Kidney Stones

Pronounced: REE-nul KALK-you-lie

(Renal Calculi)

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Definition | Causes | Risk Factors | Symptoms | Diagnosis | Treatment | Prevention | Organizations

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Definition

Kidney stones are pieces of stone-like material that form on the walls of the kidney. The kidneys are two bean-shaped organs in the lower back. Their main function is to remove waste from the body and to balance the water and mineral content of the blood by removing water. The waste and water combine to form urine.

There are several types of kidney stones. The most common type contains mostly calcium along with phosphate or oxalate. Others contain uric acid, struvite, and/or cystine.

Causes

Although sometimes the cause of kidney stones is not known, they may be caused by:

• Too much calcium in the urine (hypercalciuria)
• Too much oxalate in the urine (hyperoxaluria)
• Too much calcium in the blood (hypercalcemia)
• Too little citrate in the urine (hypocitraturia)
• Tiny bacteria around which a stone can form
• To much uric acid in the urine (hyperuricuria)
• Bacteria that produce enzymes that increase the amount of ammonia and therefore struvite in the urine (This allows struvite stones to form)
• Inherited abnormality in the way the body handles cystine
• Allopurinol treatment (for gout)

Risk Factors

A risk factor is something that increases your chance of getting a disease or condition.

• Race: white
• Sex: male
• Age: 20-40 years old
• Geographical location (residents of the Southeast United States have a greatly increased risk)
• Family members who have had kidney stones or gout
• Previous kidney stones
• Taking calcium supplements or vitamin D in excessive doses
• Pregnancy
• Low birth weight babies receiving intravenous feedings
• Being overweight
• Fasting
• Other medical conditions, including:
  • High blood pressure
  • Kidney disease
  • Overactive parathyroid
  • Chronic diarrhea
  • Ulcerative colitis
  • Crohn's disease
  • Leukemia
  • Lymphoma
  • Urinary tract infections
  • Sarcoidosis
• Immobility, paralysis, being bedridden
• Medications, including:
  • Several drugs used in the treatment of AIDS
  • Cancer chemotherapy agents
  • Diuretics
  • Thyroid medications
  • Antacids
• Previous intestinal bypass surgery

Symptoms

Occasionally kidney stones do not cause symptoms and they leave the body in the urine. Kidney stones often, however, cause severe pain.

Symptoms include:

• Sharp, stabbing pain in the lower back that may occur every few minutes
• Pain in the lower abdomen and groin area
• Nausea and vomiting
• Blood in the urine
• Frequent urge to urinate
• Burning pain during urination
• Fever and chills

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

X-ray – a test that uses radiation to take a picture of the kidney

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 scans the urinary system

MRI Scan – a test that uses magnetic waves to make pictures of the inside of the kidney

Treatment

Treatment depends on the size of the kidney stone.

Water and Pain Medication

For small kidney stones, drinking at least two or three quarts of water a day helps the body pass the stone in the urine. You can take pain medication as needed. The doctor may provide a special cup or strainer 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 intravenous fluids. In addition, you may need intravenous or intramuscular pain medication.

Surgery

Surgery for stone removal may be necessary if it is:

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

Types of surgery include:

Ureteroscopy and Stone Basketing - involves a scope slipped up the urethra, into the bladder, and into the ureter. A tiny basket is used to try to snare the stone.

Stent Placement - if the ureter is obstructed, a tiny tube may be placed in the ureter to allow urine to pass, and to try to avoid kidney damage.

Extracorporeal Shock Wave Lithotripsy (ESWL) - this procedure uses shock waves to break up stones that are too large to pass. It requires anesthesia and may cause blood in the urine and minor back pain for a few days.

Percutaneous Shock Wave Lithotripsy - uses a shock wave device, but requires a small incision in the flank.

Percutaneous Nephrolithotomy - uses a scope placed through an incision in the flank to remove a kidney stone that is too big to pass.

Lithotomy - open surgery to remove a kidney stone. This surgery is rarely used now.

Prevention

Once you have formed a kidney stone, you are more likely to form another. But you can prevent more stones from forming.

• Drink plenty of fluids, especially water.
• Don't change your diet without consulting your doctor. Recommendations will be based on the type of stones you've had, and the results of your 24-hour urine tests. Be sure to ask your doctor for a list of the foods you should avoid, or meet with a dietician who can help you understand your dietary restrictions.
• You may be advised to:
• Avoid apple and grapefruit juices.
• Increase intake of cranberry juice.
• Eat foods high in calcium, such as dairy products. Recent studies have shown that dairy products do not promote stone formation.
• Avoid calcium or vitamin D supplements or calcium-based antacids.
• Avoid foods that have added vitamin D.
• Avoid foods high in oxalate, such as spinach.
• If tests show your urine is unusually acidic, you may need to eat less meat, fish and poultry. These foods increase urine acidity.
• If you have calcium stones, you may be asked to decrease your sodium intake.
• If you have an enlarged parathyroid gland, you can have it removed surgically.
• Medications may include:
  • Drugs that control the amount of acid in the urine
  • Allopurinol or sodium cellulose phosphate for urine high in calcium
  • Hydrochlorothiazide (a diuretic)
  • Thiola to reduce the amount of cystine in the urine

Organizations

National Kidney Foundation
http://www.kidney.org/

American Foundation for Urologic Disease
http://www.afud.org/

SOURCE:

National Institute of Diabetes and Digestive and Kidney Diseases

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Last reviewed June 2001 by Medical Review Board