THE FIVE STEPS TO STONE PREVENTION

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

143 Responses to “THE FIVE STEPS TO STONE PREVENTION”

  1. Kathryn G

    Hello! Thank you for all the information you have given through the web. It helped me make sense of the test results I just received. I had a kidney stone test to test the crystals that are consistently in my urine – causing cloudy urine. My crystals are 20% ammonium hydrogen urate and 80% struvite. Ironically, it looks like the treatment for either of these individually is exactly the opposite of the other. I was wondering if you would be willing to comment on the test results. Thanks for considering this :).

    Reply
  2. Ginger Saalbach

    I am trying to figure out my test results. I do not see my urologist until 2 months from now, but would love to get a kick start on whatever I need to do. Can I send you the results?

    Reply
    • Fredric Coe, MD

      Hi Ginger, I would be remiss if I did this as it were practicing medicine for someone I do not know. If you want to post the results I can comment technically on what the numbers show – many have done this – and being public commentary I would be within proper bounds. Regards, Fred Coe

      Reply
  3. Joe

    3 weeks ago I had a ureteroscopy which removed a 6mm calcium oxalate stone. I continue to get intermittent flank pain on the affected side but only when I urinate. Is this another stone that wasn’t picked up on CT or just residual reflux from the hydroureter caused by the original stone?

    Reply
    • Fredric Coe, MD

      Hi Joe, I cannot be sure which is the cause, but if it continues your urologist will want to look into that cause and be sure things are alright. If you are a physician, which I suspect, indeed there may be residual hydroureter; but sometimes there are residual fragments, and sometimes the hydro has not resolved because of residual obstruction. So I would be sure. Regards, Fred

      Reply

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