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.

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

  1. Emily

    Hello my mother is 55 years old and just got her gfr back and it is 49 and creatine was 1.24. She has lupus but she also has a 1mm kidney stone. She has been having lower back pain recently. 3 months ago her creatine was normal and her gfr was 86. How did it drop so fast? Should I be worried?

    Reply
    • Fredric L Coe, MD

      Hi Emily, This reduced kidney function is most likely from her Lupus or some other cause than her 1 mm stone unless the stone is obstructing a kidney. The matter is of high importance and I do not have enough information to make any useful statement except that her physicians need to figure out the cause right away and make some appropriate treatment plan. Regards, Fred Coe

      Reply
  2. Bobbye Casner

    I’m a 70 year old female with a 1.2 cm and an 8mm kidney stones. My last blood test showed an elevated bun/creating ratio. In fact, every blood test I have always has an elevated ratio for years. Should these stones be surgically removed or left alone until they present with a problem? I also have been treated with high blood pressure for 19 years. I have moderate peripheral neuropathy and have been experiencing very low body temperature when up doing light housework, such as 95.5 or lower . Any advice would be greatly appreciated.

    Reply
    • Fredric L Coe, MD

      Hi Bobbye, Sorry to be so late. High BUN to creatinine ratios usually reflect either increase in protein breakdown to urea – common cause is steroid use or high protein diet, or diuretics that favor urea reabsorption – perhaps a blood pressure treatment. Low body temperatures can reflect hypothyroidism and that can also possibly raise the BUN/creatinine ratio, but I doubt that is your issue. I would guess it is a diuretic. As for symptomless non obstructing stones, in general I leave them alone but your urologist needs to make the decision as I have not seen your CT scans and am not in a position to make a recommendation for you. Regards, Fred Coe

      Reply
  3. Dias

    Hi Doctor!
    I am 22 and have been having kidney stones for about 6 to 7 years. I usually have about 2 to 3 stones on each of about 3 mm to 4 mm in size every time I take an ultrasound. I had taken homeopathy medicine and it reduced the frequency of pain and number of stones. However, once stopped my body keep’s producing stones.
    Does having kidney stones for several years cause damage to the kidney? Am I in risk of CKD?
    Also with regards to the COVID-19 virus, is my condition considered as an “underlying disease” and therefore worsen the risks of fighting the virus?

    Your advice on this will be greatly appreciated. Much thanks!

    Kind Regards,
    Dias

    Reply
    • Fredric L Coe

      Hi Dias, Kidney stones can gradually damage kidneys but usually not so early in life. I would suggest you consider regular medical prevention – here is a good article to consider. As for Covid, you are not at high risk unless your kidney function is importantly reduced, and your physicians can tell that from routine blood tests. Regards, Fred Coe

      Reply
      • Dias

        Thank you Doctor for your reply and information. I will keep that in mind.
        Could there be a patient who has slightly lowered kidney function to significantly lowered kidney function, that show no to less symptoms?
        I am not able to get any tests done, as doctors recommend that I stay away from hospitals unless extremely urgent. Therefore, I am also not going to work these days.

        Thanks & Regards

        Reply
        • Fredric L Coe, MD

          Hi Dias, Mild reductions of kidney function cause no symptoms and if present the matter can wait until the epidemic is over. Regards, Fred Coe

          Reply
          • Dias

            Once again, thank you very much for your time and information! 🙂
            Tc

            Reply
  4. Hi i am 35 years old. How can i decrease my high creatinine level which is 1.26? After using PNL procedure to remove kedney stone, still there is stent in my ureter for three months.

    Happy to see you

    Reply
    • Fredric L Coe

      Hi, I presume your serum creatinine has risen, and assume that is from the PNL. The main thing is for your urologist to be sure no obstruction remains. Possibly kidney function will improve. But if there is obstruction, a kidney can be damaged or even lost. So, be sure your urologist is maintaining normal drainage. Regards, Fred Coe

      Reply
  5. Subodh Raya

    Hi, My dad is 68 years and From Ultrasound report, it has impression of multiple left distal ureteric calculi near bladder with Hydroureteronephrosis, Left renal cysts, Irregular outline of right kidney likely due to scarring/previous infection, CMD maintained in both kidney; mild edematous parenchyma of left kidney. My dad’s creatinine level fluctuates from the ranges 1.6 to 2.2 over the two months. Sometimes, it had 3.1 and retreat into 2.1. Still it has been consistency in around 2.0, 2.1 and 2.2. Is there any possibility of normal creatinine level after removing stones

