You don't always pass stones if the kidney(s) have them. In my case, I just woke up one morning and peed blood. I mean blood. No pain. Called my general Doc, they had me come in immediately, then immediately sent me to the urologist. Got passed through a machine (MRI?) and it turned out I had what's called a staghorn stone, which had pretty much filled one kidney. Took 4 procedures to be rid of it: 1st was invasive with tubes, rest were an ultrasound deal & a stent.