Kidney stones at a glance
- Kidney stones are hard “pebbles” of accumulated salts and minerals that form in the kidneys, in the bladder or anywhere in the urinary tract.
- Smaller stones can pass through the urinary tract on their own; larger stones may need to be removed by a physician.
- Some kidney stones pass without symptoms, others cause severe pain, but kidney stones usually do not cause lasting damage.
- Kidney stones may be made of several different minerals, which affect how a physician treats the stones.
What are kidney stones?
Kidney stones are small “pebbles” of salts and minerals. They may form in the kidneys or in any part of the urinary tract, which includes the kidneys, the bladder and the urethra (the tube that carries urine out of the body.)
Unfortunately, kidney stones are very common. Men experience kidney stones slightly more frequently than women do.
Some kidney stones are as small as a grain of sand. Others grow as large as a golf ball. Smaller kidney stones may pass relatively easily.
Passing them can be extremely painful. Each year, more than half a million people visit an emergency department because of kidney stone pain. Usually, people only know they have kidney stones because of the pain.
People can pass small stones by drinking a lot of water and perhaps taking over-the-counter pain medication. Stones that are stuck in the urinary tract or cause complications may need to be removed by surgery. Most kidney stones do not cause any long-term effects.
It is important that people who believe they may have passed a kidney stone see a physician. Kidney stones have a few risks. They can raise the risk of urinary tract infections (UTIs) and kidney damage. If a patient passes a stone at home, he or she should save it and ask a doctor if the stone should be tested.
Causes of kidney stones
Most kidney stones form when the urine composition changes. In this case, the body does not process calcium or other salts and minerals properly.
Being dehydrated (not drinking enough water) can create a bodily condition where minerals and salts clump together, causing stones to form. People who live in a hot or dry climate, or who exercise a lot, might be more likely to get kidney stones.
Other risk factors for kidney stones include:
- Personal or family history. Kidney stones may run in families. People who have had one kidney stone are more likely to have additional kidney stones.
- Certain medical conditions and surgery. Personal medical conditions or procedures (listed below) that change the digestive process can make kidney stones more likely.
- Crohn’s disease
- Inflammatory bowel disease
- Gastric bypass surgery
- Chronic diarrhea
- Urinary tract infections (UTIs)
- Renal tubular acidosis (acid accumulation)
- Hyperparathyroidism (excess of parathyroid hormone)
- Cystinuria (genetic defect inhibiting amino acid reabsorption)
- Taking certain medications.
- Eating a diet high in protein and salt. Consuming too much salt makes the kidneys filter more minerals, which increases the chance of kidney stones.
Types of kidney stones
People experience different types of kidney stones. Each type is made of different minerals. Doctors will probably try to determine what type of stone the patient has because each type of stone has a different cause. Knowing the type can help manage the risk of having another kidney stone.
Kidney stones form from these minerals:
- Calcium stones are the most common and are usually made of calcium oxalate. Oxalate is a substance in food, including some fruits, vegetables, nuts and chocolate. Calcium or oxalate may be increased in the urine because of
- Large doses of vitamin D
- Having had gastric bypass surgery
- A metabolic disorder
Calcium phosphate forms some calcium stones.
- The hereditary disorder cystinuria causes some people’s kidneys to produce too much of the cystine amino acid, which can cause cystine stones.
- Some infections, such as UTIs, can cause struvite stones, which can grow rapidly and may become very large.
- Uric acid.The body’s breakdown of purines found in food results in uric acid, which is usually passed through the kidneys and expelled in urine. Gout, a high-protein diet, dehydration and certain genetic conditions can cause uric acid stones.
There are other types of kidney stones, but they do not occur very often.
Symptoms of kidney stones
Most people who have a kidney stone discover it because of the pain. They usually feel sharp cramps in the back, side, lower abdomen or groin. People also may have nausea and vomiting.
This pain occurs when a kidney stone has moved within the urinary tract. Pain caused by a kidney stone may change, moving to a different spot or getting more severe as the stone moves through the urinary tract.
Patients experiencing the following symptoms of a possible kidney stone should call a doctor:
- Abdominal or groin pain that is severe, comes in waves or gets better and worse
- Severe pain in the side and back, below the ribs
- Painful urination
- Urine that is cloudy, smells foul, or is pink, brown or red
- Needing to urinate persistently and urinating very often or only small amounts.
More severe symptoms call for seeking medical attention immediately. These symptoms include:
- Blood in urine
- Very severe pain (you can’t sit still or be comfortable enough to relax)
- Nausea and vomiting along with the pain
- Fever and chills (a sign of infection)
- Being unable to urinate.
Kidney stones that are in the kidney or bladder may not cause any symptoms. A doctor might discover these stones while diagnosing another condition. Or they may begin to cause symptoms if they move through the urinary system.
It is also a good idea to see a physician to rule out other conditions that have similar symptoms. These conditions include hernias, prostatitis, appendicitis and ectopic pregnancy.
Diagnosing kidney stones
Many people learn they have kidney stones after they visit their doctor or emergency room because of pain in the back, side or belly. To diagnose kidney stones, a physician will do an examination and several tests. These tests may include:
- Analyzing passed stones. Patients who pass a stone should bring it to their physician. Patients might be asked to urinate through a strainer to catch other stones. The lab will analyze these stones to learn why stones are forming. This can help physicians make a plan to help prevent additional stones.
- Urine testing. Physicians may order a 24-hour urine collection test. Analysis of the urine can show if a person’s body is excreting too many minerals that form stones, or too few substances that keep stones from forming.
- Blood tests. Blood tests will check for uric acid and calcium in the blood. If results are high, physicians may want to check for other medical conditions.
- Imaging or scans. These tests visually check for kidney stones and their location. Imaging options include x-rays, ultrasounds and computerized tomography (CT) scans.
Treatment of kidney stones
Various treatments for kidney stones are available. Any stone that becomes stuck in the urinary tract, or is too large to pass, may need a doctor’s treatment. Those treatments are described here. Individual treatment will depend on the type of stone and its cause.
Many kidney stones can be managed at home. A person passing a kidney stone at home may need to:
- Drink water and other fluids. Unless a physician tells the patient otherwise, drinking up to 2-3 quarts daily may help the stone pass through the urinary system.
- Take pain medicine. Talk to a physician about the options.
- Take a medication prescribed by a physician that will help the stone pass.
Preventing kidney stones
There are several things a person can do to help prevent kidney stones, the most important is to drink enough water. It may help patients to visualize dissolving the salts, calcium and minerals in their body, like salt dissolving in a glass of water.
Patients should aim to drink 8-10 glasses of water, or even more, each day. If a person’s urine is very light yellow or nearly clear, he or she is drinking enough.
Learn more about the treatment and prevention of kidney stones.