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What Are They?
Stones form in the urinary system when there is too much of a certain type of crystal in the urine. Substances that would stop this crystal from forming are reduced or missing from the urine. Certain proteins (the framework for crystal deposits) are present in the urine. Several factors enable the stones to form in the urinary system. These include genetics, hormonal imbalances, environmental factors, diet and body abnormalities that lead to chronic infection. People who do not drink enough water are at risk. They become dehydrated, creating only a small amount of concentrated urine. This can add to the risk of forming a certain type of stone.
How Common Are Stones in the Urinary System?
In the United States alone, an estimated 240,000 to 720,000 people (or between 0.1 and 0.3% of the population) will suffer a stone event each year. Between 12 and 24 million Americans will develop a stone some time during their lives. The four most common stones are ones:
- Containing calcium
- Caused by infection
- Created from uric acid
- Made up from cystine
Types of Stones
Calcium-containing stones are the most common. In the United States, 70% of all stones found contain calcium. This includes calcium-oxalate, calcium phosphate or both.
Infection-caused stones (magnesium ammonium phosphate or struvite) account for 15 to 20% of all stones.
Uric acid stones make up five to 10 percent of all stones.
Cystine stones are very rare and are found in only one to five percent of all cases.
Symptoms will vary, depending on the stone's size and where it is. Generally, the patient will experience colic or intense pain that starts in the lower back and wraps around to the front and down into the groin area. Patients describe shooting pains. Colic is often compared to the labor pains experienced during childbirth. One similarity is that the pains come and go. Patients may also note blood in the urine and painful or difficult urination. Some patients may also run a fever.
There are several tools used to diagnose stones in the urinary system. The specific tool used will differ, depending on the type of stone. The tools may include:
- Urinalysis: A small amount of urine is collected into a cup. A brief initial test can be done in the office to see if there is an infection or invisible blood in the urine. A laboratory will do a more detailed test, and the results are usually available in about 48 hours.
- Ultrasound: An ultrasound is done in the office. Most people are familiar with the ultrasound used to learn whether a baby will be a girl or a boy. Using the same equipment on the kidney, the physician can tell if stones or cysts are present.
- KUB: This is an X-ray of the kidney, ureters and bladder. A KUB will only show stones that are visible with the radiation of an X-ray.
- Intravenous Pyelogram (IVP): This is a type of X-ray that is done after a dye is injected into the body. The dye provides a sharp contrast on the film. Anything blocking the urinary system can be identified this way.
- Computed Tomography (CT): This uses a small X-ray beam. During scanning, thin slices through the body are recorded. The process is repeated in consecutive slices. The slices are later put together by computers to produce a cross-sectional image. A CT can be used for diagnosis and planning surgery.
URS - Ureteroscopic Stone Fragmentation and Removal
RIRS - Retrograde Intrarenal Surgery
PCNL- Percutaneous Nephrolithotripsy
Laser Vaporization - of stones of the bladder or urethra
The best ways to prevent stones are to eat a low sodium diet and increase how much you drink. You should be drinking about 16 ounces of water every hour that you are awake and cut back on carbonated and caffeinated drinks. Additional prevention depends on the type of stone that is formed.
Patients with Calcium-Oxalate Stones (75% of all urinary calculi in the United States): Increasing fluids is one of their most important preventative measures. Low urine volume clearly raises their risk of stones. While there is little scientific evidence to support cutting back or eliminating calcium from their diet, eating fewer foods with oxalate is reasonable. This includes tea, nuts, strawberries and some green leafy vegetables (such as kale). Eating less salt and fat and more dietary fiber is also helpful. In general, a healthy diet is a stone-prevention diet.
Patients with Uric Acid Stones (5 to 10% in the United States): Extra attention must be paid to their fluid intake. They must increase the fluids they drink to produce a large amount of urine. They also must maintain proper alkalinization of the urine, as their urine pH tends to be low. Proper urinary alkalinization is usually managed with oral medication. Additionally, they should limit how much protein they eat.
Patients with Struvite (Infection) Stones (15 to 20% in the United States): They are twice as likely to be women as men. Women have more urinary tract infections, which makethem susceptible to stone formation. Struvite stones are difficult to treat, and sterilization of the urine is a necessary part of treatment. Once the stones are removed, the patient must be followed carefully to avoid more urinary tract infections.