kidney stones, renal lithiasis, calcium oxalate, uric acid, cysteine, cystinuria, struvate, hyperuricemia,

Kidney Stones

Kidney Stones

One of the principles I teach is that being well is different than not being sick – much different. Being well is being free of disease. Far too often someone who is “not sick” is simply unaware that a disease process is present. One can have an advanced illness and not feel sick. Sickness is often only a matter of timing; one can feel fine one minute and be sick the next.

A kidney stone is an excellent example of this. Kidney stones are formed when substances that are filtered out of the body by the kidney come out of solution and form crystals. The process can be demonstrated by filling a container with salt water and allowing the water to evaporate. As water is lost and the solution becomes more concentrated salt crystals will form along the sides of the container.

Physicians use several terms when referring to kidney stones. These are simply descriptive Latin terms. Renal calculus literally means kidney stone. Nephrolithiasis means the condition of having a kidney stone (nephro – kidney, lith – stone, iasis – condition). As the name implies, a kidney stone occurs when a substance that should be dissolved in the urine comes out of solution and forms a crystal in the kidney. As long as a crystal remains in the kidney its presence is generally unrecognized. If a crystal leaves the kidney and begins moving toward the bladder, however, the individual who has the stone becomes painfully aware of its presence. Over the years I’ve seen many people who were in the process of passing a kidney stone. Most have described the pain as the most intense they’ve ever experienced. Women commonly report that the pain is greater than they experienced during labor.

To understand kidney stones it is helpful to understand the anatomy of the urinary system. Most individuals have two kidneys, which are located toward the back, just below the rib cage. The kidneys have several functions, but their primary job is to filter the blood. The filtering process removes waste products and balances levels of minerals in the bloodstream. The filtrate is what we call urine.

Urine passes from the kidneys to the bladder via tubes called ureters. Ureters are narrow and muscular, designed to serve as a conduit for liquid urine, not solid crystals. Urine is stored in the bladder until it is emptied.

The filtering tubes of the kidneys lead to a chamber that is called the pelvis of the kidney. The pelvis funnels urine into the ureter. Nearly all kidney stones form in the pelvis. As long as they remain there they rarely cause any symptoms. When a stone leaves the pelvis and enters the ureter, however, intense pain generally ensues.

The pain of a kidney stone is colicy in nature, meaning that it has peaks and valleys. It will become almost unbearable as the muscle wall of the ureter contracts in an attempt to move the stone toward the bladder. As the muscle relaxes the pain will ease or vanish, only to return as the ureter begins to contract once more.

Kidney stone pain typically begins high in the abdomen and moves lower as the stone progresses toward the bladder. As it nears the bladder junction the pain is felt in the genital area. If the stone successfully passes into the bladder the pain will immediately cease.

The absence of pain is not proof that the stone has passed, however. If the stone stops moving, the pain will often stop as well. If the pain was present in the upper or mid abdomen immediately before it disappeared it is likely that the stone is still lodged in the ureter. If the pain was present in the low abdomen or genital area before the pain stopped it is much more likely to have passed successfully.

It is important to recognize that different types of kidney stones occur, as each has a different cause and requires different measures for prevention or treatment. Stones that contain calcium in combination with oxalate, phosphate, or apatite are the most common, accounting for approximately 80 percent of all kidney stones. Most of the remaining stones are made up of uric acid. A few stones contain the amino acid cysteine while the rest are composed of struvite, an ammonia compound.

The most important measure in preventing kidney stones, regardless of type, is drinking optimum amounts of purified water. A common recommendation is to drink two quarts or more daily. I prefer that people pay attention to the character of their urine and drink enough water to keep the urine pale. This is because urine becomes darker as it becomes more concentrated. As urine becomes more concentrated substances are much more likely to precipitate out as crystals. When I ask a person to drink enough water to keep the urine pale, I commonly hear an objection that this is not possible because he or she is taking vitamins that cause the urine to turn yellow. It is true that certain B vitamins cause the urine to appear more yellow, but the urine should still be a pale straw yellow rather than a dark bright yellow.

The leading predisposing factor for calcium stones is a genetic tendency to excrete more calcium than usual in the urine. This is called hereditary hypercalciuria. Less common conditions are hyperparathyroidism, an over-production of parathyroid hormone, and a disease called renal tubular acidosis, in which the kidneys do not excrete acid appropriately.

While physicians generally recommend that dietary or supplemental calcium limitation in the prevention of calcium-containing kidney stones other measures are more effective. The most common form of calcium-containing stone is calcium oxalate. Oxalate is a substance that is found in certain foods and beverages. The principle dietary sources of oxalate are coffee, cola, tea, chocolate, nuts, wheat bran, spinach, beets, strawberries and rhubarb.

Limiting oxalate-containing foods and beverages is of some benefit, but it is far more effective to take magnesium with meals. When an adequate amount of magnesium is present it will bind with oxalate in the intestinal tract. Since magnesium oxalate is not well absorbed, most will pass harmlessly out of the body in the stool.

The same is true of calcium, when taken with meals. Physicians commonly recommend that calcium supplements be taken apart from meals because studies have shown that the overall absorption of calcium is greater when food is not present. I believe that this is a short-sighted approach to calcium supplementation. Yes, a portion of calcium taken with a meal will be retained in the stool as calcium oxalate. If, however, the oxalate had been absorbed, calcium would have bound to it in the body and have been passed out through the kidney. The net effect on body calcium is therefore the same. The only difference is that if calcium oxalate is formed in the intestinal tract, rather than in the body, the likelihood of developing a kidney stone will be significantly less.

