A case of idiopathic renal hematuria was described in a 7.5-year-old Napolitan Mastil canine that was taken to the veterinary due its hematuria with several months of evolution. The blood and urine tests and the imagenealogy aids (X-rays and ecography), were not useful to indicate a diagnosis. Hence, an exploratory celiotomy was recommended and after chateterizing the ureters from the inside of the bladder it was established that the bleeding came from the right kidney which was extirpated along with its ureter. There were carried out exams of histopatology of the extirpated kidney, being nefrosis and a widespread degenerative process to bark level and renal marrow. The hematuria was not solved during the postoperatory process, possibly because it had bilateral origin, the patient died of another non related cause, and it was not possible to evaluate the left kidney.