Dalmatians do not efficiently convert uric acid (poorly soluble) to allantoin (very soluble) because of a defective uricase enzyme system which results in decreased hepatic conversion of uric acid to allantoin, and a renal membrane transport defect that results in reduced tubular reabsorption of filtered urate. As a consequence, all Dalmatians excrete high concentrations of uric acid as the end-product of purine metabolism in their urine (hyperuricosuria).

The genetic inborn error of metabolism in this breed was successfully corrected about 20 years ago in an experimental test breeding of a Dalmatian female and an English Pointer. With the approval of the American Kennel Club, the F1 generation offspring was back-crossed to Dalmatians thereby producing phenotypically indistinguishable Dalmatians that lacked the inborn error of their ancestry. This remarkable achievement would have permanently solved the uric acid defect for subsequent generations, except that the parent breed club denied approval for registering this new genotype and the project was abandoned.

Urate Concentrations:
Breeds other than Dalmatian excrete 50-60 mg urate in urine over 24 hrs., whereas Dalmatians excrete 200-1000 mg urate in urine over 24 hrs.
English bulldogs also excrete high concentrations of uric acid in urine and are thus prone to urate urolithiasis.

• All Dalmatians have hyperuricosuria, and most (70-80%) young Dalmatians have some degree of urate crystalluria. However, the prevalence of stone formation is quite low in the breed so that not all Dalmatians need to be on preventive therapy.
  
• Age—low risk in puppies; most commonly seen at ~3 years of age; reduced risk after ~6 years of age as less uric acid appears to be excreted.
  
• Gender—the assertion is that males are at greater risk than females, but not all experts agree. It may appear that way because males get urethral obstruction.
  
• Urine uric acid concentrations - young adult Dalmatians having numerous urate crystals on repeated urinalyses are likely at risk, as are dogs that excrete of more than ~550 mg urate/24 hrs.
  
• Previous stone formation - known stone formers are at increased risk.

• Surgical removal of stones.
  
• Medical Dissolution—
• Hill's u/d diet, or equivalent prescription formula diet, has very low protein (10-12% on dry matter basis), compared to renal failure diets which have 16-18% protein on a dry matter basis and maintenance diets which have ~22% protein. [Note that the nucleic acids in diets, rather than proteins per se are the source of purines.] The u/d diet is alkalinizing as it contains K+ citrate; urine pH on this diet is typically 7.5-8.0. The canned food or moistened dry food formula is more effective than feeding u/d as dry food. Canned u/d typically produces urine specific gravity of ~1.005-1.006, whereas u/d fed dry results in ~1.015-1.020.
  
• Allopurinol: xanthine oxidase inhibitor that blocks conversion of xanthine to uric acid. Dose is ~15mg/kg q 12 hr.
  
• Stones dissolve typically in 1-2 months, but can take up to 6 months.
  
• Efficacy is ì60%.