One Paper We Never Wrote

joan at quad partyThere was and is a list of papers we never wrote. At the top of that guilt making list is the paper on “Low Flows”.

You, who are being encouraged, nagged, exhorted to drink more water will be familiar with the reasoning – dilute the stone forming salts. Why, you think, do I form stones and those of my friends and neighbors who drink no more than I do, do not.

The answer, in short – is that you cannot get away with it. Whether you have elevated urine calcium or for some other reason, you cannot get away with it and must drink more.

What is a “Low Flow”?

It Is Not Evident at the Beginning

There is a persuasive thought that if you are a stone former, then you are a low flow because at your regular urine volume you are at risk, so therefore you should raise it. If the urine volume permits stones, it is too low.

True, but that is not what I mean by Low Flow.

Lots of people come in for their first collections with a low urine volume; they just never knew that for them a low volume could promote stones.

With advice, many raise their volume and that is that, at least so far as volume is concerned. These are not low flows.

It is Evident After a While

If after you have been counseled to increase your urine flow and there is still a 0 heading your liters of urine volume per day then it is obvious – 0.9, 0.8 liters a day: You are likely to be a low flow.

If there is a 1 in front of your volume, then you are still probably a low flow.

Probably becomes certainly if this pattern persists for a few more tests.

The numbers tell the story – those paltry urine volumes announce themselves and can’t be gotten around.

You are a low flow and you are at risk.

When your urine volume begins with a 2, you are no longer a low flow.

Where Did I Get My Numbers?

Epidemiological links between becoming a stone former and urine volume have been discussed on this site already. Above above 2.5 liters daily is no longer associated with stone onset. 

Another approach: Supersaturation is the key to crystal formation, and it falls steeply as urine flow rises. Values above 100 ml/hour, or 2.4 liters a day, are on the plateau.

Then, there is common sense. The urines with 500 ml or 1000 ml are obviously concentrated. I have seen them. They are dark and ominous looking. Patients all know this; they tell us so.

Some People Can’t Drink Enough Water

Their Lives Interfere

Although we never wrote the paper, intuitively there are people who are low flows because of their lives.

Those who work in a hot environment such as short order cooks, chefs, bakers, outdoor construction workers, mill workers, welders.

Police detectives and special agents on stakeouts.

Airplane pilots who live in a parched environment of plane flight. They are free to leave the controls to use the restroom, but the environment is dehydrating. Pilots on small regional commercial planes can have special problems: Some fly alone; some planes have no bathrooms.

Frequent travelers who either become dehydrated on plane flights, or those who have long car commutes that they cannot interrupt to use a restroom.

High school students who live in a rigorous environment that does not allow for bathroom breaks, even if the bathrooms are safe.

Mothers who attend all of their offspring’s games and decline to use outdoor facilities.

Surgeons who have long operating room times.

Lawyers who are litigators.

The list goes on into infinity. Once these people realize the problem, then ‘work-arounds’ may be found, usually by them, to raise their volume enough to protect them against more stones.

Their Bodies Interfere

It happens with age, mostly.


Men develop bladder outflow problems because of enlargement of their prostate glands. Like any heavily used muscle, the muscles of their bladder walls thicken and their bladders lose their elastic youthful accommodating character and feel full with just a small fraction of what they once held without effort. They have to be emptied frequently.

Tell those men to drink liters of water a day and they will tell you ‘no’. They already get up once or twice a night. They already interrupt business meetings to void. More water is not on their agendas. And, they do not want more stones.

Prostate surgery has become a refined and efficient treatment, we tell them. Many surgeons demur: Not bad enough yet. Many patients, too.


As if by some divine logic they suffer the exact opposite dilemma. Childbirth, and perhaps other mysterious losses of pelvic muscle tone with age make their bladder control perilous. They empty them frequently, as men so.

The advice to drink more sounds reasonable and undoable in equal proportions. Surgery is plausible but perhaps less reliable than for men.

Men and Women with Diseases That Lower Urine Volume

Gastroenterological diseases that cause chronic diarrhea lower urine volume, and to raise it can be remarkably difficult. People with ileostomies are perhaps the most seriously affected, and those from whom a significant length of small bowel has had to be removed.

