Kidney Stones, Kidney Function, Kidney Disease

Glomerular filtration is the main life sustaining kidney function, and kidney stones can cause enough damage to lower it. Usually the reduction is very modest, but sometimes stones can cause kidney failure. This means, like all diseases, stones are best prevented as early and as completely as possible.

This ‘just the facts’ version tells about what filtration is, how physicians measure it, how much kidney stones lower it, and how often that occurs.

Two longer articles give the details. One is comprehensive. The other focuses on only kidney disease, but is long.

Much of this text is redacted from the other two articles. I left out pictures, data, and links to PubMed to emphasize the main points.

The featured painting is by You Si 游思 (b. 1954), based in Shanghai, China. He is the son of two artists who lived through the cultural revolution and paints in new ways. I think his work is gorgeous but could not find a serious biography or critical study, or any museums that show his work.

What Filtration Is

Our two kidneys are each made up of about one million nephron units. A nephron is a complete and complex structure that begins its function by filtering from blood plasma a clear solution of water and small molecules. That filtrate enters the long loopy tubule of the nephron that reabsorbs a vast fraction of water and salts back into the blood leaving behind only that destined for export out of the body.

The glomerulus, a tuft of capillaries nestled in a tiny cup that drains into its tubule, performs this filtration. So we name it glomerular filtration rate, or GFR.

Blood flow and pressure from the heart drive filtration, but kidneys can regulate its rate. The cells that line the tubules regulate what fractions of innumerable individual salts and small molecules are taken back or let go into the urine.

Filtration Keeps Us Alive

Filtration rids the blood plasma of metabolic wastes, like oxalate, and permits us to excrete the extra water, salt, and all other materials we might eat or drink every day. Without filtration we need dialysis or transplantation to continue living. So this kidney function stands above all the others. When physicians speak of kidney function, they mean, and measure, filtration.

Filtration and Kidney Stones

Kidneys filter copious volumes of water and small molecules – like calcium, oxalate, citrate, phosphate, uric acid, sodium – hundreds of distinct materials. They then return most of this flood – 100 to 200 liters a day of water alone – back into the blood keeping behind only what they destine for export as urine.

Because kidneys filter such vast amounts, very subtle variations in what they take back into blood can load the urine with stone forming salts like calcium and oxalate, and cause stones. In other words, stones arise in significant measure because of subtle imbalances between filtration and reabsorption of key materials like calcium, oxalate, citrate, and water itself.

The filtering system, though powerful, is delicate. Through obstruction, infection, loss of one kidney, or surgical trauma stones can injure it. Such injuries reduce the ability of kidneys to protect the body, and when severe can lead to chronic kidney disease and even need for dialysis or transplantation.

How We Measure Glomerular Filtration

Serum Creatinine

Muscles make creatinine steadily and send it into the blood. Like almost all small molecules, kidneys filter it. Serum creatinine therefore reflects the balance between muscle production and filtration. When filtration falls serum creatinine rises. It is like your golf score – bad day, higher score. Serum creatinine gauges filtration adequately enough for clinical practice. But because kidneys not only filter creatinine but also secrete it from blood into urine, creatinine overestimates true filtration.

eGFR

To get a better estimate, scientists compared serum creatinine to true GFR in reasonably large populations and calculated the best fit between them using regression techniques. The resulting regression equation gives estimated GFR, or eGFR, from serum creatinine, age, sex, and race. This highly derived index dominates medical practice. When physicians speak of reduced kidney function they mean reduced eGFR.

Kidney Function in  Stone Formers

Average Function is modestly reduced

Our Own Patients

In our own patients, we found that stone formers have lower kidney function than normal people. The common idiopathic calcium stone formers are just slightly low. Likewise for those with primary hyperparathyroidism. But kidney function is reduced by about 20% in people who make stones because of bowel disease or diseases like renal tubular acidosis or cystinuria. Uric acid and struvite stone formers have even greater reductions.

