What causes renal colic pains at night?
CT scan might be the solution
The symptoms you have described are by no means conclusive of renal colic. Ultrasound is not confirmatory exam for stones though it is very good for for swelling of kidneys or stones in kidneys.
However before dismissing your symptoms as being from source outside the kidney, you could get a 64slice CT scan done of your KUB region which should pick even a small pathology in the region. A plain study would be good enough for excluding stones. However administration of IV contrast may give indication if function and swelling as well.
You can also get a basic workup which should include a urinalysis, serum creatinine, complete blood picture, an X-ray if KUB region and we can take it from there.
You might also get an evaluation for bladder outlet obstruction since you gave relief after voiding urine and might get benefit from use of drugs like flomax
Hope I have been of help.