I've written about this previously, but it's often hard to explain to people what a 10 is on the "1-10" pain scale if they haven't been in that spot before. For women who have had children, they generally know what a 10 is, but for men it's a little harder. When I was a medical student on my psychiatry rotation, we had a patient calmly sitting there saying his pain level was at a 10 and our resident, who was an ex-military sniper with a large skull tattoo on his forearm and a crosshair through the eye, calmly leaned forward and asked, "so if I lit you on fire and ran you over with my truck, you could not be in more pain than you are now, correct?" The patient changed his answer.
Getting to the point, a kidney stone is about the close I can come to describing a 10/10 pain to people who haven't gone through childbirth. The fundamental issue is similar - your body is trying to move a big solid thing through an opening that was not really designed to accommodate it that easily and the pressure buildup which comes in waves is just unbearable. Anybody who has had ear pain when the plane is landing knows a little about this.
But why do we get kidney stones? It's becoming a pretty common problem, affecting about 1 in 12 people, and while still happening more in men, women have been making up the difference in the last few years too. There are different types of stones, but three-quarters are calcium based, usually calcium oxalate and a little less often calcium phosphate.
The problem is how much of those elements end up in the urine. Sometimes that correlates with how much you have in your blood and other times it's just how your kidneys are deciding what minerals stay in the blood stream and what gets moved to the urine. It's generally not a simple issue of "eat less of X and you'll have less stones." Ironically, people with calcium oxalate stones are usually encouraged to eat more calcium in their diet because it helps bind the oxalate in the gut, which keeps both from being absorbed.
The classic way you find out about a kidney stone is a sudden, waxing/waning pain often in the flank (just on one side), radiating down to the groin. Sometimes there is some blood in the urine and sometimes it's just trace amounts you can't see with the eye. Rarely, they can be severe enough to totally block things up and cause urine to collect around the kidney, which usually needs a temporary outlet tube put in through the back to help drain it.
So long as you have two kidneys (because it's rare to have simultaneous stones on both sides), most of the time the first steps are drinking plenty of water to keep trying to flush the system and pain medication to help out (if you don't have two kidneys, kidney stones can be an emergency because it's the only way out you have). Sometimes if they don't pass on their own, a urologist can either break them up with sound waves or else go in and retrieve them, depending on how big they are and where they are.
One wrinkle is if you incidentally find out you have kidney stones on an xray or CT scan. There's about a 30-50% chance of those causing symptoms when they have followed people for 5 years and not much to do about them until they do, so it's almost better not to know about it if you do have them. For comparison, people who have already had a symptomatic kidney stone have about a 50% chance of having another one over the next 5-10 years.
There are other types of stones that can form in your kidneys like uric acid stones (most common in people with gout), cystine (more common in people with genetic disorders), and struvite stones which are made of magnesium usually and very prone to getting severe infections.
All that is to say, one of the strongest risks for stone formation in people who are susceptible (and you don't know if that's you until it happens) is to avoid getting dehydrated. Why? If your water levels go down, the concentration of whatever is in that water goes up and that's when stones form. So it's another good argument for keeping yourself adequately hydrated, meaning that when you pee it looks mostly clear. Also, for people taking megadoses of Vitamin D, that stuff will give you kidney stones. Same goes for Vitamin C.