    Reply
    • Fredric L Coe

      Hi Subodh, It sounds like the left kidney is obstructed and has been damaged by obstruction. Likewise he has some scarring of his right kidney and that accounts for serious reduction of overall kidney function. Removal of the obstructing stones is critical. I do not think kidney function will return to normal so much as it may stabilize. The real risk is progression to kidney failure with need for dialysis. Prevention of more stones is crucial, so you need to know what the stones are made of and why they form. Regards, Fred Coe

      Reply
  6. Dr Pankaj Bohra

    Hi Dr ,
    I had left ureteric stone 12 mm in 2007 which was removed by a Urologist but I still have 6 mm stone in my right ureter which is non obstructive, which was 4 mm till 3 years back.
    My creatinine is around 1.2 and I have increased frequency of Urine. I am a non diabetic , Cholesterol 280 and eGFR was 81 three years back.
    What should I do , I am worried ?
    I am a Pediatrician FYI.

    Regards,

    Dr Pankaj Bohra

    Reply
    • Fredric L Coe

      Dear Dr. Bohra, I presume there is no dilation of the upper tract but the stone is growing in the ureter. I would think simple removal via URS with laser would be the best idea if your surgeon think that is practical – as the stone grows it may obstruct, and without pain. You do not mention the stone location but urinary frequency suggests it is at or near the UV junction. The reduced eGFR is hard to assess as I do not know your age, but I do not think it is from the stone if it is really not obstructing. Regards, Fred

      Reply
  7. Rose Parise

    Hi
    I was discharged from the hospital. I have a 1.5cm obstructing kidney stone L ureter. The urologist feels it has been there for a while. I had grade 4 hydronephrosis. I had a nuclear renal scan that showed 13% functioning of the L kidney and 87% of the R. I had no pain just became very ill with chills, fever, vomiting and some L sided abdominal cramping.
    To make a long story short. My creatinine is back to normal but my Urologist feels that the kidney was very damaged and the wall of the kidney is very thin. I currently have the nephrostomy tube and have a follow up appointment on monday. Dr. has been recommending that I have a nephrectomy. He said if I chose to keep the kidney I may end up with chronic infections because of the poor function.
    Does kidney function improve over time….what are your thoughts?
    Thank you

    Reply
  8. Stavros Michailidis

    Could there be any relationship between breathing and kidney stone formation? For example, could deeper, slower breathing affect PH levels, Citrate levels, etc? I’m sure there is little research on this but could you see a mechanism that would connect the two? Thanks for considering my “not-so-in-the-box-idea”.

    Reply
    • Fredric L Coe

      Hi Stavros, altering acid base status by increased or decreased CO2 clearance – what you suggest – can have little long term effects on urine pH because the kidneys will compensate. It is also not a good idea, so far as I can tell. As an example, during pregnancy respiratory CO2 clearance rises, but overall renal bicarbonate handling comes into a new relationship with blood CO2 and bicarbonate and urine pH can reflect food conditions as always. Regards, Fred Coe

      Reply
  9. Charlotte Fleet

    Thank you for explaining that nephrons are complete and complex structures that begin by filtering a clear solution from the blood plasma. My husband’s mom has been struggling with some kidney issues. I think they should look into a good nephrology treatment clinic that can help them know which treatment is the best for her.

    Reply
    • Fredric L Coe

      Hi Charlotte, I would agree that with kidney issues your mother in law would benefit from nephrological care. Your comment is linked to a commercial site for kidney physicians, and I ban such on this university site, but given your apparent real issues have let the comment stay. I have little regard for nephrology practices that attempt to put their name up on sites as spam, but assume that is not the case here. Regards, Fred Coe

      Reply
  10. Breanna Smith

    Hi! I am 21 years old and have at least 5 kidney stones in my kidney. I’m in really bad pain and my urologist said that there is nothing he can do. I also have swelling in my back where my kidneys are located. I dont really know what to do at this point..

    Reply
    • Fredric L Coe

      Hi Breanna, I presume your stones are not obstructing, and that you are part of a large group of people with non obstructing stones and pain. Trials are lacking about whether surgical removal of the stones will help reduce pain. Prevention of more stones and more crystals may well help, however, and here is a good article about what to do. regards, Fred Coe

      Reply

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