Kidney Stone Update 2021

Andrew Siegel MD 11/20/2021

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Kidney stones are a common affliction, 10% of Americans having experienced their misery. They can cause excruciating pain, on par with the most painful human experiences– childbirth, fractured bones, acute gout attacks, and impaired blood flow to organs.   The good news is that most stones will pass spontaneously without the necessity for surgical intervention. The other welcome news is that if surgery is required, it is minimally invasive—open surgery for kidney stones has gone by the wayside.

Typical appearance of a patient with renal colic;, CC BY-SA 4.0, via Wikimedia Commons

Why Stones Form

Kidney stones form when minerals normally dissolved in the urine crystallize into solid particles. They begin as a tiny “grain” that grows because the stone is bathed in mineral-rich urine that laminates mineral deposits on the surface of the grain. This crystal formation often occurs during periods of dehydration, typically prompted by summer heat, exercise, saunas, hot yoga, diarrhea, vomiting, bowel prep for colonoscopy, etc. Another major culprit is excess Vitamin C, which is converted into oxalate, one of the components of calcium oxalate stones, the most common stone variety.  Vitamin C is not stored in the body and any excess ends up in the urine in the form of oxalate. Other stone promoting factors are excessive dietary protein, fat and sodium intake, inflammatory bowel disease, and previous intestinal surgery.  Urinary infections with a certain type of bacteria (Proteus) can promote stone formation. Parathyroid gland issues and high serum calcium levels increase one’s risk. Some stones have a genetic/familial basis.

Types of Stones

There are numerous types of kidney stones, with calcium oxalate stones accounting for the majority.  Other stones types include uric acid, struvite (infection stones), and cystine stones. Stone analysis following stone passage or removal to determine stone type is important to help prevent future recurrences.


Colicky pain results when a kidney stone lodges in the ureter (tube connecting the kidney to bladder) during the process of passage. Because of excruciating pain and the inability to find a comfortable position, stones frequently result in an emergency room visit. Other symptoms are sweating, nausea and vomiting, blood in the urine and urinary urgency and frequency as the stone passes into the terminal part of the ureter that is tunneled within the bladder wall. In the emergency department patients are usually hydrated intravenously, given pain medications and undergo imaging. Most kidney stones can be managed on outpatient basis with analgesics, a medication to facilitate stone passage, and a strainer to capture the stone.

Size Matters

Stones vary in size tremendously, ranging from tiny stones the size of sand particles to huge stones that fill the entirety of the inner aspect of the kidney, appropriately labeled “staghorn” stones because of their shape. Whether a stone will pass spontaneously is dependent upon factors including stone size, shape, location and ureteral anatomy.  The smaller the stone and the closer to the bladder, the greater the likelihood for spontaneous passage. Most stones 5 mm and smaller will pass spontaneously, stones 5-8 mm may pass, and those 8 mm or larger are unlikely to pass.  The smoother and less irregular they are, the more easily they will pass. Passage is also influenced by the internal diameter of the ureter and the nuances of ureteral anatomy. Once a stone passes into the urinary bladder, passage out the urethra (tube from the bladder out) is usually rapid and painless.

To Intervene or Not?

A stone will require intervention if it causes continued symptoms and does not pass in a reasonable amount of time.  Aside from unremitting pain, other reasons for intervention are unrelenting nausea and vomiting with dehydration, larger stones that are not likely to pass, significant obstruction of the kidney, a high fever from a kidney infection that does not respond to antibiotics, a solitary kidney and certain occupations that cannot risk impaired functions such as airline pilots.

What’s New in the Stone World?

  • The recognition that lifestyle factors are major risks
  • New and improved imaging techniques
  • Medical “expulsive” therapy to help stone passage
  • Technological refinements in surgical management

It is now well understood that although there are many causes of kidney stones, lifestyle factors are of paramount importance. Body weight, dietary habits and the quantity of fluids consumed are all important considerations. The prevalence of stone disease has increased substantially, paralleling the epidemic of obesity and type II diabetes. Additionally, effective treatment is more challenging in this population. Obesity has metabolic consequences including increased urinary excretion of calcium, oxalate and uric acid (all common stone constituents); furthermore, the obese population tends to consume excessive protein and salt, further increasing stone risk.  

