Anyone who has ever passed a kidney stone will not forget the experience. It can be excruciatingly painful. The incidence of kidney stones has been increasing in recent decades, perhaps because of diet choices and relative lack of fluids.
Not all kidney stones cause symptoms, however, and many are discovered when X-rays are obtained to evaluate for an unrelated condition. Also, they may be discovered when someone is evaluated after finding blood in the urine. The pain develops when a kidney stone breaks loose and begins to work its way from the kidney toward the bladder through the connecting tube (ureter).

Kidney stones usually develop when the urine becomes too concentrated, allowing minerals and other urinary substances to form crystals on the inner surfaces of the kidneys. Over time, these crystals may combine to form a small, hard mass, or stone. Although most small kidney stones pass down to the bladder without causing any permanent damage, it's important to determine the underlying cause so that more stones can be avoided in the future.

Stones form within the collecting system of the kidney. Many remain there indefinitely. Some stones break free into the urine and are propelled downward toward the bladder by the smooth muscle contractions of the ureter. These tube-like structures become narrower as they approach the bladder, making blockage by the stone possible even for relatively small stones.

Symptoms...

One will not have signs and symptoms unless a kidney stone is large, causes a blockage, is causing infection or is being passed. The most common symptom is an intense cramping pain that can fluctuate in intensity over periods of five to 15 minutes. The pain usually starts in the back or side just below the edge of the ribs. As the stone moves down the ureter, the pain may radiate to the lower abdomen, groin and genitals. If the stone stops moving, the pain may stop too.
Other signs and symptoms may include:

• Bloody, cloudy or foul-smelling urine
• Nausea and vomiting
• Persistent urge to urinate
• Fever and chills if an infection is present

Causes...

The crystals that lead to kidney stones are more likely to form when your urine contains a high concentration of certain substances — especially calcium, oxalate, uric acid and rarely, cystine. They may also form because of a low level of substances that help prevent crystal formation, such as citrate and magnesium. Crystals also may form if the urine becomes too concentrated or is too acidic or too alkaline.
A number of factors can cause changes in urine, including the heredity, diet, drugs, climate, lifestyle factors and a variety of medical conditions. Each of the main types of kidney stones has a different cause:

• Calcium stones make up about four out of five kidney stones. They are usually made up of a combination of calcium and oxalate, a compound that occurs naturally in some fruits and vegetables. A number of factors can cause high concentrations of these in urine. Excess calcium, from ingesting large amounts of vitamin D, from treatment with thyroid hormones or certain diuretics, or from some cancers can lead to stones. Also, high levels of calcium will develop if the parathyroid glands, which regulate calcium metabolism, are overactive (hyperparathyroidism). Certain genetic factors, intestinal bypass surgery and a diet high in oxalic acid may cause excess amounts of oxalate as well.
• Struvite stones are found more in women than in men, and are almost always the result of chronic urinary tract infections. Bacterial enzymes increase the amount of ammonia in the urine, which is incorporated in the crystals of struvite stones. These stones are often large, may have a characteristic stag's-horn shape and can cause serious damage to the kidneys.
• Uric acid stones are formed of a byproduct of protein metabolism. These are more likely to develop in someone who has undergone chemotherapy, who eats a high-protein diet or who has certain predisposing genetic factors.

Risks...

These factors may increase your risk of developing kidney stones:

• Lack of fluids- produces a higher concentration of substances that can form stones.
• Family or personal history.
• Age, sex and race- Most people who develop kidney stones are between 20 and 70 years of age; men are affected more than women and white Americans more than black Americans.
• Certain diseases- Rare, inherited diseases such as renal tubular acidosis and cystinuria can increase the risk of kidney stones. Also, more common disorders like gout, chronic UTIs and hyperparathyroidism can add to risk.
• Certain medications- Diuretics may increase your risk of developing kidney stones in some situations and decrease it in others.
• Diet- A diet that's high in protein and low in fiber can increase risk of some types of kidney stones.
• Limited activity- People who are bedridden or very sedentary for a long period of time may release more calcium from their bones, increasing the risk for stones.

Diagnosis...

Although occasionally found during a routine medical exam, most kidney stones are diagnosed when person complains of severe kidney pain, chronic urinary tract infections or blood in the urine. If the doctor thinks you have kidney stones, he'll likely order a blood test to look for excess calcium or uric acid in the blood. He will also likely order a 24-hour collection of urine to check to see if you're excreting too many stone-forming minerals or too few inhibiting substances.
You may also have one or more of the following imaging tests:

• Abdominal X-ray- this will visualize most kidney stones and can help to judge changes in the size of a stone over time.
• Ultrasound- this technique combines high-frequency radio waves and computer processing to view your internal organs. It's safe and noninvasive, but may miss small stones.
• Intravenous pyelography (IVP)- this study can be useful in determining the location of stones and can define the degree of blockage a stone causes. A contrast dye is injected into a vein and a series of X-rays is taken as the dye moves through the kidneys, ureters and bladder. IVP has largely been replaced by the computerized tomography (CT) scan.
• Spiral CT scan- this imaging test has become the standard of care for evaluating kidney stones. It can be performed rapidly and identify stones regardless of composition.
• The doctor may ask a patient to urinate through a strainer so that any stone can be recovered and analyzed. The appropriate treatment and preventive plan going forward will depend on knowing what type of kidney stone the patient has.

Treatment...

Treatment for kidney stones varies, depending on the type of stone and the cause. Some stones will pass on their own by having the patient drink plenty of water and stay physically active. Stones that can't be treated conservatively, (because of bleeding, kidney damage or infection), may need professional treatment. Procedures include:

• Shock wave lithotripsy (SWL). This treatment uses shock waves to break the stones into tiny pieces that are then passed.
• Percutaneous nephrolithotomy. When SWL isn't effective, or the stone is very large, the urologist may remove the kidney stone through a small incision in the back using an instrument called a "nephroscope."
• Ureteroscopic stone removal. This procedure may be used to remove a stone lodged in a ureter. The stone is grabbed with a small instrument (ureteroscope) that's passed into the ureter through your bladder.

Prevention...

Kidney stones can often be prevented by having the patient make a few lifestyle changes. If these measures aren't effective and blood and urine tests reveal a correctable chemical imbalance, the doctor may prescribe certain medications.

Lifestyle changes

• Drink about 3.5 quarts (14 cups) of fluids every day.
• If stones are calcium oxalate, restrict foods rich in oxalates. These include meats, chicken, fish (such as herring and anchovies), asparagus, berries, chocolate, and cooked spinach.
• Restricting intake of calcium doesn't seem to lower your risk. An exception to this rule occurs when an individual absorbs too much dietary calcium from the intestine. In such a circumstance, restricting calcium intake is useful. Calcium supplements seem to have the same protective effect as dietary calcium, but only if they're taken with meals.

Medications (based upon stone type)

• Calcium stones- a thiazide diuretic or a phosphate-containing preparation.
• Uric acid stones- allopurinol (Zyloprim, Aloprim) will reduce uric acid levels in the blood and urine.
• Struvite stones- long-term use of antibiotics in small doses may be useful to prevent recurring infection.
• Cystine stones- these are the hardest stones and the most difficult to treat. Certain medications to alkalinize the urine or to bind the cystine in the urine may help when combined with extremely high urine output.