CoeTie4Hard unwanted objects made in the kidneys, stones can cause pain, bleeding, and urinary tract obstruction. Because stone surgery often infects the urinary system, and bacteria easily infect stones retained in the kidneys, infection follow stones like a shadow.

Stones surprise patients by their smallness, for all the trouble they cause, or by their largeness to think they passed through the urinary tract.

But small or large, many or few, stones provoke little love. Most who form them desire no more. Yet left to themselves stones recur. Over half of first time stone formers form another stone within 5 – 10 years. Once recurrent, stones form – on average – every 2 – 4  years.

So stone patients must pursue prevention and not imagine their disease will stop of itself.

Prevention consists in the search for causes and the administration of treatment. This site exists to guide both.

Stones are hard because made of crystals

Urine proteins molecules stick to tiny crystals and to each other as if designed to dispose of unwanted things, and one can see in many morning urines tiny harmless crystal aggregates passed unknowingly and without harm.

In those predisposed, such protein crystal composites grow so large and numerous they can produce brief attacks of pain and bleeding but, being still too small to see on radiographs, escape detection. Such ‘crystal attacks’ are common in children with genetic hypercalciuria. Uric acid crystals can make a visible orange sludge or gravel.

When protein crystal composites grow grow big enough to obstruct the urinary tract and cause pain and we call them stones.

Very rarely urine organic molecules themselves make ‘soft’ stones that cause mild pain on passing.

Perhaps the true cause of stones hides in the chemistry of urine organic molecules, but for the moment these molecules are irrelevant to patients and their physicians. We do not know which ones most matter and about what is wrong with them that they permit stones we know essentially nothing.

So to prevent stones we work to prevent crystals. We search for causes of crystal formation, and act against them.

Stones are Crystal Artefacts

In human urine, calcium frequently crystallizes with oxalate and phosphate to produce the common calcium oxalate or calcium phosphate stones.

Other less common crystals form their own stones: Uric acid, a byproduct of nucleic acid metabolism; cystine, an amino acid that the genetic kidney tubule disease called cystinuria may liberate into urine in great excess; struvite, a crystal created by bacteria breakdown of urea, a normal urine constituent. Many drugs form crystals.

Because crystals can form independent of one another, many stones contain mixtures of them.

Like volcanic lava, an insect caught in amber, or the vague fossil tracings of some long lost species traced out in an otherwise indifferent rock, the crystals of a stone tell about a particular person with shocking precision and undeniable truth.

To find calcium oxalate crystals means such crystals were indeed once formed by that patient, and the same for all other crystals. Each crystal is a proof of past formation.

But unlike artefacts of a vanished age the proof in stones matters immediately, for in the person who made the stone those very same causes that once made its crystals may well yet operate and pose risk for more.

You might think such artefacts would attract the most intense interest and study. But no; stones are often discarded.

Stones Inform and Guide Prevention

Being as they are the artifacts and physical proof of past crystal formation, the crystals in stones guide all treatment. We can prevent stones only by preventing crystals. In any one patients the stones tell us what crystals we need to prevent. Otherwise than attend to the evidence written in stones we act in ignorance.

Stones are analysed by special laboratories

Specialized laboratories analyse stones at a moderate price.

One company has posted its prices. If you send the stone and pre-pay it is $40.00 with 2 photographs of the stone. Your doctor can get it for $35.00. This is only one of many companies that sell the service.

The report from any stone analysis laboratory is usually a single page that lists each type of crystal found in the stone and a rough approximation of the percentage of the stone each crystal accounts for.

The stones are powdered for the analysis. If you send a batch of stones, it will be cheap per stone but the powdering of the batch will mix everything together so you get an average. If all the stones are passed at one time, I would opt for a batch. If they were passed at different times, I would do them individually because things change.

General measures can help prevent recurrence in people who have formed only one calcium stone High Fluid Intake Trial

I think people have always believed that high fluid intake will reduce stone formation, although a detailed review of the literature has concluded that of all those published only one trial supports that belief and is well enough designed that it has credence. This figure from that one trial shows that formation of a new stone was delayed by high water intake in patients who had formed a single stone. After just one stone nearly 30% of people who did not increase their urine volume (Group 2, average 1 liter daily) had formed at least one more by 5 years whereas only 10% of those with a higher fluid intake (Group 2, 2.6 liters daily) did so. But it is hard to do everything with just fluids. The day is long and various. There is nighttime. People forget. Crystals never sleep. Crystals never forget. It may be true that in a trial, with prompting from nurses, people will maintain a high urine flow, but how about the usual situation? You want fluids. But you also want whatever treatment aims most precisely at the crystals you form. That means you need to know what those crystals are. And to find out what the crystals are the stones must be analysed.

Crystal specific treatment is far better than general measures for patients with more than one calcium stone

The patients in the water trial had formed only one stone each, so far as could be told, and only 25% of those who did not raise their urine volumes (Group 2) had another stone in five years. Among people who have formed at least several stones, 60% in the control groups of trials that tested specific treatments formed at least one more stone within 3 years, whereas only 15 – 20% of those receiving specific treatments formed another stone during the same interval. High water intake may well be ideal for those who have formed only one stone, but the large numbers of patients who have formed more than one stone will predictably form more stones at much higher rates and benefit greatly from treatments that focus on their specific stone crystal.

Return to Stone Walking Tour


  1. Nihal

    Dear Dr. Coe.

    Are most kidney stones somehow attached to the wall of the kidney? If so is it quite a strong bond?

    In my mind, I would think they must be attached, since if the stones are unattached and floating, most stones would come out through the ureter, while they are still small (i.e. they wouldn’t sit there and grow bigger).

    Also what are the densities of the stones compared to the density of urine? I would imagine that the stone density is higher than that of urine. Does that mean that if a stone has formed in a location that is lower than the opening to the ureter, such a stone would never come out on its own, and would just sink to the bottom of the kidney? (this would only be true if stones are not attached to the wall of the kidney)


  2. sanjeev mehta

    Please gibe me details of clinical significance of stone analysis, especially Calcium oxalate stones. Also suggest where I can get full details. Thanks
    Sanjeev Mehta

  3. Trish McClain

    Dr. Coe

    People are wanting to know what can you do about cystine stones? Some stoners are making a lot of them and having lots of procedures. They are tired of being sick.



Leave a Reply