2,8-dihydroxyadenine (DHA) Urolithiasis

2,8-DHA urolithiasis or APRTD is a rare condition that predisposes affected dogs to the formation of 2,8-DHA urinary stones. Median age at presentation is 4 years, but can be diagnosed as early as one year of age. Clinical signs of urolithiasis include hematuria, stranguria, pollakiuria, and blockage of the urinary tract. These stones can obstruct the renal pelvis, ureters, or urethra. Stones can be visualized by abdominal ultrasonography or contrast urography. Patients with urinary stones are more susceptible to urinary tract infections, so urinalysis is recommended. Blockage of the urinary tract is a life-threatening condition that requires immediate veterinary care. Limited evidence suggests the clinical signs are more common in males than in females.

This condition has been managed similarly to other urolithiases, with fluid therapy and removal of existing stones by surgical, mechanical, or medical dissolution. Long term preventive management may include xanthine dehydrogenase (XDH) inhibitors and a low purine diet. Dogs who are homozygous for the mutation but asymptomatic should still be placed on preventive therapy, based on human studies of the condition. Lifelong management of the disorder with diet and monitoring for signs of urinary tract infection or blockage should be emphasized to clients. Routine urinalysis may be used as a tool to monitor response to therapy and compliance.

There are many responsibilities to consider when breeding dogs. Regardless of test results it is important that your dog is in good general health and that you are in a position to care for the puppies if new responsible owners are not found. For first time or novice breeders, advice can be found at most kennel club websites.

This disease is believed to be autosomal recessive, meaning that two copies of the mutation are likely needed for disease signs to occur. A carrier dog with one copy of the urolithiasis mutation can be safely bred with a clear dog with no copies of the urolithiasis mutation. About half of the puppies will have one copy (carriers) and half will have no copies of the urolithiasis mutation. A dog with two copies of the urolithiasis mutation can likely be safely bred with a clear dog. The resulting puppies would all be carriers. Puppies in a litter which is expected to contain carriers should be tested prior to breeding. Matings between two carriers of the urolithiasis mutation should be avoided, as it could produce puppies with two copies of the disease mutation. Please note: It is possible that disease signs similar to the ones caused by the urolithiasis mutation could develop due to a different genetic or clinical cause.