CoeTie4At the end of it all, the science, the medical visits, the surgeries, what we really want is to prevent new stones. That is the main goal. Modern surgery is a blessing for those with stones. But no surgery is far better than even the most skilled and effective surgery.

Prevention of stones is orderly and occurs only over time.

Here is how to do it.

This article is designed to go with my other one which tells how to organize your medical visits so as to achieve these steps. 

What is the Science of the Five Steps?

Stones are made of crystals.

Supersaturation drives crystal formation and growth – this is a physical law that must always apply.

Supersaturation measurements are widely available from commercial vendors.

Because people who are actively forming stones are forming crystals their supersaturations are too high – crystals are forming – with respect to those crystals.

Lower the relevant supersaturations and you must lower formation and growth of those crystals in their stones.

With respect to the most common stones, calcium oxalate and calcium phosphate, and uric acid, supersaturation in urine depends mainly on volume, calcium, oxalate, citrate, and pH. You can lower supersaturation by altering any or all of these in a given person and so far as crystals are concerned the effects are much the same. 

1. Know the Stone Crystals

Stones are made of crystals: No crystals no stones. Prevention is prevention of crystals.

Analyze Stones

The proper way to know the crystals is analysis of stones and their fragments. Stone analysis is not expensive. If imperfect, it is the best we have, so use the service liberally. Stone crystals can change, and therefore prevention can need to change direction. There is no reason to discard a stone without analysis just because we think we know the answer.

Uric acid stones are remarkably easy to treat by raising urine pH and require little more discussion.

Cystine stones arise from hereditary kidney transport disorders and require special management.

Struvite stones arise from infection and require special combined surgical medical management.

Drug stones, ammonium acid urate stones, and rare stones – eg. 2,8 dihydroxyadenine stones require special management.

The vast proportion of kidney stones are calcium oxalate and calcium phosphates and uric acid, and this article refers mainly to them.

Guess if You Have To

Red or orange stones probably contain uric acid. Likewise, stones that do not show up on simple abdominal flat plate x rays are probably uric acid. These are easy to prevent, and recurrences are unnecessary.

Allow me to elaborate on this. Pure uric acid stones are almost all due to an excessively acid urine pH, and will stop if you raise that pH. Potassium citrate tablets, 10 mEq size, 2 twice daily is almost always enough. Sometimes it takes 2 tabs 3 times a day. Crystal light lemonade has in one liter about the same amount of alkali as two of the tablets. I could say that there is little excuse for another uric acid stone.

If stones contain uric acid and other crystals, those other crystals need to be dealt with on their own. They may not respond to higher urine pH, and could be worsened.

Yellow stones are probably cystine, and due to cystinuria, a complex disease with its own special treatments. Because almost all kidney stone panels include a cystine screening test, cystinuria is almost never missed. A positive test, however, can reflect cystine trait and the stones can be something else. So it is the negative test that is fully informative.

Small black stones are probably calcium oxalate, and large very homogeneous hard stones are probably brushite. But one cannot be sure.

Big stones that fill up the interior of the kidney are usually cystinestruvite – from infection, or calcium phosphates from alkaline urine and hypercalciuria.

But guessing is not a good way to achieve prevention. Find out whenever possible what crystals you are trying to prevent. Any stone fragment can be analysed. Never pass up an chance to be sure.

2. Obtain Proper Blood and 24 Hour Urine Measurements

I prefer two 24 hour urine kidney stone risk panels as a minimum along with at least one set of fasting blood measurements.

Screen for Systemic Diseases

Here is a table of systemic causes any physician can follow using the blood and 24 hour urine testing. This is not something a patient can do anything about except see that it is accomplished.

Revised Table for Evaluation for Systemic Causes of Stones

The bowel diseases that cause enteric hyperoxaluria – small bowel resection, malabsorption, are usually obvious, as are ileostomy and bariatric surgery.

Medullary sponge kidney and nephrocalcinosis are complicating features physicians need to deal with. Medullary sponge kidneys actually form tiny micro crystals in their dilated ducts. Whether these grow to become clinically important is not clear.