US Health Surveys

The national NHANES data survey results showed modestly reduced kidney function in overweight people who had a history of stones. Women who formed stones had increased risk for serious chronic kidney disease, and even dialysis.

Olmsted County 

This community uses Mayo Clinic for care so records are very complete. A history of kidney stones increased risk of CKD and eventual dialysis.

Large Reviews

Two extensive reviews of all published studies – not just the few I mentioned – concluded that where ever looked for, stone forming raised risk of high blood pressure, serious chronic kidney disease, and even dialysis.

Though Increased, Kidney Disease Rates are Not High

Stones raise the risk of serious kidney disease from the very low levels in the general population to higher though still low levels. The vast majority of stone formers do well and never have problems that require special kidney care. Only rarely do stone formers need dialysis. But they can come to need such care more frequently than people who never formed a stone.

The message is obvious. Stone recurrence should be minimized through prevention efforts. Physicians who practice stone prevention need to measure eGFR appropriately, and if it begins to fall take proper steps to mitigate the causes of that fall.

Obstruction from stones always needs prompt, skilled, urological care that minimizes risk and trauma from surgery. Because silent obstruction can destroy a kidney, any symptoms that suggest new stone passage deserve urological attention.

High Blood Pressure

The NHANES and Olmsted County data show that a history of stones raises risk of elevated blood pressure. Loss of kidney function, even subtle, could raise blood pressure, and increased blood pressure can harm kidneys and reduce GFR. Unlike significant kidney disease, high blood pressure is easily treated to prevent strokes, heart disease, and kidney failure. But high blood pressure commonly escapes diagnosis and adequate treatment.

This means kidney stone prevention clinics are high blood pressure clinics, or at least a common place where high blood pressure can be first detected. All stone formers need to know their blood pressure and seek care if it is elevated.

Bottom Line

Stones are a painful and recurrent chronic disease that kidneys generally tolerate with at most a modest amount of injury and function loss. But compared to people without stones, those who make them have measurably increased risk of high blood pressure and loss of kidney function. Years of study have made clear that this disease demands attentive treatments aimed at prevention, and that surgeons who manage stones do everything possible to preserve kidney tissue.

92 Responses to “Kidney Stones, Kidney Function, Kidney Disease”

  1. Joanne

    Hello. My father is being investigated for kidney disease. His GFR is 15. His CC is 333 and his urea is 20. He and my mother are going away for 2 weeks and I am incredibly concerned. His nephrologist has said he can go and we will do further investigation when he gets back. What would your advice be? Do I trust the nephrologist or my nurse instincts. Any help would be gracefully received. Regards. Jo

    Reply
    • Frederic L Coe

      Hi Joanne, Your father has very significant kidney disease. I suspect his nephrologist is correct and his trip will do no harm. So long as serum potassium and bicarbonate are not too high or low, respectively, and kidney function has been stable over time, a wait is not necessarily a risk. I would trust him/her. Fred

      Reply
  2. Hether

    I am a 41 year old female and I experienced my first kidney stone episode last May. I had a 5mm stone I was trying to pass which is what landed me in the ER. From the visit and a follow up with a urologist it was found that I had 3 other stones all in my left kidney and they were quite large. Too large for lithotripsy. After 4 lithotripsies, a ureteroscopy and a 5 day hospital stay from a kidney obstruction (worse pain I ever felt), it was finally determined I was stone free. 3 months later at my follow up X-ray and ultrasound I was advised I had a couple new stones also in my left kidney, but they are too small at this point for active treatment. I’ve gotten no explanation on the reason I am developing stones so fast or so many of them. I also suffer from high blood pressure and have for years.. the last year however, I have not been able to get it down into a “normal” range even with medication. My GFR has never been tested as far as I know. At this point though I’m wondering if it would be beneficial of seeking out a nephrologist. Am I at higher risk of kidney disease? Should I be concerned ?

