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A kidney stone is a solid piece of material that forms from crystallization of excreted substances in the urine. The stone may remain in the kidney or break loose and travel down the urinary tract. A small stone may pass all of the way out of the body, but a larger stone can get stuck in a ureter, the bladder, or the urethra. This may block the flow of urine and cause great pain.
A kidney stone may be as small as a grain of sand or as large as a pearl, and some are as big as golf balls. Approximately 80 percent of kidney stones are less than 2 centimeters in width. They may be smooth or jagged, and are usually yellow or brown in color.
Kidney stones are one of the most painful disorders, and one of the most common disorders of the urinary tract. It is estimated that about a million people in the United States are treated for kidney stones each year. Consider the following statistics:
- Caucasians are more prone to kidney stones than are African-Americans.
- Although stones occur more frequently in men, the number of women who develop kidney stones has been increasing.
- Kidney stones strike most people between the ages of 20 and 40.
- Once a person develops more than one stone, he/she is more likely to develop additional stones.
A kidney stone develops from crystals that separate from urine and build up on the inner surfaces of the kidney. Normally, urine contains chemicals that prevent or inhibit the crystals from forming. However, in some people, stones still form. Crystals that remain small enough will travel through the urinary tract and pass out of the body in the urine without even being noticed.
- calcium stones
Calcium stones are the most common type of stones. Calcium is a normal part of a healthy diet and is used by bones and muscles. Calcium not used by the body goes to the kidneys where it is normally flushed out with the rest of the urine. In some people, however, the calcium that stays behind joins with other waste products to form a stone.
- struvite stones
Struvite stones are a type of stone that contains the mineral magnesium and the waste product ammonia. It may form after an infection in the urinary system.
- uric acid stones
Uric acid stones may form when there is too much acid in the urine.
- cystine stones
Cystine stones consist of cystine, one of the building blocks that make up muscles, nerves, and other parts of the body, can build up in the urine and form a stone. Cystine stones are rare. The disease that causes cystine stones (cystinosis) runs in families.
The following are the most common symptoms of kidney stones. However, each individual may experience symptoms differently. Symptoms may include:
- extreme, sharp pain in the back or side that will not go away
- blood in the urine
- nausea and vomiting
- cloudy or odorous urine
- frequent urination
- a burning feeling when you urinate
- fever and chills
Prompt medical attention for kidney stones is necessary.
The symptoms of kidney stones may resemble other conditions or medical problems. Always consult your physician for a diagnosis.
In addition to a complete medical history and physical examination, diagnostic procedures for kidney stones may include the following:
- intravenous pyelogram (IVP) - a series of x-rays of the kidney, ureters, and bladder with the injection of a contrast dye into the vein - to detect tumors, abnormalities, kidney stones, or any obstructions, and to assess renal blood flow.
- urinalysis - laboratory examination of urine for various cells and chemicals, such as red blood cells, white blood cells, infection, or excessive protein.
- blood tests - laboratory examination of the blood to detect substances that might promote stone formation.
- renal ultrasound - a non-invasive test in which a transducer is passed over the kidney producing sound waves which bounce off of the kidney, transmitting a picture of the organ on a video screen. The test is used to determine the size and shape of the kidney, and to detect a mass, kidney stone, cyst, or other obstruction in the kidney.
Specific treatment for kidney stones will be determined by your physician based on:
- your age, overall health, and medical history
- extent of the disease
- your tolerance for specific medications, procedures, or therapies
- expectations for the course of the disease
- your opinion or preference
Some kidney stones pass out of the body without any intervention by a physician. In cases that cause lasting symptoms or other complications, kidney stones may be treated with various techniques, including the following:
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- shock waves or extracorporeal shock wave lithotripsy (ESWL) - use of a machine to send shock waves directly to the kidney stone to break a large stone into smaller stones that will pass through the urinary system. There are two types of shock wave machines: with one machine, the patient sits in a tub of water, with the other, the patient lies on a table.
- ureteroscope - a long wire with a camera attached to it is inserted it into the patient's urethra and passed up through the bladder to the ureter where the stone is located. A cage is used to obtain the stone and remove it.
- tunnel surgery (Also called percutaneous nephrolithotomy.) - a small cut is made in the patient's back and a narrow tunnel is made through the skin to the stone inside the kidney. The physician can remove the stone through this tunnel.
According to the National Institute of Diabetes and Kidney Diseases, the best ways to prevent kidney stones are the following:
- Drink more water. Up to 12 full glasses of water a day can help to flush away the substances that form stones in the kidneys. Ginger ale, lemon-lime sodas, and fruit juices are acceptable.
- Limit coffee, tea, and cola to one or two cups a day. The caffeine may cause a rapid loss of fluid.
- Consult your physician regarding dietary modifications.
- Medications may be prescribed to prevent calcium and uric acid stones from forming.
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Online Resources of Kidney and Urinary Disorders