• Caucasians more than Afro-Americans
• Men more often than Women
• Persons 20 to 40 years of age
• People with a family history of kidney stones
• Those having frequent attacks of kidney stones

Normal Kidney Function

Our kidneys make urine by filtering blood through specialized structures called glomeruli, removing waste products produced by the body's cells. The normal components of urine include water, urea, and small amounts of minerals including sodium chloride, potassium chloride, phosphates, calcium, organic salts and bile pigments.

How Stones Form

These components of urine normally remain dissolved. However, when there is not enough water to keep them dissolved or when too much of one of these minerals is present, it can crystallize to form stones. Thus, not drinking enough water is the most important cause of kidney stones. Younger people often underestimate the amount of liquids they drink while physiologic changes associated with aging make older people less sensitive to thirst. With relative dehydration tiny crystals form in the urine and may be deposited on the inner surface of one or both of the kidneys. Stones are formed as crystals combine together.

70% to 80% of all kidney stones are composed of calcium oxalate. Decreasing calcium intake is no longer recommended by doctors because we now know that oxalate is the main culprit.

Current recommendations for those susceptible to kidney stones are to maintain normal calcium intake but to cut down on oxalate rich foods and avoid excess vitamin C (excess vitamin C is converted to oxalate).

Other causes of kidney stones

In addition to lack of water combined with an oxalate rich diet include:

• Excess vitamin D (more than 1 gram per day) and/or Vitamin C (more than 200 milligrams per day)
• Prolonged immobilization (bed rest) causes the release of calcium from bones
• Hyperparathyroidism- increases the amount of calcium in the blood

Less common types of stones include:

• Uric-acid stones- seen in persons with gout
• Struvite (triple phosphate) stones- seen in persons with chronic urinary tract infections. These stones may be quite large
• Cystine stones- seen in children with a disorder of metabolism

Symptoms of Kidney Stones

Stones may vary in size from microscopic to over an inch in size. They may stay in the kidney or may travel down the ureter (urine duct connecting the kidney to the bladder). Extremely small stones may pass without a person even knowing it. Larger stones may get stuck in the ureter and block it. Urine, unable to flow freely, may cause the part of the ureter behind the blockage to dilate. If the blockage lasts long enough (typically more than several weeks) injury to the kidney may occur.

However, by kidney stone standards even a stone as small as 2-3 millimeters (1/12 th to 1/8 th inch) can cause excruciating pain as it passes down the ureter towards the bladder. Stones less than 5 millimeters in size almost always pass on their own while stones larger than 6 millimeters do not pass on their own most of the time.

The pain from passing a kidney stone is typically sharp and cramping. It may begin in the back and side where the kidneys are located. As the stone moves down the ureter the location of the pain may sometimes change. It is fairly common for persons to feel pain in the groin and testes (men). Nausea, vomiting, and sweating chills are also common.

Diagnosing a Kidney Stone

The diagnosis of a kidney stone is usually obvious by the symptoms present. In 85% of cases a small amount of blood is present in the urine. This blood, caused by the stone scraping against the lining of the ureter, may not be visible except under microscopic view.

Your doctor will take a history and analyze your urine. A CT scan (computerized tomography) may be ordered if your pain persists despite medical treatment. Newer generation CT scan is the quickest and most sensitive way of detecting kidney stones. A CT scan can tell both the location and size of a stone. It has largely replaced intravenous dye and regular x-rays for detecting kidney stones. Ultrasound may be used but is more likely to miss small stones and is more susceptible to differences in patient size and interference from gas in the intestines.

Treating an Attack

Most stone pass within 3 days. Mild attacks may be treated at home by drinking more water and using NSAIDS (nonsteroidal anti-inflammatory drugs such as Ibuprofen or naprosyn) or oral narcotic containing medications prescribed by your doctor.

More severe pain, especially when accompanied by nausea and/or vomiting, will require a visit to your doctor or emergency room. You may receive intravenous or intramuscularly injected pain medications. These medications may include NSAIDS (Torodal™) or narcotic medications with or without an additional medicine for nausea and/or vomiting. All of these medications are effective in greatly decreasing or totally relieving the pain of a kidney stone.

Additionally, your doctor may infuse intravenous fluids through a catheter placed in your vein. This helps correct dehydration, increase urine output and flush the kidney stone into your bladder. Once in the bladder a kidney stone usually passes with ease and little additional pain.

If your pain is resolved or if your pain is bearable and CT scan shows a stone 6 millimeters or less your doctor will send you home with a prescription for pain medication, instructions to drink at least 8 8ounce glasses of water a day, and a urine strainer. You will be instructed to strain your urine for the next 3 days for any stone or grain size particles. Save these and take them to your doctor for analysis.

Referral to a Urologist is indicated for:

• Stones that don't pass
• Continuing symptoms (i.e. pain)
• Stones diagnosed as 6 millimeters or larger.

Treatment for Stones that don't pass

About 10% of stones don't pass on their own and need to be removed. Methods include:

• Lithotripsy is the least invasive and most commonly used. After the stone is located ultrasonic sound waves are used to shatter the stone into fragments small enough to pass. An anesthetic or pain killer is usually need as this procedure is causes moderate pain in many patients.
• Ureteral Stenting uses a small metal tube inserted through the bladder into the ureter to keep the ureter open so a stone may pass through it.
• Ureteroscopy. Your doctor inserts a small scope through the urethra into the bladder and looks into the ureter. Once the stone is seen it is either grabbed with a small cage like device or shattered with a laser. This procedure will also require anesthesia or pain medication.
• Percutaneous nephrolithotomy is the microscopic surgical removal of a kidney stone from the kidney. This procedure may be required to remove a large stone from the kidney or any place that lithotripsy won't work.

AVOIDING KIDNEY STONES

• Drink plenty of fluids (at least eight 8 ounce glasses of water a day) unless your doctor has you on fluid restriction for other problems.
• Persons at risk should decrease consumption of oxalate-rich foods such as nuts, beets, cola drinks, excess vitamin C containing foods and beverages, leafy greens and chocolate.
• If you have frequent attacks your doctor may prescribe diuretics (water pills) that will reduce the calcium in the urine.
• If you have uric acid kidney stones your doctor may prescribe a medication called allopurinol to decrease uric acid levels.

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