The Needed Urine Volumes are Remarkably Large

Obviously, Low Flow is a relative judgment. For people who do not make stones, the issue is generally meaningless. For most stone formers, the urine volumes I already provided are reasonable guides. But there are patients who need extremely large urine flows, so they are ‘Low Flows’ in a relative sense: They must achieve far beyond the usual and it has always been our responsibility to help.

Cystinuria is an obvious example. It can take 4, even 5 liters of urine daily to prevent formation of these stones. And the flow needs to be kept up overnight.

There are calcium stone formers we have seen who if they let up on fluids for even one day form disabling painful crystals that occur in showers.

These latter are probably deficient in some defenses against crystals that in most of us work well. The so-called inhibitors of crystallization are poorly understood, but all stone clinicians and researchers are convinced of their importance.

As Dr Bernhard Hess when working in Dr Coe’s laboratory said once “Urine is a mess, but it is an interesting mess.”

And it turns out that women and men seemingly differ in their inhibitors.

Some People Won’t Drink Enough Water

They Don’t Get Thirsty

There are those who are habituated to a low urine volume and never realize it until they are confronted with the numbers on the lab sheet.

“But, I drink when I am thirsty.”


The thirst mechanism is set low so that he/she is never thirsty. When the neurobiology of the thirst mechanism is explained, some traction may be gained in their minds so that the habit can be altered.

They Get Bloated

“I feel bloated when I drink more.” The cry of the slim who want to wear their pants very tight and even one pound more makes them feel bloated, fat.

They Don’t Have Time

Or the cry of those who are so intent on their work that they can’t interrupt it to drink or make the obligatory trip to the bathroom.

These can be intense people. One recently told us he begrudges himself time to cook – he lives alone – or shop, and even time to eat. His work is very important: He is a successful academic scientist.

They Forget

“I forget to drink.” There are people who forget to eat. Alas, I’m not one of them. Just so, there are people who forget to eat or drink, or there are people who when stressed stop eating and drinking. Many become so overwhelmed with their busy lives that the first thing they forget to do is to drink any fluids whatsoever. Whether this is a learned behavior or biology has not, to my knowledge, been studied.

Some Examples

This vigorous man volunteers as a referee for sports – he runs up and down the court in basketball games (very dehydrating), football, and baseball (not so dehydrating except in hot weather). He does this for maybe 4 games in a day, 5-7 days a week. He and his wife politely disagree about the number of games and the number of days – she more, he less. His stones worsened when he ‘retired’ and increased his refereeing greatly.

An executive whose work requires long and many meetings – “who knows what decisions would be made the instant I leave the meeting.” Fluids were off the table.

This neo-natal intensive care nurse could not bring fluids into the unit. It was and is a hospital rule. She works 10 hour shifts about 4 days a week, and retiring is not a possibility for her or her family. Likewise, this is her specialty and she has no intention of changing to another.

An energetic and brilliant lawyer loves the exhilaration and combat of litigation but reluctantly changed to research because she couldn’t stand the dehydration. “I cannot leave the courtroom without asking the judge and I can’t do that.” She is not as happy with her new career but is a lot happier since her stones no longer form.

This one person has a story that is almost commonplace. Daily she commutes to and from work. She can find no good bathrooms during the two hour commute each way so has to stop drinking hours before she leaves either home or work.

A lady with cystine stones who has been our patient for years. She goes to all her sons’ soccer games and has to stop drinking a few hours before hand because otherwise she would have to return home to use her own bathrooms. She wrinkled her nose in disgust at the notion of the porta potties at the game site.

What Did We Do?

There’s a frustration. We did do a lot of things, and we wrote them down. But all that writing is buried away because we never went back and wrote the paper. Some things may have appeared to work. Others surely did not. Memory is a fading thing.

Every case I just mentioned had some kind of workaround, and each one was some mix of medical care and social engineering.

You might say all we had was observation: No prospective randomized trials – and that is true. Also true, observations are the seedbed of trials. What seems to work is what you need to test. Each example seems unique. But I suspect there were general approaches hidden away in the particulars: We buried treasures, and they are buried still.

