Hi and thanks for the query.
The detection of the calculus and debris is not based on just a scan alone but a variety of tests are done and then all the results are summed up and a conclusion is made.
An ultrasound scan has a 93 percent sensitivity and a CT scan has 91 percent sensitivity.
However, considering the cost and radiation exposure the ultrasound remains first choice. Having said that, some times debris and stones smaller than 0.5 mm can be missed on ultrasound scans but that does not mean the urologist will rule the possibility out. But the urinalysis and blood tests will also give some insight. So, all these tests and clinical signs are taken in to consideration and not just the scan results. Of course, if the scan shows a stone, then the diagnosis is confirmed.
Yes, if you pass a stone, you will definitely feel it and because the experience is painful.
If you pass a stone, the pain should last only a couple of days if you are on pain killers.
Let me know if you have further questions.
Please do not forget to leave a positive rating for the service by clicking on stars on top right corner.
Wish you good health.