Citrate is also helpful in preventing calcium stones. This is because citrate helps to alkalinize the urine, which helps keep calcium in solution. I have even seen citrate supplementation dissolve stones that have become lodged in a ureter to pass without surgery.

Potassium citrate is the most effective form of citrate in alkalinizing the urine. This is available either as a prescription or as an over-the-counter supplement.

Urocit-K is the most common brand of prescription-strength potassium citrate. It comes in two strengths, 5 meq (540 mg). and 10 meq (1080 mg). Over-the-counter potassium citrate capsules typically contain 270 mg.

The goal is to take enough potassium citrate to maintain a urine pH between 6 and 7. (Urine pH may be tested using the same pH paper that is used for checking saliva for body pH.) This usually requires one or two 10 meq prescription tablets or 4 to 8 over-the-counter capsules three times daily.

Uric acid stones occur when uric acid crystals form in the urine. When uric acid crystals form in joints the condition is called gout. Therefore gout and uric acid kidney stones are related in some cases. Uric acid kidney stones occur when the body is excreting higher than usual amounts of uric acid in the urine to compensate for an overproduction of uric acid in the body, when the urine is too concentrated to keep uric acid in solution, and when the urine is too acidic. Increased uric acid production can trigger gout, but gout can also occur when the urinary excretion of uric acid is low.

In some cases urinary uric acid levels are high because of genetic abnormalities. In others it is elevated because of poor dietary or beverage choices, disease states, or chemotherapy. The dietary culprit is a substance called purine.

Purine is found in all protein-containing foods, but only diets high in red meats and seafood have been shown to significantly increase the risk of gout or uric acid stones. One of the largest studies to look at the relationship of diet and gout, which one would expect to apply to uric acid kidney stones as well, was published in the New England Journal of Medicine in 2004. The researchers followed 47,150 men with no prior history of gout for twelve years. They found that those who ate the greatest amount of meat were 40 % more likely to experience gout than those who ate the lowest amount and that those who ate the most seafood were 50 % more likely than those who at the least to have a gouty attack. Interestingly, vegetables with a high purine content did not increase the risk.

It appears that the Wellness Diet (Colorful, edible at room temperature, unrefined, inclusive of whole grains, legumes and oils, varied, and with meat portions limited to the size of a standard deck of playing cards) is an ideal diet for prevention of uric acid stones.

It has been shown that cherries, strawberries, blueberries, and other red-blue berries help to lower uric acid production. (While strawberries do contain oxalate it would be nearly impossible to trigger an oxalate stone by eating strawberries alone.) A convenient way to obtain the benefit of these fruits on a regular basis is to drink four to six ounces of tart cherry juice daily.

Beer has been shown to increase uric acid levels. In the study group referenced above, men who drank two or more beers daily were 2 ˝ times more likely to have an attack of gout than non-drinkers. Two shots of alcoholic spirits increased the risk by 1 ˝, and two 4 oz glasses of wine did not show any increase in gouty episodes.

Uric acid stones are more common in people with obesity. Therefore, weight loss may improve the outlook for overweight individuals who are prone to form uric acid stones. Disorders in which there is an overproduction of red blood cells, white blood cells, or platelets increase the risk of uric acid stones, as do many chemotherapeutic agents.

Prevention of uric acid stones is remarkably similar to the prevention of calcium-containing stones. Drink enough water to keep the urine pale, take potassium citrate to make the urine more alkaline, lose weight if that is indicated, limit alcohol intake (particularly beer consumption), eat cherries or red-blue berries or drink tart cherry juice, and treat any underlying disease process.

Cysteine stones are caused by a rare genetic disorder and are, therefore, the rarest form of kidney stones. Individuals with cystinuria, however, can pass literally hundreds of stones. Since dietary cysteine comes almost exclusively from animal protein, a strict vegetarian or vegan diet can dramatically lessen the number of cysteine stones in susceptible individuals. The medical community has never endorsed this approach, but the only reason appears to be the prevailing attitude that diets low in animal products are too restrictive for people to follow. That has not been my experience.

Drinking enough pure water to keep the urine pale and keeping the urine pH above 7.5 are helpful in reducing the number of cysteine stones, just as in the case of calcium and uric acid stones. Lemonade is a good beverage for cysteine stone formers, as citric acid helps to dissolve cysteine stones. Eating citrus fruits such as oranges has also been shown to be helpful.

The final type of kidney stone is a struvite stone, which is sometimes referred to as an infection stone (infective lithiasis). Struvite stones are formed by bacteria that cause ammonium to be released in the urine. Ammonium binds with magnesium and phosphate to form a stone. Bacteria trapped within the stones continue to produce ammonium, causing the stones to grow. Struvite stones can fill the kidney. Because a large struvite stone looks like the antler of a deer on x-ray it is called a staghorn calculus.

Because of their size, struvite stones rarely pass into the ureter to cause pain. They can therefore go unnoticed for an extended period of time. Staghorn calculi and their associated bacteria can cause significant kidney damage and may even induce cancer.

Struvite stones must be removed, either surgically or by a procedure in which shockwaves are sent though the body to fragment the stone and cause it to pass. The infection must be treated or the stone will return. Eradication of the infection is difficult because the bacteria develop biofilms that are resistant to antibiotics and the body’s immune system. The role of biofilms in chronic infections and their management was the subject of the February 2005 issue.

No one who has suffered the pain of passing a kidney stone wants to go through the experience a second time. Anyone who has not had the experience should seek to avoid it. Adhering to the principles I have discussed will dramatically lessen the risk.

© 2007 Wellness Clubs of

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