2,8-Dihydroxyadenine uroliths in a dog.

CASE DESCRIPTION: A 43-kg (95-lb) 4-year-old neutered male mixed-breed dog was evaluated because of a 2-day history of dysuria.

CLINICAL FINDINGS: Radiography and ultrasonography revealed hydronephrosis, hydroureter, and radiolucent, hyperechoic uroliths in the right kidney and ureter and the urinary bladder. Serum bile acids concentration was within the reference interval.

TREATMENT AND OUTCOME: The uroliths in the bladder and right ureter were surgically removed and submitted for analysis. They were initially identified as urate uroliths; however, results of further analysis indicated uroliths were composed of 2,8-dihydroxyadenine (2,8-DHA), and 2,8-DHA was identified in a urine sample of the dog. Allopurinol was prescribed for the dog, and a purine-restricted diet was recommended.

CLINICAL RELEVANCE: 2,8-DHA uroliths are extremely rare in humans and dogs. Such uroliths may be underdiagnosed in humans because of variability of clinical signs and difficulty in differentiating 2,8-DHA and urate uroliths and crystalluria. Uroliths composed of 2,8-DHA may be misdiagnosed as urate uroliths in dogs.