How do kidney stones form?

(See a visual timeline of kidney stone formation below)

Kidney stones are formed from substances known as soluble salts. Calcium oxalate-the most common type of kidney stone, is a soluble salt. It can exist in a dissolved form or in a solid, crystalline form.

When the concentration of a soluble salt in solution is high enough, it will begin forming into solid crystals, in a process known as precipitation. An example of a common soluble salt is sodium chloride in seawater. When seawater is allowed to stand and evaporate, the previously dissolved sodium chloride precipitates out of solution in the form of sea-salt.

Urine contains many chemical elements that can also combine to form soluble salts. These chemicals normally remain in a dissolved form in urine. Surprisingly, the concentrations of these salts in urine are usually much higher than what could remain dissolved in pure water. This unusual situation can occur because of the presence of inhibitors in urine that make it more difficult for soluble salt crystals to develop.

Some kidney stone inhibitors are substances from our diet, such as citrate, while others inhibitors are proteins manufactured by our bodies to help prevent the development of stones. Two examples of inhibitor proteins made by our bodies include Tamm-Horsfall protein and nephrocalcin.

Kidney stones initially form in a process known as nucleation when the factors encouraging salt crystals to develop outweigh the factors inhibiting salt crystals to develop. These crystals will continue to get larger over time and result in a detectable kidney stone if the conditions in urine remain favorable for stone formation.

Other important factors that affect the development of kidney stones include the amount of urine a person makes, with lower volumes leading to more concentrated urine, and the presence of slowed drainage, which can make it easier for crystals to gather and combine. The presence of a binding site can also make it easier for stones to start forming by acting as an “anchor” for crystals to develop on. A natural binding site is thought to be the small calcifications that can develop in kidney tissue known as “Randall’s plaques”.

A visual timeline of kidney stone formation

Click on images to enlarge them.

 

Image of precursor of kidney stone formation

 

Early development of a kidney stone

 

 

Growth of a kidney stone

Detachment and start of a kidney stone episode

 

15 Responses to How do kidney stones form?

  1. sophia archer says:

    I had a UTI back in Nov ’13 and continued to feel milaise. PCP SENT me to urologist and they took tests, CT and ultrasound. Then I had a cystoscopy. Kept find blood in urine, but could not pin point nothing.this was end of May.beginning I my of July, find myself in ER, killed in pain…come to find kidney stones in both kidneys, multiples in the right, largest being 8mms and the other in my left is just over 1 cm. I now have stents. Good times…not bad at first, but seems be less accommodating to my body than when we first meant. Can’t wait for removal of stones,and then f I’ll nail departure of stents!

  2. Andrew says:

    I had a kidney stone back in 2008 (my first one) at age 23. I enjoy working out and was on a high protein diet, but i drank close to a gallon of water a day. Fast forward to 2014 and I am starting to notice lower back pain. its very light and i dont notice it very much, but i recall from my last one it starting out that way. I believe i am doing enough to prevent them by drinking a lot of water. I still stay very active and maintain a high protein diet, but I still drink a TON of water and don’t consume an abundance of sodium

    Am I in that wheelhouse of a recurring stone due to my bodies composition, or is high protein diet still the the reason my stone(s) may be forming. I do eat a lot of almonds and other nuts, as well as eat spinach, but i still drink a lot of water. My first experience I had two at once and my concern is that I will develop another one if I don’t change my diet.

    Should I discuss with my Dr. if I am prone to continuous stones? Or, is it just my diet that is the culprit?

    • Marcus Braga says:

      Hey, im in the same exact boat!!!! My first was at age of 23 in 09, now last week I had my second. I was wondering if you could share info on the diet part. I do eat alot of protein. Can u recomend anything to help dissolve and avoid them? Thank you so much!

  3. Sheryl Ferguson says:

    The worse part is having to wait so long to have them removed!

  4. Barbara says:

    I just had a kidney stone attack 6 days ago. My back had been hurting increasingly over 2 weeks & then at 3am that morning I woke up in horrible pain with nausea & vomiting. There’s an 8mm just outside the kidney & another 8mm about to drop out of the kidney. They placed a stent & scheduled surgery for one month away. Today the opposite side of my back is starting to hurt. I do not know if the CT was of both sides but think not since they confirmed about 100 times that it was my left side. Would that be improbable & weird to get stones in both kidneys at the same time. …the first time??

    • Sheryl Ferguson says:

      I had pain on both sides of my back and abdomen, but had 2 stones – one in the left kidney and one just outside the left kidney.

  5. Santosh Sushil says:

    A good and useful site.

  6. stewart mckenzie says:

    i get stones atleast once a year it starts with kidney pain and when i go to the toilet to wee the wee is so red from blood does it mean the stone is moving down and causing damage to the kidney ?

    • sulleh says:

      yes, very, check it out with a doctor.

      • Sheryl Ferguson says:

        I have blood in my urine with a bladder infection – without a kidney stone, so I don’t necessarily think it means your kidney is being damaged. However, if you are not treated for your stone, it can cause damage.

        • Pathology student says:

          My renal pathologist professor told us that if you ever see blood in your urine, always, always get it checked out! It could easily escalate into something more serious.

  7. Shehab says:

    This information is very helpful. Putting it in layman terms makes it so much easier for those of us who are not familiar with medical terms. Is there any tests to comply with on a monthly basis to ensure one does not suffer from stones ?

  8. Michelle says:

    I have been trying to manage the pain from a large kidney stone for more than 7 mos now. No insurance to do anything about it. Meanwhile I have been trying to learn about them and why and how and where they are in my kidney. I am haveing the sound wave surgery in a week. Although I have learned a lot about the kidneys and their functions, I have learned very little about the kidney stones and how they are formed. This article has taught me more than anything I have read so far. I now have a much better idea of how this happened to me and what I can do to help prevent it. The best thing is that I understand what is happening inside of me. I have adreanal mass inside my kidney, which I was like Huhhhh? Now I understand from this article that it is called “Randall’s Plaque” and because of it this is how my kidney grew such a large stone. Totally make since now. Thank you for an article so clearly written in layman’s terms. Not understanding what is happening to you is very stressful. Again thank you for helping me to understand and feel a whole lot better.

  9. bea russo says:

    How long does it take for a kidney stone to form

    • KidneyStoners.org says:

      Here’s the answer from our frequently asked questions page:

      It appears that stones can form in as short a period of time as three months. This is based on research of soldiers deploying to Kuwait and Iraq where the mean time to development of a symptomatic stone was 93 days in the hot desert environment. (Evans and Costabile, J Urol, 2005)

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