Posts Tagged ‘shock wave lithotripsy’

Are You A Kidney Stoner? Update On Technological Advances

January 30, 2016

Andrew Siegel MD 1/30/16

Continuing on the theme of technological advances in medicine, today’s entry is on innovations in the diagnosis and management of kidney stones. Kidney stones cause excruciating pain, on par with the most painful human experiences– childbirth, broken bones, gout and impaired blood flow to organs.  Kidney stones are a common affliction with about 10% of Americans having experienced their misery. The good news is that most 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 virtually gone by the wayside.

What’s new in the world of kidney stones?

  1. Our recognition that lifestyle factors are major risks
  2. New and improved imaging techniques
  3. Technological refinements in surgical management
  4. Medical “expulsive” therapy to help stone passage

It is now well understood that although there are many causes of kidney stones, lifestyle factors are of paramount importance. This includes body weight, dietary habits and the quantity of fluids consumed. The prevalence of stone disease has DOUBLED in the last 15 years, paralleling the epidemic of obesity and type II diabetes. The more obese you are, the more likely it is that you will experience a kidney stone and the more difficult it will be to effectively treat it. Why is this so?  Obesity has metabolic consequences including increased urinary excretion of calcium, oxalate and uric acid (all common stone constituents); additionally, the obese population tends to consume excessive protein and salt, further increasing stone formation risk.  Another key risk factor is not consuming sufficient volumes of fluid to maintain a well hydrated state.

The diagnostic tools used to evaluate kidney stones have advanced considerably. Years ago, the imaging choice was intravenous urography (a series of x-rays taken after injecting contrast in a vein), which has been supplanted by unenhanced abdominal computerized tomography (CT) urography, a more sophisticated means of visualizing the anatomy of the urinary tract that does not use contrast (thus avoiding the potential risks of contrast) and has recently evolved further in terms of reduced radiation exposure. It 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 the other organs in the abdomen and pelvis aside from the urinary tract.


CT image of patient with stones circled in red in the lower poles of both kidneys, yellow arrow points to right kidney, blue arrow to left kidney.

In terms of stone evaluation, ultrasonography affords the advantage of less expense and no radiation, but is not on a par with CT imaging in terms of diagnostic capability.

sono kidney stone

Ultrasound image of kidney with stone circled in red; blue arrows point to border of kidney.

Minimally invasive techniques to manage kidney stones are now the norm.  Shock wave lithotripsy uses fourth generation machines that generate and focus external shockwaves at the stone.  This procedure is done under sedation, using fluoroscopy (real-time x-ray imaging) to image the stone, resulting in fragmentation of the stone into pieces that can be passed. Ureteroscopy and laser lithotripsy, done under general anesthesia, is a procedure in which a narrow lighted instrument is passed up the ureter (tube connecting the kidney to bladder) to directly visualize the stone and a laser fiber is used to pulverize the stone into pieces.  This procedure has benefited from miniaturized telescopes with increased flexibility, improved optic lens systems and fiber-optic light sources as well as advances in laser technology.

Medical expulsive therapy is now routinely used to help facilitate the passage of the stone or stone fragments. Alpha-blocker medications including Flomax, Uroxatral and Rapaflo, traditionally used to improve urinary symptoms due to prostate enlargement, are utilized “off label” to help relax the smooth muscle of the ureter and aide stone passage.

Groans, moans and other symptoms

Colicky pain results when a stone gets lodged in the ureter during the process of passage. Because of excruciating pain and the inability to find a comfortable position, stones frequently result in a visit to the emergency room. Other typical symptoms are sweating, nausea and vomiting, blood in the urine and urinary urgency and frequency. In the emergency department patients are usually hydrated intravenously, given pain medications and undergo CT imaging. Most kidney stones can be managed on outpatient basis with patients sent home on pain medication, an alpha-blocker medication and a strainer to capture the stone.

Will my stone pass?

Whether a stone will or will not pass is dependent upon factors including stone size, shape, and ureteral anatomy. 70% of stones less than 5 mm and 50% of those between 5–10 mm will pass, given sufficient time. 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.

Why do stones form?

