Video article: Supersaturation – The calcium crystals

IMG_2303This is a three part video about supersaturation, the most unique and critical measurement for evaluation and prevention of kidney stones.

Specifically it is about the calcium crystal supersaturations, calcium oxalate and calcium phosphates.

The main theme is how supersaturation can be produced and maintained.

Urine volume, excretion rates of calcium, oxalate, citrate, uric acid, and urine pH all affect supersaturation and are measured in routine 24 hour urine test panels.

We try to prevent stones by altering these excretion rates.

But crystals cannot ‘know’ anything about excretion rates, nor about a single concentration, like urine calcium or oxalate. Crystals know only the supersaturation, which reflects the products of calcium and oxalate or calcium and phosphate concentrations.

Although we treat excretion rates we really treat supersaturation.

Although we speak about stone disease as arising from abnormal excretion rates these abnormal rates can only express themselves in crystallization via increased supersaturation.

So supersaturation is a special, unique, and powerful expression of stone forming risk and occupies a correspondingly special place in pathogenesis and treatment of kidney stones.

It is their beginning and, when lowered enough, their end.

The massive importance of supersaturation has led me to summarize and dramatize it in video form, and I hope this will be of value to patients and their physicians.

Part One: What Supersaturation Is – 13 minutes

The Unique Importance of Supersaturation

Supersaturation is unique among stone risk factors because it is itself the force that produces crystals and therefore stones. It is measured against solubility, which the video tells about. Supersaturation is crystallization waiting to happen – a loaded gun.

Supersaturation is a Form of Free Energy

In the video changing the temperature of a saturated solution creates supersaturation. Kidneys supersaturate urine mainly by water extraction. Temperature change and water extraction do work on a solution like urine and that work is in part stored as the free energy of the high concentrations that do not immediately dissipate themselves in formation of a solid phase. As the video points out, solid phase will eventually form but in the meantime the solution has a potential not as yet realized, a potential for crystal and therefore – in our case – stone formation. That potential is supersaturation and, like all potentials, a free energy.

Part Two: How kidneys produce supersaturated urine, and its odd behavior – 16.5 minutes

The complexity of calcium oxalate can delay its formation

A supersaturated urine is ‘trying’ to create a solid phase and succeeds by chance, perhaps in seconds perhaps in days. This video illustrates what is happening in supersaturated urine as massive numbers of collisions between atoms and molecules create proto-crystals a rare few of which are sufficiently developed to ignite a crystallization cascade. The kidneys create the supersaturation in the course of water extraction, as a side effect of their life sustaining powers. The video introduces the main outlines of what kidneys do.

Kidneys supersaturate urine by doing work on tubule fluid

One cannot create a supersaturation without doing work on a solution, and kidney do the work that produces supersaturated urine – and therefore kidney stones. No other organs can do that work, so in the deepest sense kidney stones arise entirely from the work of the kidneys. The video sketches in the main outlines of how the kidneys do their work but I leave to a later series the details of it, details that deeply affect our treatments for stone prevention.

Part Three: How Supersaturation is measured and used in stone prevention – 23 minutes

Measurement of supersaturation is complicated

Commercial kidney stone testing laboratories need to provide supersaturations for millions of kidney stone patients and do so at a reasonable cost and price.

The video brings to life a wonderfully instructive way to measure it that is exact but too expensive to produce. Its alternative is a complex computer calculating engine that is the real source of the test results physicians and patients receive. How that engine works gives a deep insight into the complexity of urine stone forming chemistry and what we do when we try to alter it.

The originator of the computer program is pictured here. His name was Birdwell Finlayson and I offer him a brief homage.

Use of supersaturation follows the primary deduction of kidney stone disease

Being odd, supersaturation needs to be used in a special way, different from almost any other laboratory measurement. The video explores this ‘special way’ and presents what I call the ‘primary deduction of kidney stone disease’.

That deduction is, to me, the key to prevention.

It is, to me, the main theme of pathogenesis and treatment.

It is, to me, the center of this one special universe.

Links to the articles

Here are the links to all the articles about supersaturation on the site: The video sums them up rather well

Supersaturation and the stone crystals – Basic article

Supersaturation in clinical practice – How SS is used

Something you can do at home – Home experiment to make SS clear

Why 24 hour Urine: Supersaturation – The limitations and value of 24 hour average SS

The science of fluid prescription for kidney stones – How SS directs fluid use

Walking tour: Supersaturation – A summary article that adds commentary about many of the above

Art of stone prevention – A personal memoir of how I use SS in my own work


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Fredric Coe, MDTimLoretta Henrymichelle cavalierAl R. Recent comment authors

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I very much appreciate the work you’ve put into this informative site! I’m a student of veterinary medicine and was struggling a bit to understand the significance of testing for relative supersaturation in cats. This cleared things up very well for me!

Loretta Henry
Loretta Henry

Can a kidney stone be black. I think I passed something tiny black and somewhat like coal.

michelle cavalier
michelle cavalier

If you already know you have calcium oxalate stones, my husband passes one to two every other week. still want a straight forward answer about prevention.

Al R.
Al R.

Dear Dr. Coe, Thank you very much for another very helpful set of videos! These nicely clarified a number of things I had read your various articles. I had been wondering in particular about the effects of supersaturations stone formation vs. stone growth, and also how the supersaturations are actually determined by commercial labs. Regarding your request for feedback…Dividing it into three manageable parts seemed to work very well. The only critique I would have is that I found the slow character by character rendering of the titles to be quite distracting. That is in contrast to the other pans… Read more »

Elizabeth Kunz

Sorry don’t understand “moderation”?

Elizabeth Kunz

45 year old female
Multiple kidney stones (calcium oxalate)
In late 20s-33; then NO stones for 13 years; now 46, w/multiple stones–2 rounds Lithotripsys NO luck: Uteroscopy scheduled last friday…UPENN…early stage non-invasive Bladder Cancer found, removed, biopsied…Uteroscopy not done. Awaiting pathology confirmation while in CONTINUING STONE PAIN! Link between kidney stones and Bladder Cancer??? Any help, guidance, direction ?
Many Thanks, Liz

Midge gilmour
Midge gilmour

Thanks Dr Coe for your continued research. I continue to drink 120-140 oz. of liquid each day. I’ve moved to a warm dry climate. Should I increase my liquid even further?

Víctor Mateo
Víctor Mateo

Dear Dr: I am a fan of your publication but my english is very bad. Could you put the translation of your words in the vídeo? Thanks very much