Canine leishmaniosis is a life-threatening zoonotic disease with a wide distribution and allopurinol is a parasitostatic drug used in its long-term fashion treatment. Some retrospective reports indicate that xanthinuria deposits can appear secondary to prolonged therapy with allopurinol in dogs. The purpose of this prospective study was to evaluate the incidence, characteristics and the time of appearance of urinary adverse effects in dogs with leishmaniosis treated with allopurinol. Moreover, in dogs with xanthine deposits, clinical response to low purine diet was also evaluated.

This study included 20 dogs with a new diagnosis of leishmaniosis under allopurinol treatment (10 mg/kg/12 h during 12 months). Dogs were evaluated at time of diagnosis, one, six and twelve months after diagnosis and treatment with allopurinol, additionally 11/20 dogs were also evaluated at 3 months. Each clinical evaluation included the following tests (physical exam, abdominal ultrasound, UPC ratio, urinalysis, hematology, biochemical panel and Leishmania serology). All dogs had an unremarkable urinary ultrasound without urinary sediment before treatment. At one-month control, 4/20 dogs had xanthinuria, 2/20 mineralization of pelvic recesses (MPR) and 1/20 vesical urolithiasis. At three-month control, 4/11 had xanthinuria, 4/11 bilateral MPR and 2/11 urolithiasis (located in renal pelvis and bladder in 1 dog and the other in bladder). At 6-month control, 4/20 dogs had xanthinuria, 6/20 bilateral MPR, and 4/20 urolithiasis (located in renal pelvis and bladder in 2 dogs and in renal pelvis in the other two). At 12-months control, 7/20 dogs had xanthinuria, 7/20 bilateral MPR, and 6/20 urolithiasis (located in bladder in 3 dogs and in renal pelvis in the other 3). Dogs that suffered from xanthinuria and renal mineralization or urolithiasis were treated with low purine diet. Reduction of xanthinuria and uroliths size was observed in 3 dogs with compliant owners and strict diet treatment, but MPR persisted.

In conclusion, the present study describes an elevated and prompt incidence of urinary adverse effects associated with allopurinol treatment. A closer followup including urinalysis and abdominal ultrasound is mandatory in dogs treated with allopurinol. Moreover, according to our results, low purine diet seems to be an option in reducing xanthine deposits. Further studies are required to evaluate the efficacy of dietary treatment. According to authors' knowledge, this is the first prospective study that confirms previous suspicion of urinary adverse effects of allopurinol treatment in dogs with leishmaniosis.

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