    Reply
  3. Melissa

    I cannot tell you how much this article means to me, even if I still feel a little helpless. I am a 34 year old female who has had a history of chronic stones since I was 22. I have had one lithotripsy but the rest have passed. The past 5 years my GFR has been quickly decreasing and started well into the 110-112 range to now 86-84. Despite this, my creatinine levels are “within normal range” and since my GFR is still above 60, my primary care and urologist are not concerned. I know they are just going to wait until it drops to actually try and consider preventative measures. I eat very healthy, exercise regularly and take care of myself. I wish other physicians saw the correlation and actually were proactive instead of reactive. I was just told chronic stones “just happen” and since I am still within normal ranges I am fine. Yet according to the kidney foundation I have a GFR rate of someone in their 60’s.

    Reply
    • Fredric Coe, MD

      Hi Melissa, Falling eGFR is not ideal and the cause matters. Stones are themselves a problem for kidneys, they do not ‘just happen’ and need prevention. Here is a good place to start. Be sure about even slight obstruction from stones, and about your blood pressure. Perhaps a nephrologist might be helpful. I have no great enthusiasm for waiting to see what happens. Regards, Fred Coe

      Reply
  4. Hemanth

    My 3 years boy baby had blood in urine all the reports were normal doctor said they dont know the reason she told only urine citrate was low

    Reply
  5. Donya

    Hi
    My husband has high creatinine level and rare oxalate and blood in his urine, is that a sign of kidney stone? Or something else might be the reason ?

    Reply
    • Fredric Coe, MD

      Hi Donya, high creatinine and oxalate crystals may mean primary hyperoxaluria, a very dangerous cause of kidney failure. His physicians need to be sure it is not the cause of his kidney failure. Please mention this to them. Regards, Fred Coe

      Reply
  6. yogesh arora

    Hi,
    My sister in law has a stone of 11 mm and gfr 10 which improved to 18 in 15 days after PNC now a doctor is suggesting removal while other is saying gfr has improved so this kidney can be saved please suggest. Patient is not diabetic and hypertensive.

    Reply
    • Fredric Coe, MD

      Hi Yogesh, Given a gfr of 10 it means that neither kidney functions well. The two stones could not cause such dangerous kidney disease unless they obstructed both kidneys. Alternatively she may have a cause of stones that also causes kidney failure. This is a very urgent and potentially dangerous situation, and only her physicians can really figure it all out. But certainly one can say any obstruction needs to be repaired. A GFR of 10 is near to needing dialysis. Regards, Fred Coe

      Reply
  7. Paula

    My husband had his left kidney blocked by a stone. His eFGR was at 18. Isnthis something to be eon ended about? He’s a type 1 diabetic and there was talk that his right kidney had failed already. Thank you

    Reply
    • Fredric Coe, MD

      Hi Paula, With only one kidney working well, obstructing the good one causes a very serious acute kidney failure. I am sure your urologist has already seen to proper drainage on the obstructed side and his eGFR is back up to normal. Prevention of more stones is crucial, and rapid treatment of any other stone events likewise. Uric acid stones are common in diabetics, and always immediately curable, so be sure about the stone type and about prevention. Regards, Fred Coe

      Reply
      • Paula

        Thank you. He’s in stage 3 B CKF already. I’ve placed a call regarding the type. Our care isn’t that’s great because it the VA and they’re extremely busy.
        Sorry for the typos. I can’t see the screen!

        Reply
        • Susan Wade

          I went from stage 4 kidney failure in a 7 day span, it was 25 gfr too 31 gfr. Is it normal to fluctuate somewhat and if so, what would cause that that to happen?

          Reply
          • Fredric Coe, MD

            Hi SUsan, These are serious numbers. Be sure your physician knows why your kidney function is reduced and is taking all possible care of you in regard to it. Fluctuations in kidney function can occur from diet or drugs. Your physician will know in your specific case. I want to emphasise the importance of your receiving skilled renal care. Regards, Fred Coe

            Reply
            • Deborah Helms

              Hi my name is Deborah…I have had two kidney stones sent off for the stand bloodwork that came back…this is the 3rd time my lipase has been elevated and the stones came back inconclusive because they contained cellular material. Please advise me on the next steps I should take!

