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 Is New In The World Of Kidney Stones?
- Our recognition that lifestyle factors are major risks.
- New and improved imaging techniques.
- Technological refinements in surgical management.
- 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 quantity of fluids consumed.
How Is Obesity Linked To Kidney Stone Risk?
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).
- 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.
Techniques Used To Evaluate Kidney Stones
1. CT Urography
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, also known as CT urography.
It is 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.
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.
2. Minimally Invasive Techniques
These techniques are now the norm to manage kidney stones.
Shock Wave Lithotripsy
This technique uses fourth generation machines that generate and focus external shock-waves 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
These techniques, 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.
3. Medical Expulsive Therapy (MET)
MET 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 aid stone passage.
Kidney Stones: 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. Reasons for intervention are:
- Unremitting pain.
- 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).
