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Posted: 10:11 AM Nov 4, 2006
Preventing Kidney Stones
Research is promising New research into one of the causes of kidney stones could lead to new ways to prevent them.
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New research into one of the causes of kidney stones could lead to new ways to prevent them.
Rick Krupinski is a busy magazine editor but his job is often interrupted by painful kidney stones.
“They can hit at any time," he says. "I consider them to be time bombs that are residing within my body.”
Now there's good news. University of Michigan scientists are getting closer to preventing those time bombs from forming in the first place. They’re studying the genes, nearly 3,700 in all, of a fuzzy-looking bacterium called proteus mirabilis.
Dr. Harry Mobley, Ph D. says, “It’s been known for many years that proteus mirabilis causes kidney stones. However, we’re now learning about the mechanism by which these stones form.”
The research team found that the bacterium assigns each of its hair-like projections to stick to a specific surface, including the bladder.
Mobley says, "It can form a biofilm on this surface and then these numbers, large numbers of bacteria, they can go on to produce kidney stones by this mechanism.”
Now the goal is to better understand how the bacterium colonizes in the urinary tract to cause kidney stones.
“Secondly, it’s to develop vaccines or therapeutics to prevent infections in that patient population that is susceptible to these infections,” Mobley says.
Richard Krupinski says, "It would mean that that constant worry that resides somewhere in my head would be gone. And that, that would be a wonderful thing.”
Infection from the bacterium can be treated with antibiotics. However, sometimes it sticks to the stones themselves and becomes encased inside, protecting itself from the antibiotics.
Fast Facts:
Kidney Stones
The kidneys are a pair of fist-sized organs near the middle of the back. Blood travels through the kidneys, where tiny networks of filters remove waste products and extra water. Each day, the kidneys process about 200 quarts of blood. The water and waste form urine, which flows into a collection chamber (the bladder) for eventual elimination by the body.
Kidney stones form when tiny crystals in the urine clump together and form a solid mass. Some stones may be tinier than a grain of sand and others may be the size of a pearl (or even larger). There are several types.
The most common type of kidney stone is composed of calcium along with oxalate or phosphate. The body uses calcium to build and maintain strong muscles and bones. Excess calcium is taken to the kidneys, where it is flushed out of the body in urine. However, some people have a tendency to retain the calcium in their kidneys, causing a build-up and eventual formation of a stone. About 75 to 80 percent of kidney stones are calcium stones.
Struvite stones can occur after a bacterial infection in the urinary system. The bacteria release a chemical that neutralizes the acid in urine and leads to the formation of kidney stones. Struvite stones account for about 10 to 15 percent of kidney stones.
A uric acid stone can form when there is too much acid in the urine. About 9 to 10 percent of kidney stones are uric acid stones.
The least common kidney stone is made of cystine, an amino acid used to build muscles and nerves. Cystine doesn’t dissolve in urine. If too much builds up in the urinary tract, cystine stones can form. They account for about one percent of all kidney stones.
Researchers say about 12 percent of American men and 5 percent of women develop a kidney stone in their lives. Some people have more than one episode. According to the National Kidney and Urologic Diseases Information Clearinghouse, kidney stones were the reason for 2.7 million visits to physician offices and 600,000 visits to emergency rooms in 2000.
In some cases, kidney stones don’t cause any problems and eventually pass through the urinary system and out of the body. If the stone is large enough, or becomes stuck in the urinary tract, it can cause irritation and pain. The pain may be sharp or cramping and felt in the kidneys or lower abdomen. Other symptoms may include nausea and vomiting, fever, chills, weakness, cloudy or foul-smelling urine or blood in the urine.
Bacterial Infection and Kidney Stones
Proteus mirabilis is a bacterium that is associated with urinary tract infections and development of some kidney stones. Elderly patients, those who require long-term urinary catheterization and patients with spinal cord injuries are most at risk for the infection.
Harry Mobley, Ph.D. (featured in story), a Microbiologist at the University of Michigan and his colleagues are studying the link between P. mirabilis and kidney stone formation. Melanie Pearson, Ph.D., is the first scientist to perform an in-depth analysis of the genome sequence of the P. mirabilis bacterium.
Pearson and her colleagues found the bacteria have hair-like projections that enable it to stick to tissue surfaces. The bacteria grow, forming a biofilm on the surface. When a stone starts to form, the bacteria can stick to the walls of the stone. Eventually, the stone can surround and encase the bacteria, protecting the bacteria from antibiotics used to treat the infection. Thus, infections can become chronic and difficult to eradicate.
The investigators hope to eventually find clues about how P. mirabilis causes kidney stones. In the future, researchers would also like to develop a vaccine or some other type of treatment that would prevent infection in high risk patients.
Web Resources
For general information on kidney stones:
