I had one once. The most excruciating pain I’d ever had, and that includes having a heart attack several years previously. I went to the ER, the doc gave me some great drugs, and I basically fell asleep for 8 hours. I woke up, and eventually left. Never did feel the stone passing out; the doctor said that perhaps it broke up on its own.
As far as prevention, they told me to drink – a lot.
B”H I’ve not had a recurrence.