Nephrocalcinosis simply means many crystals are present on x ray images. During ureteroscopy these crystal deposits can be sorted out into real stones and plugs within the terminal ducts of the kidneys. Pain without obstruction is widely described in both of these conditions which complicates management.

Measure Urine Supersaturations of the Stone Crystals

Standard 24 hour urine kidney stone risk panels give supersaturations along with the urine chemistries that control those supersaturations. These are the keys to prevention. Supersaturations control crystallization and can be measured reliably in people. If crystals are being formed the supersaturation is too high and we need to lower it.

Read Your 24 Hour Urine Reports

Your physician will take care of you but a prepared and educated patient can make that care vastly more effective and reliable.

You can understand your 24 hour urine tests and follow along with your physician during your visits and when treatment has been introduced and your urine chemistries change as a result. The details of interest are different for calcium stones and uric acid stones, so I have put them in two separate articles. Do not be put off by all the numbers. Follow the articles with your test panel in hand and you will find things are not so difficult.

Stone prevention is long term and involves changes in diet and behavior and, often, medication use. If you can read your own report you will have a first hand sense of why your treatments are good for prevention and whether your treatments have achieved what they were designed to achieve.

3. Lower By Half the Supersaturations for the Crystals in Stones

There is no one way to reduce supersaturations. Every patient will have a characteristic pattern of abnormalities and supersaturation can be lowered by changing any number of those abnormalities present. Below is my general strategy, but it may not apply to you. If your urine volume is already very high, for example, to raise it would be silly. So consider my ‘strategy’ a general set of rules, easily modified to fit the individual situation.

Raise Urine Volume as High as is Practical

Above 2.5 liters daily is ideal. The site is very rich in advice for fluid treatments. How to drink more. How to get variety. How to avoid low flow periods. Being without cost or risk, fluids are always my first choice.

Reverse Urine Abnormalities Raising Supersaturations for the Crystals in Stones

urine calcium oxalate volume and citrate vs risk of stones from Curhan plotted with identical risk axesIdentify the factors in the 24 hour urine beside volume that are raising supersaturations for the crystals in stones, and act so as to reverse them toward normal. Common ones are high urine calcium, high urine oxalate from diet, low urine citrate, and low urine pH – for uric acid stones. High pH is a risk factor for calcium phosphate stones but one cannot lower urine pH under most circumstances.

Bang For the Buck

A vulgar phrase, if you think about it. Here are the relative risks of becoming a stone former in the three cohorts of nurses (red) and physicians (males, blue) Dr. Gary Curhan followed. You might say relative to what. For each risk factor it is different: Calcium – less than 100 mg/day; Oxalate – less than 20 mg/day; Citrate – less than 300 mg/day; Volume, less than 1 liter.

The average relative risk is at the end of the crosshatched bars. The ends of the solid bars are the 95th percentiles. When the solid bars are above one risk is certainly present, so you can see the safe ranges for calcium, oxalate, citrate, and volume. Because the plots all have the same risk ranges you can compare these four risk factors. Calcium has the widest  effect range. Oxalate is next and increases risk at even 25 mg/day. Citrate causes risk only when below 400 mg/day, and volumes above 2 – 2.24 liters lower all three cohorts into a low risk range.

Although urine volume confers relative risk equivalent to high urine calcium and oxalate only when below 1.25 liters daily (see graph at left), one always wants to raise it as much as is possible because such treatment is without risk or cost. Above 2.25 liters daily is ideal. The site is very rich in advice for fluid treatments. How to drink more. How to get variety. How to avoid low flow periods.

Obtain New 24 Hour Urines to be Sure Supersaturations Have Fallen

There is no point to changing diets or medications without proper follow up to determine if what was done had the desired effects. Six weeks is a good time for the first follow up measurement. Continue measurements until the supersaturation goals have been achieved.

4. Obtain more 24 Hour Urines if New Stones Continue

Crystals follow physical laws and supersaturation is what drives them to form and grow. Continued stones with reduced supersaturations means either supersaturations need to be lower, the 24 hour samples are not being taken on representative days, or the days themselves have periods of low urine flow or other breaks in treatment.

