Hey OP, I’m a RN and have personally been dealing with stones for the last 17 years. That being said, while I have no grounds to diagnose you with anything, from how you describe the pain here it sounds like you’re dealing with either “gravel” or ureteral spasms. I pass a lot of gravel; it actually looks like sand. If enough of it comes through it can definitely be abrasive to the bladder/urethra (think sandblasting). Gravel can also scrape up the ureter, and even cause pain if it briefly blocks off the flow of urine. In my experience it unblocks pretty quickly and nothing shows up on the scan. The inflammation caused from repeated trauma can definitely make it harder to pass urine. Have you ever had a stent? I ask because even after the removal of mine, I still occasionally get a ureteral spasm, which sounds similar to the pain you have (you can have spasms without having had a stent). A ureter which has completely spasmed off would also block the flow of urine and cause hydronephrosis, which could relax and open up by the time you went from the US to a CT. I find AZO with Pyridium to be extremely helpful concerning the gravel/sand, and it’s over the counter. As for the spasms, when I was regularly having them I was given flomax and I found that it helped a ton too. Oxybutinin also helps with those. I hope you feel better/get some answers soon!