I had an ultra sound that showed 4 stones 2 in each kidney all small enough to pass, 3mm & 5mm. Later CT scan shows nothing. I did not find a stone while straining the urine. After CT scan (that night) I had excruciating pain in lower abdomen, that was 2 d

If the CT. was performed with a specific protocol to assess for kidney stones, it is probably more accurate than the ultrasound. Other entities in the kidneys can mimic small stones on ultrasound, such as blood vessels and small fat deposits.