There are many potential causes of kidney stone formation. In general they are the result of a super concentration of chemicals in the urine that results in crystals being formed. One or more of the following may bring this on:

• A family genetic predisposition to form stones;
• An excess of calcium or certain other minerals in the diet (sometimes due to local geographic water or soil conditions);
• Intake of excess uric acid, certain medications, vitamin c, or vitamin D;
• A diet of fruits and vegetables high in oxalate (a by product of metabolism);
• Long term dehydration (possibly due to inadequate intake of fluids)
• And its resulting concentration of urine;
• Urinary infection;
• Living in an area where high temperatures cause sweating and loss of fluids; or
• Possibly, just leading a sedentary (low physical activity) lifestyle.

The function of the kidneys is to eliminate by products of metabolism. (The kidney's parts and workings are explained in detail and wonderfully illustrated at How the Kidney Works.) This means they are constantly collecting the major ingredients for kidney stones - including calcium, oxalate, and uric acid. Ideally these minerals are kept in suspension until they are passed out of the body. Too much metabolic by products insufficient fluid (urine) makes a person prone to kidney stone formation.

The over concentration of metabolic by products in the urine can cause these minerals to move out of suspension and crystallize. These small crystals that precipitate out of the super saturated urine will usually pass on out through the urinary tract, but they may begin to clump together. Any existing crystal makes it easier for other crystals to form. If they stay in the kidney very long, the crystals gradually grow larger and larger until they become a kidney stone so large that it cannot pass through the urinary tract.

Several underlying metabolic disorders may be the root cause of excessive calcium and oxalate forming stones in the kidney. The potential root causes include, but are not limited to the following:

1. A re-absorption of the calcium from the bones back into the blood system which the kidneys then filter out (resorptive hypercalciuria or hyperparathyroidism).

2. The intestines absorb too much calcium from the diet (absorptive hypercalciuria).

3. The kidneys filter out calcium from the blood but do not allow the reaborption of the calcium back into the blood as it should while it is still in the tubule of the kidney (renal hypercalciuria).

4. Several forms of bowel disease (ulcerative colitis, regional enteritis, etc.) which can contribute to high levels of urinary oxalate excretion.

5. Excess dietary intake of oxalate from foods such as green leafy vegatables. (See list of high oxalate foods later in this article.)

6. High levels of uric acid in the urine can act as a breeding ground for calcium oxalate stones.

7. Or, in a reverse manner, the lack of certain stone formation inhibitors normally found in the urine may not be present in sufficient quantities and thereby allow the formation of stones. One such ingredient is citrate; another is magnesium.

8. Infection stones are indicators of underlying infection in the urinary tract.

Kidney stones may be formed, grow in size, and stay immobile inside the kidney for years without any warning pain or other indicators. Most people don't know they are at risk for forming kidney stones until one or more have been formed. A few people have and pass small kidney stones without experiencing pain, but that is not the usual case. More often the kidney stone makes itself dramatically known when it begins to move through the urinary tract. A kidney stone attack has classic symptoms: an agonizing pain in the lower back just below the ribs spreading around to the front of the abdomen and often extending into the groin area. The pain may come in waves as the stone tries to move through the tube between the kidney and the bladder (the ureter). Sometimes there will be blood in the urine. Often there is nausea, vomiting, fever and chills. The abdomen or lower back may be painful to touch.

The severity of the pain is no indicator of the size of the passing kidney stone. This pain is often described as the worst pain a person has ever suffered .It is reported to be more painful than gun shots, surgery, broken bones, or even burns. The pain is not a result of the stone moving or tearing the ureter as a sufferer might suspect. Rather, the pain is due to the dilation or stretching of the urinary tract by the stone blocking the ureter.

More than one million people in the United States are hospitalized each year because of kidney stone attacks. A suffer should call their doctor or go to the hospital emergency room if they experience severe or persistent bleeding, if the pain continues to be severe, unrelenting and persistent, or if fever and chills or nausea and vomiting develop.

During a kidney stone attack the sufferer should drink large amounts of water (two to three quarts per day). Stay active. Do not go to bed (except for normal sleep periods). Physical activity may actually assist passage of the kidney stones.

Unless the kidney stone is larger than 1/4 inch (or 5mm) in diameter it will most likely pass without medical intervention ... except for the administration of pain killers to allow the sufferer to endure through the episode which may last for several days. Those stones between 1/4 inch and 1/2 inch in diameter are less likely to pass on their own.

If the kidney stone is larger than 1/2 inch (or 10mm) in diameter it will likely need to be either removed by surgery or by lithrotripsy. Stones have been known to become as large as the size of golf balls. It is not necessary to remove a stone unless it causes other problems. Large stones usually remain in the kidney without symptoms, although they may damage the kidney.

A complete diagnosis of kidney stones should include blood screens, 24 hour urine samples, provocative calcium loading tests, and stone analysis to determine the type of stone, its underlying cause, and proper treatment, and future stone prevention.

The kidney stone machine fragments kidney stones by use of extracorporeal shock wave lithrotripsy (ESWL). It uses high energy shock waves that are focused at the exact location of the stone (located by use of x-rays) while the anesthetized patient is located on a table covered with an enclosed water bag.

During a treatment up to 3000 lithrotripsy shock waves vibrate the stone so that it shatters into smaller sand-like fragments usually without injury to surrounding tissue. Pressure is felt, but not pain. This process is repeated until the doctors can see on the x-rays that the stone has been crushed by the shock waves. The resulting stone fragments (some not so small and most in jagged shapes) then pass out of the body over a period of time that may be as long as three months or more. Passing these fragments is similar to passing small stones. The most common type of stones, calcium oxalate, is the most difficult type to break up with shockwave lithrotripsy due to its extreme hardness. While some larger or complicated cases may require more than one treatment, lithotripsy usually allows the sufferer to return to their normal life (with the aid of medications to reduce the pain and nausea caused by passing the fragments) in just a few days.

