The hitchhiker's guide to feline xanthinuria

Feline xanthinuria is a rare autosomal recessive disorder of purine metabolism due to genetic mutations in the xanthine dehydrogenase (XDH) gene. It is characterised by excessive excretion and accumulation of xanthine in the urine, which can lead to the formation of xanthine uroliths. Xanthine uroliths may be present in both the upper and lower urinary tracts, causing clinical signs associated with renal disease and feline lower urinary tract disorders (FLUTDs). Hallmark diagnostic findings of xanthinuria are elevated xanthine and hypoxanthine, and reduced uric acid concentrations in serum and urine. Uroliths can be submitted for compositional analysis to confirm the presence of xanthine and definitive diagnosis for xanthinuria. Management involves dietary modification to purine-restricted diets and increased fluid intake. Commercially available renal diets are preferred over urinary diets because of their lower protein composition, and consulting a veterinary nutritionist is strongly recommended. Urinary alkalisation is not considered an effective method for the dissolution of xanthine uroliths owing to their poor solubility. Despite these interventions, recurrence of xanthine urolithiasis is possible. Given the limited treatment options and risk of recurrence, feline xanthinuria is a lifelong condition that requires ongoing management and monitoring to mitigate complications. This review will provide an overview of the current understanding of the pathophysiological, metabolic and genetic aspects of the disorder and discuss current diagnostic approaches, management strategies and clinical expectations of feline xanthinuria. Findings from this review highlight the need for greater recognition of feline xanthine urolithiasis as a cause of FLUTD, given current gaps in diagnostic methods and treatment options. A deeper understanding of the condition will help veterinarians accurately differentiate it from other causes of FLUTD and support further research aimed at improving the detection, prevention and management of xanthinuria.