Kidney stones form when minerals normally dissolved in the urine crystallize into solid particles. It starts out as a tiny “grain” that grows because the stone is bathed in mineral-rich urine that laminates mineral deposits around the grain. This crystal formation often occurs during periods of dehydration, typically prompted by summer heat, exercise, saunas, hot yoga, diarrhea, vomiting, being on bowel prep for colonoscopy, etc. Another big 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 increase the risk for stones.  Urinary infections with certain bacteria can promote stone formation. Parathyroid gland issues and high serum calcium levels increase one’s risk. Some stones have a genetic basis.

When to intervene?

If a stone does not pass in a reasonable amount of time and causes continued symptoms, it will require active intervention. 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 about recurrent stones?

Although the majority of people with a kidney stone will have only one isolated episode, about 35% will experience recurrent episodes. Because of the possibility of recurrence, it is important to identify the underlying metabolic causes in order to implement prevention strategies. For this reason it is important to analyze the mineral content of the stone and certainly for recurrent stones, to collect urine for 24 hours to do a metabolic evaluation.

Strategies to reduce your risk for stones

  • Healthy lifestyle (healthy diet and body weight, exercise, etc.)
  • Stay well hydrated (make sure your urine looks more clear than amber)
  • Consume citrate (high levels in citrus, particularly lemons), which is 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,

2014-04-23 20:16:29

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Kidney Stones…Ouch!

October 19, 2012

Andrew Siegel, M.D.   Blog # 80


I have chosen kidney stones as a topic since they are a very prevalent problem that I treat on an everyday basis, and a condition often related to our dietary habits, the quantity of fluids that we drink, and our weight status.

If you have ever suffered with a kidney stone, you truly know what excruciating pain is.  Many women who have experienced both passage of a kidney stone and natural childbirth without any anesthesia will report that the childbirth was the less painful of the two!

Stones are a common condition that has occurred in humans since ancient times; kidney stones have even been found in an Egyptian mummy dated 7000 years old.   The good news about stones is that most of them 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 virtually gone by the wayside.

Kidney stones form when minerals that are normally dissolved in the urine precipitate out of their dissolved state to form solid crystals. This crystal formation often occurs after meals or during periods of dehydration. The lion’s share of kidney stones manifest themselves during sleep, at a time of maximal dehydration.  Dehydration is also why kidney stones occur much more commonly during hot summer days than during the winter. This past summer—one of the hottest on record—kept urologists very busy in terms of caring for patients with kidney stones.   Anything that promotes dehydration can help bring upon a stone—including exercise, saunas, hot yoga, diarrhea, vomiting, being on bowel prep for colonoscopy, etc.

In addition to dehydration, another factor that can contribute to kidney stone formation is excessive intake of certain vitamins. The biggest culprit is Vitamin C, also known as ascorbic acid.   When metabolized by the body, Vitamin C is converted into oxalate, one of the components of calcium oxalate stones, the most common variety of stone.  The problem is that vitamin C is a water-soluble vitamin, so any excessive intake is not stored in the body but appears in the urine in the form of oxalate. Additionally, excessive dietary protein intake, fat intake, and sodium are all associated with an increased risk for kidney stones. Having inflammatory bowel disease or previous intestinal surgery can also increase the risk for stones.     Urinary infections with certain bacteria can promote stone formation. Having a parathyroid issue and high circulating calcium levels is another cause of kidney stones.  Obesity is also a risk factor for kidney stones. Some stones have a genetic basis, with a tendency to affect many family members.  My uncle is currently plagued with a stone lodged in his ureter and is scheduled for stone surgery on Monday, and both my father and brother have passed stones.  What does that bode for me?  So far I have been lucky.

A kidney stone starts out as a tiny sand particle that grows as the “grain” is bathed in urine that contains minerals.   These minerals are deposited and coalesce around the grain.  They can grow to a very variable extent so that when they start causing symptoms they may range from being only a few millimeters in diameter to filling the entire kidney.