Crystals do not sleep nor do they make mistakes. Any chances they get, they use.

Physicians are trained to ferret out the details of a patient’s history that matter here. It is my main clinical expertise. 

Patients are not trained but they are the ones sitting up close at the 50 yard line. So they know more than anyone else. They just may not know what is important for stone prevention.

5. Follow Up Every Year Thereafter Even If Free of New Stones

OH, you might say, those urine measurements cost money.

They do, hundreds of dollars for each one.

The merest surgery can cost near to or even above ten thousand dollars when you consider the total of medical, operating room, anesthesia, and pre and postoperative imaging costs, and the inevitable emergency room visits that provoke the surgery in the first place. This is not to mention lost time from work.

And, did I speak about pain, misery, infections?

It it time for blunt talk. Lab measurements are the compass and altimeter. Flying blind is silly.

A Good Way to Get All This Done

You cannot do the five steps alone, your physician is crucial. He or she cannot do them either; you are crucial. In case you missed it, here is my view on how a patient and physician can best partner for stone prevention

That’s It

This site is far from complete but it already has a lot of what one needs to carry out these five critical steps. Do them and new stones will cease altogether or at least greatly reduce in frequency. If it does not work, one or more of the steps need correcting. After nearly 45 years preventing stones, I have become bold enough to say this, and mean it.

Good Luck, Fred Coe


  1. D. Clewett

    HI Dr. Coe. I’m new to the stone world. I think I passed a kidney stone two years ago; went to the ER for discomfort but nothing special was done afterwards. This past July I had over a 1 cm stone in my left kidney with infection. I had the laser procedure to remove it 2 weeks later in after the infection cleared up. Teh problem is I do not know officially what the stone was made of- my urologist keeps telling me it sometimes takes weeks to get a result back; I checked again with him last week but he says he still doesn’t have any results. My 24 hr urine test was somewhat botched because I went to the ER for extreme pain near my left hip during collection time (so IV, urine collection, and throwing up from the pain meds- passed a 2 cm blood clot and a 5 mm stone about a day later). Regardless, I do understand I need to increase my fluids, lower my protein and sodium intake, watch my sugar (also newly diabetic) and am following your Low Oxalate Diet. I just have a feeling I am frustrated that I may never know my stone composition at this point, but keep hoping something comes in. I am also thinking about finding a new urologist and would like to ask you for any recommendations for one in the far western suburbs of Chicago. Thank you.

    • Fredric L Coe

      Hi D., The stone analysis is crucial to planning treatment, and if the 24 hour urine was botched just do another one as it is equally essential. Low oxalate diet is not always important, so wait for the urine results. I am afraid that even though I work in CHicago I am not familiar with urologists in the far Western suburbs; the university of Chicago is far east. Regards, Fred Coe

  2. Marcus Krafft

    Thanks for your artice. I have passed one huge stone 2 years ago. I have been drinking more water and not had another stone. Ultrasound shows a cortcal stone in one kidney, but I am always told not to worry about it. Any ideas?

    Also what is a good target ph for stone prevention? I will use Uralyt-U. I am in Thailand.

    • Fredric L Coe

      Hi Marcus, so you have had one stone without recurrence. I always vote for serum and 24 hour testing to figure out what is wrong – just as in this article. Then depending on results, you can take rational action, perhaps nothing more than fluids or more if abnormalities are marked. You are taking potassium citrate, I presume, and being safe I see no reason not to do this. If Thailand has no 24 hour urine testing, perhaps you can get tested when visiting other countries. Regards, Fred Coe