The diagnostic tools used to evaluate kidney stones have advanced considerably. Years ago, the imaging study of choice was intravenous urography (a series of x-rays taken after injecting contrast in a vein). This has been replaced with unenhanced computerized tomography (CT) urography, a sophisticated means of visualizing the anatomy of the urinary tract that does not need to use intravenous contrast (thus avoiding the potential risks of contrast). Diagnostic imaging has evolved further with current techniques using substantially reduced radiation exposure. CT urography precisely pinpoints the size and location of the stone and the extent of the obstruction. It provides insight into the mineral composition of the stone and also images other organs in the abdomen and pelvis aside from the urinary tract.  Ultrasonography affords the advantage of less expense and no radiation, but is not on a par with CT imaging in terms of diagnostic capability.

Medical expulsive therapy is now routinely used to facilitate passage of stones. Medications including Flomax, Uroxatral and Rapaflo, traditionally used to improve urinary symptoms due to benign prostate enlargement, are prescribed “off label” to help relax the smooth muscle of the ureter and aide stone passage. When one is seen in the emergency room with a stone that is deemed manageable on an outpatient basis, they are routinely sent home with pain medication, one of the expulsive medications and a strainer to capture the stone when it passes.

Minimally invasive, outpatient techniques to manage kidney stones are now standard.  Extracorporeal shock wave lithotripsy (ESWL) uses new generation machines that focus external shockwaves on the stone to break it into tiny pieces that can be more readily passed. Imaging of the stone during the procedure can be done with traditional fluoroscopy (imaging that uses a continuous x-ray image on a monitor), or alternatively, using ultrasound imaging that uses no radiation. Our urology group, New Jersey Urology, uses the advanced technology of The Stone Center of New Jersey for our patients who need ESWL.

Ureteroscopy with laser lithotripsy is a procedure in which a narrow lighted instrument is passed up the ureter to directly visualize the stone and a laser fiber is used to pulverize the stone. This procedure has benefited from increasingly miniaturized telescopes with increased flexibility, improved fiber-optics, and advances in laser technology.  A ureteral stent is typically placed on a temporary basis after removal of the stone fragments to allow the ureter to heal and prevent obstruction.

If a stone is too large for the aforementioned procedures, alternatives include percutaneous lithotripsy (removal of kidney stones via a special scope that is passed through the tissues of the flank directly into the kidney) and robotic-assisted laparoscopic procedures.

Encore Performances

Although the majority of people with a kidney stone will have only one isolated episode, about 35% will experience recurrent episodes. Recurrent stone formers benefit from a metabolic evaluation and an analysis of urine collected for 24 hours to implement prevention strategies.

Strategies to Reduce Risk for Becoming a Kidney Stoner

  • Healthy lifestyle (healthy diet and body weight, exercise, etc.)
  • Hydration (make sure your urine looks more clear than amber)
  • Consume citrate (high levels are present in citrus, particularly lemons), an inhibitor of stone formation
  • Avoid excess Vitamin C
  • Avoid high protein diets
  • Avoid excessive salt (kidneys tend to reabsorb sodium and compensate by excreting calcium in the urine)

Wishing you the best of health,

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Dr. Andrew Siegel is a physician and urological surgeon who is board-certified in urology as well as in female pelvic medicine and reconstructive surgery.  He is an Assistant Clinical Professor of Surgery at the Rutgers-New Jersey Medical School and is a Castle Connolly Top Doctor New York Metro AreaInside Jersey Top Doctor and Inside Jersey Top Doctor for Women’s Health. His mission is to “bridge the gap” between the public and the medical community. He is a urologist at New Jersey Urology, the largest urology practice in the United States.  He is the co-founder of PelvicRx and Private Gym.  His latest book is Prostate Cancer 20/20: A Practical Guide to Understanding Management Options for Patients and Their Families. 

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Video trailer for Prostate Cancer 20/20

Preview of Prostate Cancer 20/20

Andrew Siegel MD Amazon author page

PROSTATE CANCER 20/20 is now available at Audible, iTunes and Amazon as an audiobook read by the author (just over 6 hours). 

Dr. Siegel’s other books:

FINDING YOUR OWN FOUNTAIN OF YOUTH: The Essential Guide to Maximizing Health, Wellness, Fitness and Longevity

PROMISCUOUS EATING— Understanding and Ending Our Self-Destructive Relationship with Food

MALE PELVIC FITNESS: Optimizing Sexual and Urinary Health

THE KEGEL FIX: Recharging Female Pelvic, Sexual, and Urinary Health


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3 Responses to “Kidney Stone Update 2021”

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