Hello, if no tumor or stone could be identified in the kidneys then your bladder and prostate should be investigated. The best test for your bladder is cystoscopy which involves direct visualization of the bladder. The prostate can be examined clinically, radiologically and by biopsy (depending on clinical and radiological information). Tumors may cause intermittent bleeding, so they have to be excluded. You haven t mentioned any symptoms so urinary tract infections and glomerulary diseases are probably out of the question also. So in conclusion, any case of urinary tract bleeding requires investigation for tumors, unless the bleeding can be satisfactorily explained. You can contact me again, if you d like, for any further questions you may have. Kind Regards!