  3. Michelle Scanlon

    Dr Coe – I had my first lithotripsie and stone last year June/2018. I had horrible back pain before I had the lithotripsie procedure on my left kidney. I had a follow up appointment in April to see if I was developing any more stones, I was told everything was great. My back started hurting on my right side this time and my urine was dark so I called their office in July to see what I needed to do. I went in for a urine test and it was positive for e-coli bacteria. I learned that my results from April showed that I had had bacteria in my urine and that I had a kidney stone in my left kidney again. I was upset since no one ever follow up with me after my official results came in to their office (radiologist reading and lab results) I had no other side effects of infection except dark urine and severe back pain that I was feeling on my left side since there was no stone present in that kidney. It took two rounds of antibodies to get rid of the bacteria and the third test was negative of that bacteria but positive of Lactobacillus species which they indicated they don’t treat. I think that original bacteria has come back again since my back is starting to hurt again on my left side. I am prone to UTI’s. It seems I had bacteria in my urine last time I had kidney stones too. I was able to finally see my doctors partner since she was out of town.I indicated to him at that time I was also passing black pepper like specks and settlement, I also mentioned my concerns of the bacteria being present with the stone since it was there constantly last time I had stones but he was not concerned and did not seem to think there was a correlation. He said it would be a different bacteria that caused them. He ordered a 24 hour urine test. My results came back as SS CaOx 6.11 Urine Calcium 223 Urine Oxalate 39 The interpretation of lab results: *Urine Calcium borderline elevated *Borderline Hyperoxaluria *Mild CaOx stone risk. I have been reading it might be my parathyroid having issues. I also read that I should take calcium. Do you know what I should do about stones? Do you know what I should do about UTI’s and bacteria? They maybe two separate issues but I need both addressed. Since I have absolutely no faith in my current Urologist or their office staff, do you know anyone in the Atlanta area that would be able to help me? Thanks in advance!

  4. Ann Petersen

    Hello Dr. Coe, as an information seeker, I am so grateful I have found this website. After reading 50 different sites about “oxalate content”, I’ve found your “how to eat a low Oxalate diet” especially valuable! On 9/30/2016 an ultrasound revealed 1. Few parenchymal echogenic foci measuring less then 0.5 CM, bilateral kidneys, consistent with localized fat, prominent vessels or calcifications (calculi). 2. Minimal collecting system dilation and/or subcentimeter parapelvic cysts, right kidney. 3. Prominent column of bertin, right kidney (normal). I read stones of 5cm (if they were) could just pass naturally so I increased my liquid consumption to 75-90 oz/day. Using a sieve, I think I did collect a 1ml stone I bagged up ( tan colored) but never got it analyzed. I live in Glendale, CA and have many options to care, but wondered if you know of a doctor on the more conservative treatment side? I think CedS is a wonderful place, had 1 surgery there, excellent results, but also have declined 3 others with excellent results. My gynecologist sent me for the ultrasound in 2016 & said yesterday I should have followed up it could be a 10cm by now. I am going to get another ultrasound so that’s why I am asking if you have a referral. Thank you for your valuable time

  5. Jon

    I wondered if you ever thought about toothpaste as a main re-occuring cause of stones. My dentist was telling me I need to brush to re-mineralize my teeth; I often enjoy the taste and used to just ingest a portion of it brushing. Combined with the fact I noticed a special toothpaste with the warning to rinse out numerous times to avoid ingesting the minerals??

    I also read your piece on supersaturation and 24 hour urine collections. I have disordered sleeping patterns due to a sleeping disorder and a neurovascular condition that requires I sleep during the day. I have been known to sleep for as long as 22 hours at a time. And be awake just as long. Of course I cheated when they had me do a 24 hour urine I just did it when I was awake to impress them with a gallon of urine – I’m waiting on the Citrate levels, they didn’t get any of the concentrated morning urine void. The labs instructions fail to plan for people that are not on a 24 hour sleep cycle, and there are many of us. Your supersaturation theory sounds plausable, But I also have imagined that after sleeping for about 8 hours it is possible that since no more sodium or minerals are going in. That perhaps with nothing going into the kidney there is no supersatuaration. The only way to find out would be to collect a 24 hour urine from someone that is sleeping for about 20 hours. This might prove or disprove your supersaturation theory. The next time I do my 24 hour urine I will only give them concentrated urine. However, a normal person could probably duplicate this by just giving them only nighttime urine and 2 first morning voids(over 48 hours), without drinking water before going to bed. This would prove, or disprove, the supersaturation theory.

