How accurate are xrays in finding kidney stones?

Very good: Imaging studies nowadays are very good and accurate at detecting kidney stones. They can tell us the size and location of most stones. The vast majority can easily be diagnosed with current imaging studies. There is a small chance that a very small stone (less than 2 or 3 mm) may be missed but overall the detection rate for most stones is very high.

Not very accurate: Abdominal xray are usually not very accurate as the first study for kidney stones. Some stones are not opaque enough to be seen on an xray alone. The kidneys are frequently obscured by bowel gas & stools on the xray and can't be visuallized well, particularly if the stones are small. Ct (better) or ultrasound are better. Xray can be then used for follow up once the stones have been located.