Kidney stones: A very common problem in the United States
A Nephrologist’s Perspective
In the year 2000, over 2 million office visits in the U.S. were for the primary diagnosis of kidney stones, also known as nephrolithiasis. The incidence of kidney stones is rising in the country, and by the age of 70, up to 16% of men and 8% of women will have at least one symptomatic stone. Men are twice as likely to form kidney stones than women, though this difference has decreased over the past two decades. As primary care physicians and consultants, we must do a better job to increase the awareness of this problem and help not just in the treatment of kidney stones, but in their prevention also.
Over 80% of all kidney stones contain calcium, usually in the form of calcium oxalate. Other types of stones include calcium phosphate, uric acid, struvite and cystine. The chemical composition of urine, analyzed with a 24-hour sample, can give important clues as to the risk factors for stones, and thus, allow for risk reduction with medications and other dietary and lifestyle changes. This is typically managed by nephrologists and urologists. Although many urologists do manage this aspect of kidney stone care, their primary role is in the surgical management of stones that are not passed with conservative management. As such, nephrologists play a vital role in the primary and secondary prevention of kidney stones.
Chronic medical conditions such as obesity, gout, and hypertension can increase the risk of stone formation. Diet and type / amount of fluid intake play a vital role also. Typically, a low salt diet (less than 2 grams daily) and high water intake (over 3 liters daily) is the cornerstone of any prevention strategy. Personal or family history of kidney stones, along with certain medical conditions and medications are all risk factors for kidney stone formation.
The diagnosis of kidney stones is based on history taking and physical examination. Imaging studies can help confirm the diagnosis, and may include ultrasonography, X-ray or CT scan. Once diagnosed, treatment involves pain control and medications that can help increase the odds of passing the stone. It is very unlikely that a stone will pass spontaneously if larger than 1cm. Obstructive stones, of course, can impair kidney function, either reversibly or irreversibly depending on various other factors and the duration of obstruction. Patients are typically instructed to strain their urine for several days, and bring the stone into the office for analysis. Again, consultation with a nephrologist is important in the “team” management of kidney stones.
Water and lemonade are good options in terms of beverages to drink to increase fluid intake. Sodas can increase the risk of stone formation and should be avoided. Decreased fluid intake and eating a diet high in salt and fats are very common risk factors for forming stones. Thus, it should come as no surprise that the areas with the highest prevalence of kidney stones in this country tend to have the highest rates of obesity, hypertension and diabetes.
Today is a good day to take control of your kidney health!