    BTW, I haven’t had a stone in 5 years with 10 Meq potasium Citrate 3x or 4x per day. I also drink those 0 calorie “clear” diet citrus drinks that have citric acid, and potasium citrate. Pre Kidney stones I used to consume 6000-8000 mg sodium from junk food and I am slender with a belly.

    • Fredric L Coe

      Hi Jon, We have no data on altered sleep cycles, as you point out. But we have good data that SS is highest at night even though excretion rates are low because urine volume falls drastically with sleep. Possibly you have very high SS while sleeping. But since no new stones have formed, perhaps things are alright. As for toothpaste, it is not ideal to eat much of it because it contains fluoride and that can stain tooth enamel. Regards, Fred Coe

  6. Stephanie Flores

    Hi Dr. Coe,
    I had my first kidney stone 2 years ago and have had 6 others that I may or may not have passed and currently have 12 between my 2 kidneys, the majority being in my right side. My CT scan in November showed these stones, with the one I was trying to pass at that time being 6mm. Since then, I have had 3 other “major” pain sessions, but go in and out of pain, sometimes several times a week. I will be fine and then boom 💥 I start hurting. On top of that, my blood pressure has gone up and is now staying around 140-150 over 98-101 most days. My primary DR is Internal Medicine but hasn’t really been able to help me much. I went to s kidney doctor and they really didn’t help either. At this point, im being told to see a urologist. I am in Texas, a little north of Houston… know anyone in the area that I can actually get some help from?

    Thank you!

    • Fredric L Coe

      Hi Stephanie, you seem to have a complex problem and need real experts. My choice is UT Dallas, that has a wonderful mineral center and specializes in kidney stones and bone disease. Dr Sakhaee or Dr Orson Moe would both be excellent choices. Please feel free to say I sent you. Regards, Fred Coe

  7. Lisa

    I have had 4 stones in the last 4 years….my doctor has not put me on anything to stop these stones – just had another analysis and my SS CaOx 9.86 and SS CaP 2.84 — is there anything I can take to prevent them>

  8. Susan Gough

    I just had my first kidney stone and developed Septic Shock, Flash Pulmonary Edema, and Takotsubo Cardiomyopathy because of it. I was in ICU twice and on a ventilator. I almost died twice. I am terrified that I am going to get another stone. I need to find another Urologist since the one I have only told me to eat healthy, lose weight, and exercise and he would see me again in 3 months. I just had my stent removed 2 days ago after having it in for almost 2 months. Do you know a good Urologist in the metro Detroit Michigan area?

    • Frederic L Coe

      Hi Susan, What a terrible event. In Detroit Wayne State has no urology faculty I recognize. U MIchigan at Ann Arbor has a large urology department and likely higher quality. Dr Roberts in that department lists himself as an expert in endourology and must be their main stone surgeon. I do not know him, but I would make inquiry if I were you. Regards, Fred Coe

    • Denise

      Susan… I just saw an amazing urologist in he Detroit area. I have been plagued with kidney stones most of my life and she is one of the first Drs who has done a thourough work up and has advised me on prevention. Dr. Shiva Miralania

  9. Jeremiah Bishop

    Hello! I was hoping you could refer me to a doctor in MI for my gf.

    • Frederic L Coe

      Hi Jeremiah, I can try. I presume your gf (girl friend) has stones. Can you tell me where in MI she lives so I can get the closest for her? Regards, Fred Coe

  10. Robert Steinberg

    Hi Dr Coe, thank you for your wonderful website. Do you have the name of a doctor in the San Francisco Bay Area you could recommend? I had one large Uric stone that was removed through lithotripsy about ten years ago and I don’t want to go through that again. I have been put on six 1080 mg pills of potassium citrate per day and was trying to get another opinion if this is the best solution. It is a bother and will be very expensive when I go on Medicare later this year. Thank you for your anticipated courtesies and your wonderful work.


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