Definition

Kidney stones are pieces of a stone or crystal-like material. These stones form inside the kidneys or urinary tract. The kidneys remove waste (in the form of urine) from the body. They also balance the water and electrolyte content in the blood by filtering salt and water.

There are several types of kidney stones:

  • Most common type has mostly calcium along with phosphate or oxalate.
  • Others types contain uric acid, struvite, and/or cystine.

Kidney Stone

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Causes

Approximately 50% of kidney stones are due to unknown causes. Some of the known causes include:

  • Chemotherapy (ie, uric acid stone)
  • Too much oxalate in urine (hyperoxaluria)
  • Too little magnesium in urine (hypomagnesemia)
  • Too much calcium in the urine (hypercalciuria)
  • Too much calcium in the blood (hypercalcemia)
  • Too little citrate in the urine (hypocitraturia)
  • Tiny bacteria around which a stone can form
  • Too much uric acid in the urine (hyperuricuria, gout )
  • Bacteria that produce enzymes that increase the amount of ammonia and struvite in the urine
  • Inherited abnormality in the way the body handles cystine
  • Certain medications (such as indinavir )
  • Retention of urine

Risk Factors

These factors increase your chance of developing kidney stones. Tell your doctor if you have any of these risk factors:

Symptoms

Occasionally, kidney stones do not cause symptoms, and they leave the body in the urine. The condition, though, can cause severe pain.

Symptoms include:

  • Sharp, stabbing pain in the lower back that may occur every few minutes lasting from 20 minutes to one hour
  • Pain in the lower abdomen and groin area, labia, or testicles
  • Nausea, vomiting, or diarrhea
  • Blood in the urine
  • Frequent urge to urinate
  • Burning pain during urination
  • Fever
  • Urinary tract infection

Diagnosis

The doctor will ask about your symptoms and medical history, and perform a physical exam.

Tests may include:

  • Urinalysis—to look for blood, pus, bacteria, and crystals in the urine
  • Blood tests—to check kidney function, calcium , and uric acid levels
  • Urine culture —if infection suspected
  • Spiral CT scan—a type of x-ray that uses a computer to make pictures of the inside of the kidney
  • Ultrasound —a test that uses sound waves to examine the kidneys
  • Intravenous pyelogram (IVP) — special x-ray that produces images of the urinary system (less commonly used today)
  • 24-hour urine—to check levels of many factors, including calcium , phosphorus , uric acid, oxalate, and citrate

Treatment

Treatment depends on the size and location of the kidney stone. Treatment may include:

Water

For small kidney stones, drinking at least two or three quarts of water a day helps the body pass the stone in the urine. The doctor may provide a special cup to catch the stone when it passes so that it can be analyzed. If you are having a hard time keeping fluids down, you may need to be hospitalized to receive fluids in your vein.

Medications and Nerve Stimulation

Your doctor may recommend that you take pain medication. You may need medication that is given in the vein or in the muscles. Nerve stimulation therapy might also be helpful in relieving pain. * 2

Medications used to treat high blood pressure (eg, calcium channel blockers and alpha blockers) may help your body pass kidney stones. * 1

Surgery

Surgery may be necessary if the stone is:

  • Very large or growing larger
  • Causing bleeding or damage to the kidney
  • Causing infection
  • Blocking the flow of urine

Types of surgery include:

  • Stent placement—used to allow urine to pass
  • Ureteroscopy and stone basketing or laser lithotripsy—a camera is used to locate the stone, and a tiny basket is used to remove the stone
  • Extracorporeal shock wave lithotripsy (ESWL) — uses shock waves to break up stones that are too large to pass
  • Percutaneous nephrolithotomy—uses a scope placed through a small tube in the back to remove a large stone
  • Lithotomy—open surgery to remove a stone (rarely used now)

If you are diagnosed as having kidney stones, follow your doctor's instructions .

Prevention

Once you have formed a kidney stone, you are more likely to form another. Here are some steps to prevent this condition:

  • Drink plenty of fluids, especially water.
  • Talk to your doctor about what diet is right for you. Depending on the type of stone you have, you may be advised to:
    • Avoid apple and grapefruit juices.
    • Drink more cranberry juice.
    • Avoid foods high in oxalate, such as spinach.
    • Eat less meat, fish, and poultry. These foods increase urine acidity.
    • Decrease your sodium intake (especially if you have calcium stones).
    • Increase your intake of magnesium .
    • Drink lemonade daily.
    • Increase your fiber intake.
    • Lose weight .
  • If you have an enlarged parathyroid gland, you may need to have it removed surgically.
  • Medications may include:
    • Drugs that control the amount of acid in the urine
    • Allopurinol or sodium cellulose phosphate—to treat urine high in calcium
    • Hydrochlorothiazide (a diuretic)—to treat urine high in calcium
    • Thiola—to reduce the amount of cystine in the urine