Kidney stones

Kidney stones are a common medical condition affecting about five percent of the general U.S. population.  

The kidneys are located in the mid-back of the abdomen.  They are responsible for the maintaining the body’s fluid and electrolyte balance, as well as eliminating unwanted waste products filtered from the blood.  The kidneys empty into the urinary bladder via the ureters.  

The development of a kidney stone begins as a microscopic crystallization of minerals (calcium, phosphate, oxalate and uric acid).  Over time, these deposits can grow larger.  Stones that remain in the kidney may go unnoticed for some time.  But, as a stone moves out of the kidney and into the ureters, it begins to cause problems.  

Since the ureters are so small, stones that enter these tubes can cause irritation of their lining, spasms and severe pain as they move toward the bladder.  Sharp pains can be felt in the back and side and may radiate toward the groin.  Blood in the urine, painful urination, nausea, vomiting, fever and chills can be present.  

The larger the stone, the harder it is to pass.  90 percent of stones that are less than five millimeters in diameter will eventually pass through the ureter.  Stones one centimeter in diameter or greater have a less than 10 percent chance of passing and may obstruct the ureter.

Diagnosing a kidney stone involves obtaining clinical information from the patient and urine testing to see if there is visible or microscopic blood in the urine.  Since a majority of kidney stones are composed of calcium (70 to 80 percent), they can be seen on a regular X-ray.  If the stones are not seen on a plain X-ray, a CT scan of the abdomen will identify most kidney stones and can determine if there is any blockage in the ureter.    

Treatment is to get the stone out of the urinary system.  If the stone is small enough, flushing it out with lots of oral fluids usually will be effective.  Controlling pain as the stone passes is also necessary.    

If the stone is unlikely to pass on its own, special urological procedures may be needed.  Lithotripsy is a means of breaking up the stone into smaller pieces using shock waves.  Another method is to retrieve the stone by going up through the ureter with a scope.

Men are twice as likely to get kidney stones as women.  Some stones also tend to be hereditary.  Other risk factors for developing stones include not drinking enough fluids each day and consuming high amounts of meats and sodium in the diet.  Certain types of bowel disease can also lead to stone formation.  Obesity is also an independent risk factor for stones, particularly in women.

Individuals who are at risk for getting kidney stones can take proactive steps to minimize their risk of getting another stone.  Drink lots of fluids each day.  A target of about two quarts of urine production per day is recommended.  Eat a low-salt (1,500 mg or less/day) and low-meat (two 6-8 oz. servings/day) diet with moderate calcium. 

Decreasing the intake of oxalates which are present in foods such as spinach, rhubarb, beets, chocolate, nuts, tea, strawberries, soy, and wheat bran may also be beneficial. 

Finally, weight loss can be desirable as well.

The content in this column is for informational purposes only.  Consult your physician for appropriate individual treatment.  Dr. Reynolds practices Family Medicine in Chesterfield.    

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