MePhysicians can only do so much with stone prevention because a large part of the work can only be done by patients themselves.

The Five Steps to Stone Prevention, the two articles on how to read your 24 hour laboratory reports for calcium and uric acid stones, and the article on how to be a successful kidney stone patient are the reference materials you need to accomplish your part of your personal stone prevention program.

It is now time to pull these four articles together into an organized approach that any patient can follow.


Before your visit to decide on prevention Read the article on how to be a successful kidney stone patient, where  you will find lists of materials to bring with you. 

Know your stone type(s).

Get the right blood and 24 hour urine testing.

Read your own 24 hour urine laboratory reports and make notes so you will be fully prepared to make use of what your physician knows

Perform what I call the ‘Great Integration’ and have it ready as a key part of your discussion with your physician.


How, exactly, do you prevent what you do not know?

Stone analysis is the foundation of your prevention.

Find past analyses. If you have stones in your possession, get them analyzed.

If there never have been any analyses and you have no stones, make a good guess. Part 1 of Five Steps details an approach, so read it now if you do not know your stones.

Do not give up easily. Someone, somewhere, may have your report. If all you can do is guess, guess as best you can. Have your physician guess, too.


The needed blood tests can be obtained from any certified laboratory. Be sure they are fasting.

Proper 24 hour urine testing is best done through one of the national vendors of such products. Local hospital laboratories are not ideal and often simply send the urine out to such vendors with high possibility of adding errors. Vendors provide home collection and mailback materials, and issue a graphic and complete report of all measurements including supersaturations.

Much of the value of your 24 hour testing is determined by your behavior. You need to collect so the results reflect your average life conditions. If you show off and drink a lot, you will be fooling yourself. If you collect only on a weekend day, likewise. Two collections are much more valuable than one. If a collection goes badly – loss of a sample, uncertain timing, throw it out and do another – it costs nothing and prevents mistakes.

You are the one who times your collections. Make a copy of your start and stop times, so you can compare your results to those in the final report. Sometimes there is a mistake in transcribing.

You will measure the urine volume in many cases, or can measure it from markings on the container. Write them down in case there is a question of errors. The largest vendors, Litholink (a branch of LabCorp) and Quest actually infer the 24 hour urine volume and do not use your measurements in most cases. They add one or another proprietary marker to the collection container and measure its concentration. This latter tells them the volume in which the material has been diluted. That volume is the 24 hour urine volume. Here and there, though, if you have measured carefully your measurements may help resolve problems when the multiple samples from you fail to match in their completeness of collection. For your measurements to be useful, you need to read the volume as precisely as possible – get as specific a reading from the measuring scale as you can – and write the results down.


As I launch into this I want to make clear my intent is to enable patients to make the best use of their physician visits. You need a physician, but you can do a lot before the visit to become thoughtfully informed and thereby be a more useful partner. If you have thought through your own information the time you have together can be used for more detailed explanation and less for routine matters you can do beforehand for yourself.


Find the 24 hour urine creatinine excretions and see if they match within about 15 percent. If not, one is wrong. Recheck your timings. If you think the urines were perfect, call the vendor and check their times and volumes. If times and volumes match and the creatinines do not match you probably have made a mistake and you should get a third as a tiebreaker before going to your physician.


Abnormal means the 24 hour value is known to be associated with risk of stones. Mostly the associations are from prospective observations. Some are based on very firm physical chemistry. The following is directly from the two articles on reading 24 hour urines for calcium or uric acid stone risk.

Write down each of the following that is abnormal – this is your list of abnormalities that are candidates for treatment

Urine Volume below 2 liters per day is abnormal – low flow

Urine calcium above 200 milligrams per day is abnormal – called hypercalciuria

Urine oxalate above 35 mg per day – called hyperoxaluria. (Strictly speaking, values above 25 mg per day are abnormal in that an association with stones can be detected above it. But most people indeed excrete more than 25 mg of oxalate, so a more practical level is above 35 mg per day).  Hyperoxaluria is almost always due to a high diet oxalate intake, low calcium diet intake, or both. Values above 80 mg per day are very unusual and may reflect a systemic disease – your physician will note this – be sure it is discussed.

Urine citrate below 400 mg per day is abnormal – called hypocitraturia.

