any dog breed registered in the UK, but the breeds most at risk and recommended for genetic screening by The Kennel Club include:

• Dalmatian puppies
• American Bulldog puppies
• French Bulldog puppies
• English Bulldog puppies
• Large Munsterlander puppies
• Russian Black Terrier puppies

Crossbreeds can inherit the condition if both parents carry the gene mutation, though hybrid vigour may reduce incidence odds. Regardless, awareness is important for all dog owners and breeders.

How Is Hyperuricosuria Inherited?

HUU follows an autosomal recessive inheritance pattern, meaning:

• Two copies of the mutated gene cause the dog to be affected and show clinical signs.
• One copy makes a dog a carrier who does not show symptoms but can pass it on.
• No copies mean the dog is clear of the mutation.

The genetic combinations in breeding pairs determine the puppies’ risk:

• Two clear dogs produce clear puppies.
• Two affected dogs produce affected puppies.
• Two carriers produce 25% affected, 50% carriers, 25% clear puppies.
• One clear and one carrier produce 50% clear and 50% carriers.
• One clear and one affected produce 100% carriers.
• One carrier and one affected produce 50% affected and 50% carriers.

Testing Your Dog for HUU

The Kennel Club maintains a list of UK-approved laboratories for genetic testing of hyperuricosuria. Testing involves:

1. Requesting your vet to collect a DNA sample, typically via blood or cheek swab.
2. Sending the sample to an approved lab for analysis.
3. Receiving results indicating your dog’s status as clear, carrier, or affected.

This information is recorded by The Kennel Club and helps breeders make informed mating decisions to avoid producing affected puppies.

Managing and Preventing HUU

Management focuses on reducing uric acid levels and preventing stone formation through:

• Dietary control: Prescription diets formulated to lower urine acidity and uric acid concentration.
• Regular veterinary monitoring: Early detection of stones before they cause severe problems.
• Prompt veterinary treatment of urinary issues, with surgery reserved for removing obstructive stones.

Breeding strategies are vital to reduce HUU’s prevalence by avoiding mating two carriers or affected dogs. Responsible breeders use DNA testing to guide pairings, promoting healthier future generations.

Why Is Responsible Breeding Important?

Since hyperuricosuria is inherited, responsible breeding practices play a crucial role in reducing its incidence. Avoiding breeding dogs affected by or carrying the HUU mutation helps protect the overall health of breeds prone to this condition.

Using The Kennel Club’s health testing schemes and only breeding dogs with clear genetic status is the best way to safeguard puppies’ health and wellbeing.

Summary

Hyperuricosuria (HUU) is a painful genetic disorder leading to excess uric acid in dog urine, causing painful urinary stones requiring possible surgery. It primarily affects breeds like Dalmatians, French Bulldogs, and American Bulldogs. Understanding inheritance patterns, testing your dog’s genetic status, and managing the condition through diet and veterinary care are key to living well with HUU. Responsible breeding efforts are essential to reduce the impact of this condition for future canine generations.