doctor's orders: treating and preventing kidney stones

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staying hydrated in the most important thing to help prevent kidney stones, according to kidney specialist dr. norman muirhead.

by karen hawthorne

published may 17, 2023

last updated feb 20, 2025

7 minute read

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7 minute read

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if you have had an episode of kidney stones, drinking one-and-a-half to two litres of water intake a day will help to prevent another one. getty

kidney stones are not actually stones. they actually develop when chemicals in your urine form a tiny crystal that grows into a mass the size of a grain of sand or as large as a golf ball, according to the kidney foundation of canada. very small stones can pass through your urinary system painlessly in urine. but if it’s larger or gets stuck, you may experience severe pain and possible bleeding.

kidney stones are common in canada, with about 12 per cent of men and six per cent of women developing a kidney stone at some point in their life. once you’ve had a kidney stone, you have a higher risk of developing another.

healthing spoke with dr. norman muirhead, a kidney specialist, professor emeritus of medicine at western university, and president of the ontario branch board of the kidney foundation of canada about kidney stones, who is at risk and how they are treated. muirhead, who was also a staff nephrologist at london health sciences centre university hospital in london, ont. from 1983 to 2020, offers one tip to avoid kidney stones: stay hydrated.

what are kidney stones?

dr. muirhead: kidney stones form in the kidneys themselves and are very common. they’re mainly calcium, with the vast majority composed of calcium oxalate. some of them have other calcium salts in them. for example, there’s a crystal called calcium hydroxyapatite, and then some of them are made of other things like uric acid, but those are much less common.

they’re often associated with certain things in the diet that can provoke the development of kidney stones or having a low urine output. most of us are at risk of developing a crystal formation in the kidneys that can form the basis of a stone — particularly if we’re not keeping our fluid intake up. fluid helps dilute the urine so the risk of those crystals forming is diminished.

what are the signs of kidney stones?

dr. m.: a lot of the times kidney stones can be present in the kidneys with no symptoms at all. i happen to know that i have two stones in my kidneys, but they’re not moving anywhere or going anywhere, so they don’t cause any symptoms.

stones that break loose or start moving around can get into the ureter, which is the tube leading from the kidney toward the bladder. when that happens, you develop pain. so the most important symptom is what’s called renal colic, which is the pain that comes from the ureter, leading from the kidney to the bladder trying to propel the stone out. this can be associated with bleeding as well. pain associated with red blood in the urine is almost always related to kidney stones because these stones are not smooth. they’re not like little pebbles that you might pick up in the bed of a river. these are jagged little rough things that can damage the lining of the urinary tract and can cause bleeding. so, pain and bleeding would be the two most important symptoms that you would have.

occasionally, kidney stones can block the flow of urine completely, and then you would wind up getting pain in the flank in the area where the kidneys are located and down toward the groin. if it’s associated with infection in the urine, you can develop a high fever and other symptoms associated with the infection. this can happen particularly in people who’ve had urological surgery and treatment for kidney stones in the past who are more at risk of infections.

how do people develop kidney stones? what are the risk factors?

dr. m.: urine is an interesting material. it’s what’s called a supersaturated solution, meaning there are things in the urine that would normally coalesce into crystals and precipitate out if it weren’t for other things in the urine preventing that from happening. we have calcium and phosphate in our urine under normal circumstances, but the amounts that are there would crystallize if it weren’t for other anti-aggregate materials in the urine. it doesn’t take much of an alteration in the composition of the urine for these to form. it can happen if we just have a reduced urine output or a reduced urine flow, we suddenly can precipitate that kind of crystallization. then there are some people who are predisposed to forming crystals where they have genetic abnormalities in the way they handle these substances in the kidney. we’re understanding more and more about what those genetic predispositions are all the time.

we certainly see kidney stones more often in individuals in their 40s and 50s, at least in part because kidney function tends to decline a little bit with age, along with the ability to produce all of the things that prevent crystals. that doesn’t mean that we don’t see kidney stones in young people. but when we see kidney stones, usually in very young people, it’s the result of some underlying abnormality in the way they handle these substances.

are there lifestyle choices that can help prevent or treat kidney stones?

dr. m.: in terms of prevention, there are strategies that we use for people who’ve got established stone disease to reduce the likelihood of recurrence. those are lifestyle things like the increase in fluid intake and then modifications to the diet that may be appropriate. but it would be unreasonable to subject people who haven’t had kidney stones to the dietary restrictions and recommended fluid intake.

one of the key management strategies for patients who have kidney stones is to encourage them to drink a couple of litres of water, so that’s eight cups of water daily to help dilute the urine a bit. my patients used to complain to me that if they drank that much, they’d be up at night peeing, and i said, ‘that’s fine. so when you’re up, just drink a glass of water.’

modification of tea and coffee intake is one of the things that we recommend, and limiting foods high in oxalate, like dark chocolate, strawberries and rhubarb. there’s some evidence that a modest reduction in protein intake can be helpful as well. people who’ve got recurrent stones would usually see a dietitian to look at their diet and then have appropriate modifications suggested.

how are kidney stones generally treated?

dr. m.: sometimes people do expel the stones, so you will see the stones appearing in the urine. we often ask people who’ve had this episode of renal colic to strain their urine and collect the stone, and then you can analyze the stone and figure out what it’s made from. that’s a useful way of guiding treatment, because depending on the composition of the stone, you can figure out whether you need modifications to diet.

most of the time what will happen is if the stone is small, it will pass spontaneously within a few days. at that point, it’s just a question of controlling the pain until the stone is passed and making sure the patient has no further stones. about 90 per cent of stones will be seen on an x-ray, so we can see whether any additional stones are present within the kidney and their size. for the first episode, that’s really all that’s required. if someone has a big stone that they’re not going to pass by themselves, they’ll have a procedure called lithotripsy, which is an ultrasound method for breaking the stone up into smaller fragments that get passed through the bladder into the urine.

what’s interesting is that people can go through successive waves of stones. so they’ll form them for a few months or a year or two, and then they’ll stop producing stones, and then it’ll be another 10 years before they develop them again. having recurrent episodes is not uncommon.

what’s one piece of advice for someone with kidney stones?

dr. m.: the single most important piece of advice i would give people is to keep your water intake up. that’s really going to be the thing that will reduce the frequency of further attacks. diet modification and even drug treatment is going have an impact to some degree, but you’ll get a significant reduction in the likelihood of future stone episodes just by maintaining one-and-a-half to two litres of water intake a day. most of us find that hard to do, to be honest with you, i have a big water bottle sitting in front of me that i’m supposed to be drinking from and i haven’t taken a sip from it yet.

for more information about kidney stones, visit the kidney foundation.

karen hawthorne is a toronto-based writer.

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karen hawthorne

karen hawthorne worked for six years as a digital editor for the national post, contributing articles on health, business, culture and travel for affiliated newspapers across canada. she now writes from her home office in toronto and takes breaks to bounce with her son on the backyard trampoline and walk bingo, her bull terrier.

doctor's orders: treating and preventing kidney stones