I know for some we prevailed, and for some we did not. It is as if I am telling the same tale over again. Without a paper, whatever we did might as well be lost, burned up in a fire.

Surely there are hints in our old records of the right and the wrong ways to obtain successful outcomes. Surely we would have found a few.

What Do We Do Now?

About what we always did, but we have someone new. Jill Harris does diet counseling for kidney stone patients from all over the world because she works online. When we have a problem, we often send patients her way. Here is her way.

How Would We Have Written The Paper?

As I have been writing this post, I muse on how to construct the file, for everything is in that step – you cannot analyse what you have not reduced to some consistent order.

The file is a table – all the stuff we think matters gathered together in a systematic way and susceptible of analysis using mathematical instruments.

This all sounds to technical, yet it is the beating heart of clinical research.

Did you know this already?

Such a mundane and yet essential business as getting urine volumes to rise, and yet so complicated because in the midst of life as lived. All that complexity must be signified in a table, somehow, or there is no making sense of it.

Thousands of chart entries, laboratory data, and all of it useless for insight until brought into one place, as numbers, or yesses and noes, or types of treatments.

We had thousands of encounters, recorded them, succeeded or not, and what we did is dust in the buried wood because we made no table. It is that simple, that plain.

What Would Have Been a Proper Table?

The style for this type of research is that patients are their own controls.

It is the change from their base conditions to their treatment conditions that matters, and how much has changed.

Is it enough?

If stone risk decreases and stones disappear it can be said to be enough.

What did we do to succeed or fail?

How Would I Have Made a Proper Table?

The Main Information

The usual research file that I made has each patient on one row.

Laboratory data are averaged for before treatment starts and for all the follow-up urines during treatment.

But, as I think about it, I would change this file to have three numbers during treatment: The first follow-up, the last follow-up, and the average.

Why Would this Technical Detail Matter?

I have noticed over the years that the first try to increase urine volume often doesn’t work. It may be we would find in analyzing the data that there are those who succeed the first time, and those who don’t.

Some never succeed and some raise their urine volume and keep it high for years, and new stones do not appear. This might be a clue to differences one might discover by having the first and last study separate.

The Other Details

The file would contain far more than the urine volume.

Many dates, from birth, to entry into the program, the first stone, our last contact with the patient. All the laboratory data go along with those urine volume numbers. So do clinical data such as numbers of stones, types of stones, surgeries and so forth.

Most of all, some code for what we did as a way of encouraging more urine volume.

This would have been difficult because much of the detail is written in the notes and I would have to get it back out into some kind of coding. That takes a lot of time.

What We Would Have When All this was Done

The file might have been 80 to 100 columns and over 4000 rows. Before the analyses could even be started, I would test the file for outliers, mistakes, duplications, really odd data that makes no sense.

The whole process of refining the data and then refining the analyses looking for patterns and testing ideas, constructing the figures and then writing the paper would usually take a year or more.

What Might We Have Found?

Exploring clinical data for me was always high adventure, seeing how my fellow hominids lived prior to their entry into our program and then seeing how stones go away, and how their lives have been improved, at least in this one area.

But always as I worked away with the statistical tests, I would be thinking of the patients whom this analyses would hopefully benefit – I would keep in the back of my mind the stories of those who had trouble drinking water, their faces and their voices informed the questions that I could ask statistically.

Is there a difference between men and women in urine volumes?

Is there a difference by age?

Is there a difference that correlated with anything else, such as urine calcium, or numbers of surgeries?

Is there a difference between men and women in raising their urine volumes?

If a patient achieves a high urine volume as a result of the fresh memories of a painful stone attack, does that high volume persist through years of follow-up? Or does that patient revert to the low volumes as they forget about the stones?

How well did we do? Did most of our patients raise their urine volumes?

How much.

Was the increase the main reason their supersaturations fell?

Did most of the low flows eventually stop making stones?

Did they perhaps tend to leave our practice because frustrated by our demands or the impossibility of doing what we recommended?

Which of my carefully coded approaches seemed most promising?

Could it be tried in a deliberate trial design?

Did it seem effective enough to warrant such effort and expense?

Why Would We Have Written the Paper

I have already said why in a scientific sense.

Did we succeed at all?

With whom?

