Reasons for getting stones when doing flush:
If we assume that Ultrasound examination was error-free, there are stil several reasons:
1. Most stones are inside liver and Ultrasound can't detect cholesterol stones inside liver.
2. Ultrasound can't detect small stones inside gallbladder, or sometimes very soft stones inside gallbladder.
As ultrasound examination is not 100% reliable, there are also other possible reasons:
1. Stones do exist inside gallbladder, but examination failed to detect them due to position of gallbladder, or if there is no bile inside gallbladder
BUT, most likely your pain is not caused by stones inside GB, it is caused by stones inside liver .. so go and do flush!
You have nothing to loose, except your symptoms!