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Types of Kidney Stones

X-rays of Egyptian mummies dating back 8000 to 10,000 years ago show evidence of stones. Since World War II, the incidence of stone disease has been increasing dramatically in the Western industrialized nations. The stone "boom" is tied to our diets. Today, approximately 1 in 15 people in the industrialized world will develop
kidney stones. The incidence rate increases to 20–25% in the Middle East, because of increased risk of dehydration in hot climates. Kidney stones happen to approximately 1 in 10 Americans over the course of a lifetime and they occur most commonly in men between the ages of 30 to 50, but those as young as 20 can develop stones too.

What're Kidney Stones and Why They're Serious

Kidney stones
are formed in the urinary tract and are mainly composed of body's waste products. Your kidneys normally eliminate these wastes in urine. When there is too much waste, or not enough fluid to flush it out, it comes together to form a "stone." They can be as small as a grain of salt or as large as a golf ball. When the kidney eliminates these stones, the pain can be excruciating. It is often compared to childbirth or surgery without anesthesia. It's hard to believe that something so little can cause so much pain.

The symptoms of stones include sudden pain in the side, groin, genital, or abdomen. It can cause nausea; vomiting; frequent, painful urination; constipation; or diarrhea. Loss of appetite and sweating can also occur. Finally, hematuria (bloody urine) is commonly present due to damage to the lining of the urinary tract.

People who have made a kidney stone are likely to make another. A minor stone problem can easily become a major one. After numerous episodes of
renal colic (kidney stones), especially if it becomes complicated by infection, you can do permanent damage to one of both of your kidneys. Note that women are more prone to urinary tract infections.

Varieties of Kidney Stones

Kidney stones
come in many different sizes, shapes, and, most importantly, compositions. Each stone type has its own causes, complicating factors, and dietary emphasis. Often a stone will contain a combination of these types:

Calcium-containing stones
  • 75% kidney stones contain calcium oxalate.
  • When excess amounts of calcium and oxalate accumulates in the urine, they can form calcium oxalate crystals, which can grow into kidney stones.

Uric acid stones
  • 10% kidney stones contain uric acid stones.
  • Uric acid results from the metabolism of the purines, which are found in all animal protein and many seeds and plants.

  • Three factors favor uric acid stones:
    • The presence of a large amount of urate in the urine.
    • A low urine volume, which makes the urine concentrated.
    • A continually acid urine. In a normal, healthy person, the urinary pH will rise to over 7.0 after a meal (this rise is referred to as the "postprandial alkaline tide"). Uric acid stone formers lose this rise, and their urinary pH remains at or close to 5.0 all the time.
    • It's interesting to note that the patient who begins making stones at age 50 is likely to have uric acid not calcium stones. Uric acid stones are the one kind of stone whose incidence increases with age.
  • Uric acid can exists in two forms:
    • Uric acid
    • Urate
      • The urate is much more soluble. As the pH of the urine rises from 5.0 to 7.0, more of the uric acid is converted into urate. Its solubility is 11 times higher at pH 7.0 than it is at pH 5.0.
      • The urate form of uric acid can promote the formation of calcium oxalate stones.
Struvite, or infected, stones
  • 10% kidney stones contain struvite stones.
  • Struvite, or infected, stones are among the most difficult and dangerous problems in stone disease because of the potential of life-threatening complications from infection.
  • These stones are found mainly in women with recurring urinary infections, paralyzed patients, and patients with abnormal urinary tracts.
  • Struvite stones are often called triple phosphate stones because they contain 3 different elements: magnesium, ammonium, and calcium.

Cystine stones
  • Result from an uncommon hereditary metabolic disorder and account for fewer than 1% of stone cases.
  • Cystinuria is an uncommon genetic disorder that causes the kidney to excrete too much of the amino acid cystine in the urine. If there is too much cystine in the urine, it can form stones.

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Photo Credit
  1. 月 攝影
  1. "No More Kidney Stones" by John S. Rodman, M.D., R. Ernest Sosa, M.D., and Cynthia Seidman, M.S., R.D, with Rory Jones.
  2. Kidney Stones (Wikipedia)
  3. Risk Factors of Kidney Stones
  4. Risk Factors of Kidney Disease
  5. 9 Unknown Signs You’ll Get Kidney Stones and How to Prevent Them
  6. Calcium plus vitamin D supplementation and the risk of fractures
    • Calcium with vitamin D supplementation increased the risk of kidney stones
  7. Clinician’s Guide to Prevention and Treatment of Osteoporosis
    • the risk of kidney stones increases when calcium intake exceeds 1,200–1,500 mg per day