Doing what?

How well?

With what effect on stones?

But I have not said why in a more humane sense, a more personal sense.

There are patients who come in and are crestfallen and utterly surprised to discover that their urine volume did not increase – “But I drank and drank and drank.” they protest. Their urine volume remains much too low for their safety, their stone risk much too high for safety.

The paper that was never written might not be of direct clinical help to patients who are at their wits end trying to drink more water. But maybe, if the paper said it took previous patients who seem much like you this many tries and this many months to achieve more safety from the use of water, the paper would indeed be of use to patients who are only trying to live their life and stay healthy.

It can be consoling for you as a patient to know you are not alone in struggling and failing to do something as seemingly simple as to drink more water, for it is simple only to those who never have to think about it, much less change the habits of a lifetime.

“That much water is disgusting. I get nauseous and can’t drink it.” I think this reaction is more common in the slim and fastidious, but we never wrote the paper so this is a mere intuition. As Jill Harris has written, changing the habit gradually will work better for most people. Adding a little something to make the beverage more interesting will also help.

Why Don’t I Write The Paper Now?

So why, you ask, don’t we do the work for this paper that haunts me, when I even know the questions that could be asked?

Why not take the time to do this important paper?

I suppose Ecclesiastes 3 (King James Version) offers the answer:

To every thing there is a season, and a time to every purpose under the heaven

11 Responses to “THE LOW FLOWS”

  1. B Harris

    I urinate sand like particles. They are very fine and when I touch them they disintegrate. Some can be as large as 2mm. I had the particles sent off to a lab and they were 95% Calcium Phosphate and 5% Oxalate. This happens about 3/4 times per year. I always assumed that these particles were larger stones somehow breaking up? I do drink a lot of water but I have no clue what is going on. Any ideas?

  2. Cynthia Tucker RN


    I have a 7 yr old boy with massive amounts of Calcium Phosphate is his urine. It actually looks like coffee creamer at times when he urinates. We noticed it after the onset of precocious puberty. His urine is always concentrated, low ph, with blood. They want to try Potassium citrate, but he doesn’t drink enough water and stays in a constant dehydrated state. Thoughts?

    • Fredric Coe, MD

      Hi Cynthia, My guess is massive hypercalciuria – check the 24 hour urine stone panel. Possibly it is renal tubular acidosis. Potassium citrate is not so good if it raises urine pH. He needs a diagnosis. Let me know. Best, Fred

  3. Fae

    I have struggled with mixed incontinence since I was a child, after having 3 children it has been manageable but aggravated by increased fluid intake. I formed my first stone in 2013, 7-8mm. With two ESWL that stone was eliminated in January of this year. I increased my fluid intake and 24 hour urine in June showed glowing results. less than 3 months later I have a new 4mm stone. I am at a loss since I am really between a rock and constant trips to the toilet these days.

    • Fredric Coe, MD

      Dear Fae, High fluids are a cornerstone of prevention but not necessarily sufficient. The key issues for you are two: What kind of stones do you form – the crystals in them; What is abnormal in your urine chemistries besides urine volume itself? Real prevention is to lower supersaturation for the crystals in the stones you actually form, and this requires you know both the crystals and the supersaturations, the latter from the 24 hour urines. What went wrong with you – if indeed this is really a new stone – is that the supersaturation for the relevant crystals was not low enough. A pitfall of fluid intake is timing – high fluids need to protect you day and night but 24 hour urines are the overall average of the day and night. You need to see to it fluids remain high all the time. Alternatively, if other risk factors in urine can be corrected, you do not depend on fluids so much and can make life less onerous. My remark about ‘really a new stone’ refers to how certain it is that there were no stones in the kidneys after SWL. Was there just a simple flat plate x ray? I noticed it took 2 SWL, and wonder if even the second one was sufficient. Whatever, you can have a good chance at being stone free with the steps I have mentioned. The site has multiple articles about how fluids need to be used, about citrate and the problem of high urine calcium. I hope they help point you in the best direction. Regards, Fred Coe

  4. Steve F

    Hi. I had my first very noticeable stone at age 21. I just had another one recently at age 37. Both were around 3-4mm. My recent ultrasound shows more stones — two 3mm in one kidney and one in the other (and other possible small stones). I remember the similar sensations from a young age (5 or 6) but those two were quite memorable.

