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.

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

  1. Bill

    Dr. Coe, Thank you for your very informative articles. I am a 54 yr old male, and had my first stone at age 26. Five years ago, I started taking verapamil to prevent headaches. In the past 18 months, I have been passing many larger (4-6 mm), smooth stones. Do you think the verapamil may be causing them, or may actually be helping? Info I have seen on the internet is very confusing. Thank you.

    Reply
  2. Jay

    I’m a 47 year old female and found out I had a 4mm kidney stone when getting an ultrasound as just check up, nothing specific. The stone has not moved in 3 years. For the past 2 years my eGFR was at 100. This year during my annual blood test, my eGFR came back as 60 and my creatinine is at 1.097. I haven’t noticed any major issues in health, except 3 days before the blood test I pulled a back muscle and two days before the test I took an Aleve. I am now worried I have Stage 3 kidney disease. Is it possible that the stone has suddenly causing issues?

    Reply
    • Fredric L Coe, MD

      Hi Jay, I would repeat the test. NSAIDS can reduce renal function reversibly as part of their normal action. If the increase in creatinine is persistent it warrants consultation with a nephrologist. The US is interesting – what were they looking for??? Regards, Fred Coe

      Reply
  3. Poonam

    I have right kidney stone since 1999. 1999 it was operated with lathrotopics methods. Since 2009 I could not find any issue . In 2009 again it started painting . This time it was operated with PCNl method . Next 9 year (since 2018) I was not having pain. But again it started at mid of 2018. In July I had operated with stent ..as doctor told me that pain was not happening due to stone. Stent was removed after 40 days . Now i have lots of pain . I am taking pain killers. My right kidney GFR shows only 6.71. doctor gave me two options ..1. nephrotomy 2. Stone removal and do the follow-up .kindly advise me what should I do now

    Reply
    • Fredric L Coe, MD

      Hi Poonam, It sounds like your right kidney was damaged by stones and the inevitable effects of surgeries, and is no longer functioning well. Removal is a reasonable option. It possible I would suggest a second opinion at a specialized center just to be sure the kidney cannot be salvaged. Regards, Fred Coe

      Reply
  4. Saad

    My father’s age is 47.his serum creatinine level is 2.1 and renal stone 13mm .what i have to do next? Is there any problem?

    Reply
  5. Adrian Howard

    I am 37 years old and I was diagnosed with CKD Stage 3 April 2020. My eGFR was about 54 found out in October 2020 that that I have a kidney stone in both kidneys. I had to go to the emergency room in November as my blood pressure rose to 168 over 106 and a eGFR of 40. Could the stones be getting bigger causing more obstruction or could I have already had kidney disease prior to the renal stones?

    Reply
  6. mary t

    Hi my mom had 4 mm kidney stone left proximal ureter..had mild hydronephrosis at time of diagnosis 5-7 days after it passed ( or we think it did , my mom felt the pain move down ).. we redrew blood gfr was 38 creat 1.5 bun normal . Can my mom gfr get back to normal .. she was normal before this stone . I’m heartbroken

    Reply
    • Fredric L Coe, MD

      Hi Mary t, Obstruction lowers kidney function, so I would hope with time the kidney will improve. My question is whether the stone passed or not? Is the kidney still obstructed. Her physician can tell, and fix things if needed. Regards, Fred Coe

      Reply
  7. Lilith

    Can eGFR fluctuate? In the past I’ve been 101-117. September 2020 i was 117 and now my recent results taken 2 days ago show im at 99. I do have stone pain and ive had stones many times in the past but I’ve never seen it lower my eGFR.

    Reply
  8. susan

    I has a stone block my left ureter with some additional stone up high. I had a stent and lithotripsy and the obstructing stoned is mostly gone. Need another lithotripsy for remaining stones. I have a staghorn stone in my right kidney that will be taken out through my back when we are done with the let kidney. bun 31, creat2.28 and egr27 before the procedure. 4 weeks after procedure little improvement, do i have kidney disease or failure and how much improvement should i hope for

    Reply
    • Fredric L Coe, MD

      Hi Susan, I suspect that your large stones plus perhaps infection have caused some kidney damage. It is important for you to have a nephrologist as part of your medical team, and strongly suggest you arrange for that as soon as possible. That kind of physician is ideally trained to help preserve your kidney function. Regards, Fred Coe

      Reply
  9. Gayle Chizzik

    What about a calcium stone 8mm non obstructive causing pain with a GFR of 44… taken 3 times in. 55, 45, 44. Could it improve GFR?

    Reply
    • Fredric L Coe, MD

      Hi Gayle, You seem to have reduced eGFR yet stones are not obstructing. The reduced eGFR is a worry and given stones obstruction an obvious cause. I would be sure your kidney(s) are not obstructed. If stones are not the cause of the low eGFR something else is and your physicians need to figure out what that is and try to correct things. Regards, Fred Coe

      Reply
  10. Melissa

    I would like to know who painted this kidney art at the top of the page?

    Reply
    • Fredric L Coe, MD

      The work is by a Chinese artist. Details are at the beginning of the article along with a link to his site. Fred

      Reply

Leave a Reply