              Thanks,
              Deborah Helms

              Reply
  8. Dawn

    My 5yr old daughter was found to have kidney stones this past summer. One was 5mm in the right kidney and a smaller one in the left. We saw a urologist and a nephrologist. The nephrologist ordered a 24hr urine catch which showed severely low citrate levels (71). Started her on potassium citrate. She wanted to wait over 6mo to retest. I wasn’t comfortable with that or with asking her to retest so our primary sent off another 24hr test. Ended up testing for the wrong thing…oxalate numbers. Her oxalates were in the normal range, but her oxalic acid with creatinine was substantially high….102.6. We have an appointment on Monday to discuss this finding with our nephrologist. But in the meantime, what can you tell me about this number? Does it indicate her kidneys are struggling? Should we repeat ultrasound for new stones? Thank you!

    Reply
    • Fredric Coe, MD

      Hi Dawn, The low citrate needs to be matched against reliable normal ranges for a 5 year old person. Likewise the ratio of urine oxalate to urine creatinine. A low citrate means one thing, high oxalate another. It is crucial your nephrologist sort this out and I am sure s/he will do so. Of the two, the oxalate is certainly the more serious issue. Regards, Fred Coe

      Reply
      • Dawn

        Thank you for your reply! My next question is one I have not been able to find anywhere: what does high oxalic acid/creatinine mean?? Not the same as high oxalate correct? So add the creatinine in, what does it I dictate. All the levels we have been given I assume are ranges for a child. The nephrologist we see is pediatric so the citrate was. The oxalic acid/ creatinine I am not sure.

        Reply
        • Fredric Coe, MD

          Hi Dawn, Total urine oxalate excretion, for example in mg/day, is in part a function of size. Small adults will have less than large ones. For children, who are smaller than adults, one needs to normalize excretion by something to correct for size. Creatinine is made by muscle cells, so the amount scales roughly to lean body mass. If you divide total urine oxalate by total creatinine in the same sample you get a ratio of creatinine in = let us say – mg/gm creatinine. A typical adult will have perhaps 40 mg of creatinine per day in the urine with 1.5 gm of creatinine, or 40/1.5 = 26.6 mg/gm; so the value in your child at about 100 seems high. But children are really not small adults, so one needs to compare that value against pediatric normals. Your physician does this and interprets the result. Regards, Fred Coe

          Reply
      • Dawn

        High oxalic acid is not the same as high oxalic acid with creatinine, right? What does this indicate…the acid with creatinine? Thank you for replying!

        Reply
  9. Uch

    My husband is 45 years old and has kidney stone measuring 7mm. Most recent eGFR is 55. In 60s when adjusted for ethnicity. He also has juvenile hypertension (16 years) which has been kept under control until recently. His BP won’t come despite increase dosage of drugs. Could kidney stones by part of the cause of resistant hypertension?

    Reply
    • Fredric Coe, MD

      Hi Uch, Your husband has reduced kidney function and high blood pressure and a stone. He needs special evaluation because he may have one of the hereditary diseases that can cause both. Dent disease is one such. I would suggest evaluation at a university center given the potential difficulties. His condition can be diagnosed and treated, of course, but not without a high level of specialized skill. Regards, Fred Coe

      Reply
  10. Mohammed muktar

    Hello Dr. my regard to you.
    I m 36 years old male and I m having problem with my kidney filtration since 2015 to date. Sometimes my creatinine,Urea and Uric acid are raising. The must highest level it reach is creatinine 242mmol,uric acid 502mmol,and urea 9mmol.but no stone was found. what can I do?and is it a serious case?

    Reply
    • Fredric Coe, MD

      Hi Mohammed, You appear to have kidney disease and not due to stones. This is outside the purview of my site. I would be concerned and consult a nephrologist, as this kind of specialist focuses on primary kidney diseases. I would do this sooner than later, so as to preserve what function you can. Regards, Fred Coe

      Reply

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