Some stones are “silent” because they cause no symptoms and are discovered when imaging studies are done for other reasons.  However, most stones cause severe pain known as colic. Colicky pain is often intermittent, originating in the flank area and radiating down towards the groin.  It often causes an inability to get comfortable in any position, and is associated with sweating, nausea, and vomiting. Kidney stones can also cause blood in the urine, sometimes visible and, at other times, only on a microscopic basis. When a stone moves into the ureter (the tube running from the kidney to the bladder), it can become impacted and block the flow of urine. Stones can sometimes cause lower urinary tract symptoms such as urgency and frequency, particularly when the stone approaches the very terminal part of the ureter that is actually tunneled through the wall of the bladder.

Kidney stones are usually any easy diagnosis to make, based upon their rather classical presentation, although on occasion, a stone causes no symptoms whatsoever and is picked up incidentally on an imaging study such as an ultrasound, a CAT scan, or an MRI.   The imaging study of choice for evaluating a kidney stone is an unenhanced CAT scan (without contrast).   A plain x-ray of the abdomen is very useful for stones that contain calcium, and thus are readily visible on an x-ray.

Most stones will pass spontaneously without intervention given enough time.   Conservative management involves hydration, analgesics and the use of a class of medications known as alpha-blockers that can help facilitate stone passage by relaxing the ureteral smooth muscle.   As long as the pain is manageable and there is progressive movement of the stone seen on imaging studies, conservative management can continue to be an option.  Intervention is mandated under the following circumstances: intolerable pain; refractory nausea and vomiting with dehydration; larger stones that are not likely to pass; failure of a stone to pass after a reasonable amount of time; 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 an airline pilot.

There are a number of minimally invasive means of treating kidney stones depending upon the size of the stone, its location, and the degree of obstruction of the urinary tract.  Gone are the days when treating a kidney stone required a painful incision and a prolonged stay in the hospital.  Most kidney stones now are managed on an ambulatory basis. Shockwave lithotripsy is commonly used to treat stones in the kidney or upper ureter.  Typically done under intravenous sedation, shockwave lithotripsy uses shockwaves directed at the kidney stone via x-ray guidance to fragment the stones into pieces that are small enough so that they then can then pass down the ureter, into the bladder and out the urethra with the act of urinating.  Another means of managing stones, particularly amenable to stones in the lower ureter but also applicable to any stone, is ureteroscopy and laser lithotripsy.  This procedure is done under general anesthesia. A narrow lighted instrument known as a ureteroscope is passed up the ureter to visualize the stone under direct vision.  A laser fiber is then utilized to break the stone into tiny particles.  The largest fragments are removed using a special basket. A ureteral stent is often left in place after this procedure to allow the ureter to heal as well as to prevent obstruction of the kidney.

You are at high risk for kidney stones if you:

  • Don’t drink enough fluids
  • Have an occupation that requires working in hot environments, such as a chef
  • Exercise strenuously without maintaining adequate hydration
  • Are a male, since the male to female ratio of kidney stone incidence is 3:1
  • Had a previous kidney stone, since about 50% of people who have a stone will experience a recurrence
  • Have a family history of kidney stones
  • Have a urinary tract obstruction
  • Have an excessive intake of oxalate, calcium, salt, protein and fat
  • Take excessive amounts of vitamin C, A, and D
  • Have an intestinal malabsorption
  • Have gout
  • Have parathyroid disease

The key to preventing kidney stones is to stay well hydrated, particularly when exposed to hot environments or when exercising for prolonged periods of time. It is also important to avoid overdoing it with certain vitamins—particularly vitamin C—a major risk factor for kidney stones.  The two biggest risk factors for kidney stones are, in fact, dehydration and excessive intake of vitamin C. Chances are that if you have a healthy diet, you have more than adequate intake of vitamin C and any extra is potentially dangerous. A good sign of adequate hydration is the color of your urine: the urine of a well-hydrated person will look light in color like lemonade, whereas the urine of a dehydrated person will look like apple juice.

So drink up, particularly on hot days…and eat an orange instead of popping a vitamin C supplement…your kidneys will thank you!

Andrew Siegel, M.D.

Author of Promiscuous Eating: Understanding and Ending Our Self-Destructive Relationship with Food:

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For a nice booklet on kidney stones in PDF, go to and click on patient education and then on ABCs of Kidney Stones