    Anyway… I have ALWAYS been a “low flow”. I have always sweat more than I urinate. Many times, even a bit warm and not hot, and I’m sweating. I jokingly tell my wife that this is how I urinate — through my skin. If I am hiking, I’m drinking quite a bit of water, and guess what? I’m not urinating. The more I drink, the more I sweat. I can destroy a pillow in a matter of weeks with sweat. This has been my entire life and seems to be a family thing.

    This is the case that you do NOT describe and was wondering if there was an answer other than “drink more”. While in general, I COULD increase my water intake, many times, I’ll just sweat it out. 🙂


  5. Jill

    Hi Trish,

    To answer your question about black tea, yes! It is very high in oxalate and could be increasing your kidney stone risk. We will be writing about oxalate in the very near future!

    Best, Jill

  6. Patricia McClain

    Most of the time I do pretty well drinking water. These are all ideas about drinking more water.

    I might add there are flavored waters out there and I don’t think they have added salts, sugars etc. for some people that may be an option/idea. Kidney stoners would need to check out what is available in their local area.. The ones offered at my local store did not seem expensive. Walmart had carried these in the past for a low price. In some parts of the US there may be better stores than that. Also Whole Foods is an expensive store. It was mentioned for buying a particular kind of lemonade. I would try Trader Joe’s for that, if possible.

    You can add a slice of a citrus fruit to flavor water and then squeeze it in the water… also many spas offer cucumber water… water that has had thin sliced cucumbers added to it. I don’t know how long they take to flavor the water. You can use a thin slicing blade on a good food processor to cut up cucumbers. Basically this is an infusion. If you are going to add citrus peel to your water, it needs to be washed off with some kind of soap. I was told a mild white vinegar solution helped in reducing bacteria.

    For anyone who spends 4 hours or more at their home it might be helpful to keep a pitcher of water in the refrigerator… there are some that have measuring marks on them. Also, if that doesn’t work bottled water could be a good option. Costco and my local grocery store which is owned by Kroger’s have good prices. Some people will drink cold water but not room temperature water.. others may find ice water is harder to drink. Also some people find there water does not taste good… it is possible to buy a pitcher with a water filter on it… or filters for your kitchen faucet. Not everyone needs a $2000+ refrigerator with filtered water and ice.

    Now I would like to slightly stray from the water topic: Does anyone else have a hard time swallowing their potassium citrate? I have a hard time swallowing (taking) my potassium citrate pills… they get stuck in my throat and I never know how much water it will take to get 3… 1080 mg pills down 2 times a day. The pills are very soft with no score so I can’t split them in two. I can use 12 ounces to over 24 ounces to swallow them. I also had to have a glass with a thin lip on it… the normal double walled plastic glasses (so they won’t sweat) glasses I drink out of don’t work… I end getting pills stuck in my throat.

    I accidently discovered one day that drinking out of a water bottle alleviates all the problems… I can get them down with about 1 cup of water or 1/2 of a 16 ounce water bottle.

    I know drinking water is a challenge for some people, some people don’t seem to get thirsty often. I wonder if there is a genetic component to that. My husband grew up in the Arizona desert and drinks water like a tortoise. I was also told his father did that. My first urologist said if I had not been a water drinker, I would have been much sicker than I was.

    From age 13 to age 19 I had a colic episode once a year, in March or April. A couple of those times, I passed the stones at home and did not need any surgical intervention.

    My worst problem in the water department is: I drink black iced tea and water daily. I don’t know how bad the tea is… I have green teas and herbal teas also… but I need some caffeine. Green tea has about 1/3 the caffeine of black tea. The tea is straight… no lemon or any kind of sweeteners. I rarely have juice, I don’t like regular milk… I use soy milk on cereal. I also take iced tea with me when I drive in my car… I can take water too but, it is hard to carry 2 drinks, a purse etc to a car. Even if I leave the house for 5 minutes, I have to have a drink.

    Does anyone else have a problem because they drink black tea? What have you been told by your doctors? Has anyone ever been put on the low oxalate diet?



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