Kidney stone removal surgery is necessary in less then 5% of stone cases. If the stones are in the kidney then the incision will be through the flank under the ribs. Hospitalization is 3-5 days and disability for 3-6 weeks. Ureteral surgery is less involved with a smaller incision through the skin in the front of the abdomen.

The usual procedure necessary to remove stones stuck in the ureter is ureteroscopy. This procedure is performed under regional anesthesia by passing a small instrument via the urethra and bladder and removing from the stone in the ureter. It is nearly 98% effective in removing the stone but that can leave the patient with residual ureteral cramping, bleeding, or pain for several days afterwards.

The chance of having recurrent stones is about 70-80 percent once a person suffers their first stone attack. Subsequently a person suffers a cumulative 10 percent chance per year of forming another stone. This translates into a 50% chance over a 5-year period of time. Family genetic tendencies can increase this risk.

The younger a person is when they have their first kidney stone attack the greater their personal risk of having additional attacks. Those between the ages of 35 and 50 are in their peak stone formation period.

Historically about 60 percent of individuals who have experienced one kidney stone will develop another within 7 years. But whereas just a few years ago recurrence of kidney stones was unavoidable, modern medical science has made recurrent kidney stones a preventable disease. With individualized medical therapy recurrence can be prevented in more than 95 percent of suffers.

Once the stone is retrieved identification of the chemical characteristics will allow medical treatment that can reduce your risk of developing additional stones. Therefore, it is important to catch the stone when it passes so that it can be chemically analyzed.

Most stones are made up of calcium or a combination of calcium and oxalate. These stones are seen quite well on x-rays. Calcium mineral combination stones cannot be dissolved with any known medicine. However kidney stones made up of uric acid are invisible to x-rays, but can sometimes be dissolved with the proper medications.

Common Chemical Make Up:

Calcium phosphate (8%)

Calcium oxalate (most common: 73%, most opaque)

Magnesium ammonium phosphate (also called "struvite" - often caused by an infection)

Uncommon Chemical Make Up:

Diammonium calcium phosphate

Magnesium phosphate

Rare Chemical Make Up:

Cystine (faintly opaque; 1%)

Urate (lucent - meaning translucent to x-rays; 7%)

Xanthine

One of the chief factors that puts people at higher risk for kidney stones is a high oxalate diet . Oxalate from foods is absorbed from the gut and excreted in urine. The oxalate forms a salt with calcium that has a low solubility factor (Precipitates into crystals easily). Even mild chronic dehydration can increase the likelihood of kidney stone formation. Inactivity has been associated with increased kidney stone formation: Russian astronauts in space for long periods have developed kidney stones.

Vitamin C and Vitamin D increase the formation of oxalates during the food digestion processes. (Not only do certain foods contain oxalate; additional oxalates can be formed as a by product of the natural metabolic process.)

The easiest step to take is to increase hydration. This applies to sufferers of all types of kidney stones. Drinking very large amounts of water - two or more quarts per day - is probably the most important step in reducing stone formation. It is recommended that sufferers increase their urine output to at least 2 quarts per 24-hour period. Drinking 2 to 3 quarts per day may reduce recurrence of stones by up to 90 percent.

A diet with high levels of sodium, sucrose, or animal protein increase the likelihood of kidney stone formation. Conversely, high levels of potassium, magnesium, and fluids lower the likelihood of kidney stone formation.

The Division of Urology at the Toa Payon Hospital in Singapore offers dietary advice for kidney stone patients including both what to eat as well as what not to eat. There are, also, medications available to reduce the tendency towards formation of certain types of stones.

One type of medication to reduce risk of formation of calcium oxalate stones introduces high levels of citrate into the kidneys. This citrate in the urine reduces the tendency for calcium oxalate stone formation. A similar increase in urinary citrate is generated by drinking lemonade (lemons are one of the good foods) containing at least 4 ounces of lemon juice per day.

It has been discovered that avoiding calcium may do more harm than good when it comes to kidney stone sufferers who have, in the past, been warned to avoid foods rich in calcium. According to a study of over 45,000 men conducted by the Harvard School of Public Health, men who get lots of calcium in their diets have a one-third lower risk of having kidney stones than do those who consume calcium sparingly. It seems that high dietary calcium actually blocks a chemical action which causes the formation of kidney stones by binding with oxalates (from foods) in the intestine which then prevents both from being absorbed into the blood stream and later transferred to the kidneys. Urinary oxalate may be more important to formation of calcium-oxalate kidney stone crystals than is the urinary calcium.

However it must be quickly noted here that calcium supplements increase kidney stone risks according to the Annuals of Internal Medicine, March 1997. High normal dietary calcium reduces kidney stones by 35 percent, but high calcium from non-foods - like calcium supplements - actually increase the risk of kidney stones by 20 percent. Those with the highest consumption of potassium, from eating fruits and vegetables, have half the risk of stones. A high fluid intake is associated with a 29 percent lower risk, while those who eat the most animal protein have a 33 percent higher risk of developing kidney stones.

Winning the battle with kidney stones is a two-stage war. The first hurdle - which is sometimes elected to be skipped by doctors and patients - is to become stone free to reduce later stone formation due to the presence of those existing stone crystals. Then the second hurdle is to eliminate (or at least reduce) the risk factors that might lead to formation of new kidney stones.

Copied from The Kidney Stone Website written by Roger Baxter revised by Lakes Area Urology 2/99