My ureter stone was detected by kub xray, ultrsound and ct. i drunk 4l water per day for 12days then kub xray result was normal. how it could be?

Likely passed stone: If the stone was wedged in the ureter, you would have likely had symptoms of pain on that side. Drinking lots of water would increase urine flow and possibly pushed the stone into the bladder and possibly even passed the stone when you urinated. Nevertheless, you should see a urologist to see what you should do to reduce the risk of stone formation, including hydration or possibly medication.