Urine pH below 5.5 confers a risk of uric acid stones – low urine pH

Urine pH above 6.3 confers a risk of calcium phosphate stones – high urine pH

Urine sodium above 100 mEq per day is above the recommended for US population – high sodium intake

Urine sodium above 65 mEq per day is above the optimal intake for the US population – above optimal sodium intake


Supersaturations are not compared to normal or to stone risk because we lack the critical information. But we know one thing: If you are forming new stones, the supersaturations for the crystals in your stones are too high and need to be lowered.


Here it is, and you are ready.

This is a breakdown of what is already said in another article.



Think about it and make your own decision. When you see your physician, he or she will read your scans with you and count if stones are increasing or decreasing in your kidneys. You will have gathered all your old records and will know when stones have passed or were removed. Your physician may have more such information. Decide if new stones are indeed forming.


We have been here before – most critical to know.


Write them down; these are your relevant supersaturations


This can be confusing so lets review things.

The purpose is to lower by half or more the supersaturations in your urine related to the crystal(s) in your stones. If your stones are mostly calcium oxalate then calcium oxalate supersaturation is your main target. If your stones are mainly calcium phosphate then calcium phosphate supersaturation is your main target.


Correct abnormal urine volume, calcium, oxalate and citrate in that order or priority. For calcium I have linked to idiopathic hypercalciuria, being the usual cause, and that will link to diet sodium and diet sugar as factors your can correct without medications. If your sodium is above optimal (see above) lower it. If you eat lots of sugar, stop. Then, when fluids and diet are both corrected recheck. If CaOx SS has fallen by half or more that may be enough. In principle you could wait and see if stones are now prevented – time will tell.

I am not saying that you treat yourself nor that this is an approach written in stone. I am saying this is a common strategy that your physician may well want to use. There may be reasons not to: You have had too many stones; you have only one kidney; risk to your general health of any more stones is really high.

Thiazide diuretics are a next step when fluids and diet have failed to lower supersaturation enough or new stones form. They should usually not be a first step but rather when follow up 24 hour urines demonstrate that urine supersaturation has not fallen by half or, if it has, if observation shows you that new stones are still forming. Potassium citrate is like thiazide as it will lower urine calcium – not as dramatically – and lower supersaturation by binding calcium, as well as inhibit crystallization. But this agent has become expensive, and is always hard to take because pills are big. So thiazide is a more common first drug.


Correct abnormal urine volume, calcium, pH, and citrate in that order of priority. High volume (above 2.5 liters) is a very useful step here because it can be sufficient in some cases. Calcium is as for calcium oxalate: reduced sodium and sugars, thiazide diuretics is needed when diet and fluids have failed. Urine pH elevation in calcium phosphate stone formers is usually innate and not directly amenable to change but there are odd situations where this is not true. Sometimes people take in very large amounts of fruits – especially smoothies – compared to proteins and have an alkaline diet. One can try rearranging things if you are like this. Potassium citrate is an uncertain treatment here because no trials have been done for calcium phosphate stone formers.


Correct abnormal urine pH and volume in that order of priority. This is the easy one – raise the urine pH, almost always with potassium citrate or other alkali formulationsWhatever uric acid has been forming will form no longer, and some may dissolve.


This is not for you to figure out.

A good screening table is in Five Steps. It requires blood and 24 hour urine measurements and a physician to interpret them. Do not try to figure this one out yourself – it is not wise nor is it practical or safe. Most stone formers do not have such diseases but those who do are in a different realm than the rest. Sites like this one, even though medically rigorous, cannot guide patients with these diseases but only inform them.

The table is not comprehensive nor meant to be. It is a table of highlights. I know many more rare and obscure causes, and so do your physicians.

By all odds you do not have any of the diseases. But do not assume.

Be sure with your physician.

If you have a systemic disease, much of the foregoing will become subsumed in systemic treatments, and these are beyond what we can do here.


Between Five Steps, How to be a Successful Stone Patient, and the articles on reading your reports you are ready to do your best when you see your physician. You should expect to leave with mainly lifestyle and diet changes after a first visit, and plans for a follow up with labs in a month or two. Every cycle is the same, however, until you have reached your supersaturation goals and stones no longer form.

I hope these articles help you achieve what we all want. Let me know. Write a comment. Being only electrons, these articles can be reshaped any time, but it is really patients who can tell me how best to do that.


