The pain from kidney stones usually starts suddenly on either side of the lower back. It is totally excruciating and frightening. Before contacting help, drink gallons and gallons of water, and try to keep upright. Sometimes the stone will pass on, but then can cause severe pain if caught within the bladder. Then you want to pee every 2 minutes. With luck you will pass the little sod!
Otherwise you could have a lithotripsy (sp) when under anaesthetic your stone is hopefully blasted into a powder. This does not always work, and may need further treatment.
It is not at all life-threatening, just unbearably painful. I have had 5 in the last 25 years, after the 1st one, the pain is instantly recognised, so no need to panic, just scream!!! Occurs without any warning, unfortunately, last one I had was when having breakfast at Sao Paulo airport (Brazil) before a flight to London. Drank gallons of water and took pain-killers and I was fine. Eventually passed the tiny sod two weeks after getting home and opened a bottle of bubbly! Now have xrays every year, so far, so good.