Kidney Stones: An Overview
Kidney stones are one of the most painful conditions a person can have, and they are one of the most common disorders of the urinary tract. In 2000, patients made 2.7 million visits to their healthcare providers for problems associated with kidney stones, and more than 600,000 patients went to the emergency room for kidney stone problems.
However, kidney stones are not a product of modern life. Scientists have found evidence of kidney stones in a 7,000-year-old Egyptian mummy.
Although most kidney stones pass out of the body without any intervention by a physician, kidney stones that cause symptoms and other complications can be treated.
Kidney Stones: Understanding the Urinary Tract
The urinary tract system consists of the kidneys, ureters, bladder, and urethra. The kidneys are two bean-shaped organs located below the ribs toward the middle of the back. The role of the kidneys is to:
- Help make red blood cells
- Remove extra water and wastes from the blood (wastes come from the normal breakdown of active muscle and from the food that you eat)
- Convert the extra water and wastes from the blood to urine.
If your kidneys do not remove these wastes, they will build up in the blood and damage your body.
Narrow tubes called ureters carry urine from the kidneys to the bladder, which is an oval-shaped chamber in the lower abdomen. Like a balloon, the bladder's elastic walls stretch and expand to store urine, and flatten back together when the urine is emptied through the urethra outside of the body.
A kidney stone is a solid piece of material that forms in the kidney out of crystals in the urine. The crystals normally remain tiny enough to travel through the urinary tract and out of the body in the urine without being noticed. This is because urine contains chemicals that prevent or inhibit the crystals from forming.
However, these inhibitors do not seem to work for everyone. In some people, the crystals stick together and continue to build up to form kidney stones.
A kidney stone may stay in the kidney or break loose and travel down the urinary tract. However, a large kidney stone may get stuck in a ureter, the bladder, or the urethra -- which would block the flow of urine and cause great pain.
For unknown reasons, the number of people in the United States with kidney stones has been increasing over the past 30 years, from 3.8 percent in the late 1970s to 5.2 percent in the late 1980s and early 1990s. Scientists believe that the increase may be related to diet and lifestyle.
Caucasians are more prone to developing kidney stones than African Americans, and the condition affects more men than women. The prevalence of kidney stones rises dramatically as men enter their 40s and will continue to rise into their 70s. For women, the prevalence of kidney stones will peak in their 50s. Once a person gets one kidney stone, other kidney stones are likely to develop.
What Do Kidney Stones Look Like?
Kidney stones may be as small as a grain of sand or as large as a golf ball. They may be smooth or jagged, and they are usually yellow or brown.
Kidney stones may contain various combinations of chemicals. The four most common types of kidney stones contain:
- Calcium
- Struvite
- Uric acid
- Cystine.
The most common type of stone contains calcium in combination with either oxalate or phosphate. These calcium stones are called calcium oxalate stones or calcium phosphate kidney stones.
(Click Types of Kidney Stones for more information.)
No one knows the exact cause of kidney stones, and doctors can seldom explain why one person will get kidney stones and another person will not. However, research has shown that people with certain risk factors are more likely than others to develop the condition. (A risk factor is anything that increases a person's chance of developing a disease.)
Kidney stones risk factors include:
- Age
- Gender
- Certain diets
- Family history
- Urinary tract infections and blockage of the urinary tract
- Inherited diseases, such as cystinuria, hyperoxaluria, hypercalciuria, hyperuricosuria
- Kidney disease, such as cystic kidney diseases
- Medical conditions, like gout
- Excess vitamin D intake
- Metabolic disorders, such as hyperparathyroidism
- Medications, such as diuretics, indinavir, or calcium-based antacids.
Symptoms of Kidney Stones
Kidney stones often do not cause any symptoms. However, symptoms, if apparent, can include:
- Sharp, cramping pain in the back, side, or groin
- Nausea
- Blood in urine (urine will appear pink)
- Frequent urination or urge to urinate
- Urine that smells bad or looks cloudy
- A burning feeling when you urinate
- Fever
- Chills
- Vomiting.
In order to diagnose a patient with kidney stones, doctors will typically:
- Gather a medical history
- Ask about the patient's occupation
- Ask about the patient's eating habits
- Order laboratory tests, which will include urine and blood tests.
The laboratory should also analyze any stones that are removed from a patient, because the composition of the stones may help in treating kidney stones.
Treatment for Kidney Stones
Most kidney stones will pass out of the body as fluid intake is increased; pain medication may also be prescribed. However, if you have a stone that will not pass through your body, your doctor may need to perform a procedure to get rid of it. In the past, the only way to remove a problem stone was through major surgery. However, doctors now have new treatment options for problem kidney stones. These options include:
- Extracorporeal shock wave lithotripsy (ESWL)
- Ureteroscopy
- Percutaneous nephrolithotomy (tunnel surgery).
Once the kidney stone has passed or been removed, your doctor will tell you how to prevent future kidney stones. These preventative options can include lifestyle changes and/or medicine, depending on the type and cause of the kidney stones.
(Click Kidney Stones Treatment for more information.)
Kidney Stones in Women and Children
Although men tend to develop kidney stones more frequently than women, the number of women with kidney stones has been increasing. Children may also develop kidney stones, although this does not occur very often. Most children with kidney stones usually have a genetic or metabolic disease that makes them more likely to form stones.
Other Names for Kidney Stones
Urolithiasis is the medical term used to describe kidney stones that occur in the urinary tract. Other frequently used terms are urinary tract stone disease and nephrolithiasis. Doctors also use terms that describe the location of the kidney stone in the urinary tract. For example, a ureteral stone (or ureterolithiasis) is a kidney stone found in the ureter.
Key information to keep in mind regarding kidney stones includes:
- Most kidney stones will pass out of the body without a doctor's help
- See your doctor if you have severe pain in your back or side that will not go away
- See your doctor if you have blood in your urine (urine will appear pink)
- Drink lots of water to prevent more kidney stones from forming
- When you pass a kidney stone, try to catch it in a strainer to show to your doctor
- Talk to your doctor about how to avoid more kidney stones.
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