  1. Amber

    Hi there,

    I feel chronically dehydrated. When I get sick with small amount of vomiting or diarrhea, I require IV. The only result that’s been concrete is low volume. I have sand like stones filling both kidneys. I haven’t been able to catch/analyze them. My anion gap stays on the high side (not high, just highest to be normal). My sodium & potassium stay low. I increase my sodium intake to not feel chronically dehydrated. Any lifestyle choices I can implement to feel hydrated & avoid producing more sand like stones? Thsanks

    • Fredric L Coe, MD

      Hi Amber, Are these dehydration attacks with stones or seeming to be a cause of stones? I have seen this, but it is not clear from your note. The sodium and potassium, are these in the blood or urine, likewise the anion gap. If you fill in these questions I can try to help. Regards, Fred Coe

  2. Albert

    Hello Dr. Coe,

    (1) CT scan shows I have a 5 mm dependent stone in the bladder. The doctor wants me to do an ultrasound a month later to see if the stone has passed. I wonder if ultrasound is good enough for a 5 mm stone? Shall I do another CT instead?
    (2) The CT report says my prostate measures 5.6 cm. What’s the equivalent weight or volume?
    (3) How long do soluble oxalates stay in one’s digestive tract? Can I separate the time of eating oxalate food and the time of drinking milk by 15 minutes to half an hour?
    (4) How much milk shall I drink to bind every 10 mg of oxalate (or soluble-oxalates) in food? Is there a recommended ratio?
    Thank you.

    • Fredric L Coe, MD

      Hi Albert, I think ultrasound should be suitable – your urologist is the best expert for that because she/he knows exactly where it is and if it can be seen. As oxalate, it is absorbed in the colon. If you eat the calcium products with the oxalate products, they will get to the colon more or less at reasonably close times. There is no known human data on the intake ratios. All that exists is in the graph showing effects of diet calcium on urine oxalate – a copy is in this article. Regards, Fred Coe

  3. Albert

    Hello Dr. Coe:

    I have “kidney stones” detected by ultrasound and I have blood in urine after workouts. My physician wants me to take a “CT Urogram”. However his CT order form says it’s a “abdomen/pelvis CT scan w/o contrast” and the it’s for “bladder stones”.
    (1) Is “CT Urogram” the same as “abdomen/pelvis CT scan w/o contrast”? I got conflicting answers so far.
    (2) Is it important to mention “kidney stones” and/or “bladder stones” in the CT order form? Does it make any difference to the ultrasound technician?

    Thank you.

    • Fredric L Coe, MD

      Hi Albert, Your physician has ordered the right CT. The radiologist will read the CT for stones anywhere they lodge. Regards, Fred Coe

  4. Stephanie V

    Hi, I am a 42 female, diagnosed with MSK in both kidneys. I’ve passed over 300 stones since my first one at 28. MSK was missed until last year. I’ve only had to have 2 surgeries on stones until last year. I had a percutaneous nephrolithotomy last Oct to remove a stone over 1/2 the size of my kidney and clean out the rest. Three months later, I was back to kidney impacted with stones (right kidney has quite a few but not that many presenting/reoccurring problems). The last 2 months have been rough. I am tired of fighting something I can’t seem to control. I had emergency surgery 3 weeks ago to place a stint, and they tried getting the stone this last Wednesday….no luck. Yet, since stint placement and time passed to get the stone, a 2.5cm stone has been discovered in addition to 10mm stone stuck in ureter. They are going to want to do another percutaneous surgery. Never again, I cannot do it anymore. Went to see specialist at Mayo 3 weeks ago. I have no answers. Autotransplant kidney surgery has been suggested, Mayo doc says really bad idea. I’m about to the point of just saying take out the left kidney if right can function ok. I’m never thirsty and to the point I don’t even want to eat. Oh, I also have heart problems. This is just no way to keep living. Any suggestions on where I can really get some much needed help?

    Best Regards,
    Stephanie V

    • Fredric Coe, MD

      Hi Stephanie, You have two problems. One is surgical and best handled by consulting another surgeon – one with a very high level of skill. I could recommend Dr James Lingeman at Indiana University, or Dr Manoj Monga, at Cleveland CLinic. They are specially skilled, even beyond what you might get at Mayo – in my personal opinion. You also seem to have a very aggressive form of stone disease – you did not mention the stone type – that will have evident causes on serum and 24 hour urine testing, causes that can be corrected to prevent so many more. If you tell me where you live I can suggest places to consult at. I gather Mayo did not address this issue. Regards, Fred Coe


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