KIDNEY STONES OVERVIEW
Kidney stones (also called nephrolithiasis or urolithiasis) affect approximately 1 in 11 people (19 percent of men and 9 percent of women by age 70 years). Fortunately, treatment is available to effectively manage most stones. In addition, you can take steps to prevent kidney stones from recurring.
A detailed review of kidney stones in children is available separately. (See "Patient information: Kidney stones in children (Beyond the Basics)".) More detailed information about kidney stones is available by subscription. (See "Diagnosis and acute management of suspected nephrolithiasis in adults".)
HOW KIDNEY STONES DEVELOP
A kidney stone can form when substances such as calcium, oxalate, cystine, or uric acid are at high levels in the urine. Stones can also form if these substances are at normal levels, especially if the amount of urine made each day is low. The substances form crystals, which become anchored in the kidney and gradually increase in size, forming a kidney stone.
Typically, the stone will move through the urinary tract (figure 1) and is passed out of the body in the urine. A stone may cause pain if it becomes stuck and blocks the flow of urine. Large stones do not always pass on their own and sometimes require a minimally invasive surgical procedure to remove them.
KIDNEY STONE RISK FACTORS
Certain diseases, dietary habits, or medications can increase your risk of developing kidney stones (table 1).
KIDNEY STONE SYMPTOMS
Pain — Pain is the most common symptom of kidney stones. Pain can range from a mild and barely noticeable ache to discomfort that is so intense it requires treatment in the hospital. Typically, the pain gets worse and better, but does not go away completely. Waves of severe pain, known as renal colic, usually last 20 to 60 minutes. Pain can occur in the flank (the side, between the ribs and the hip) or the lower abdomen (figure 1).
Blood in the urine — Most people with kidney stones will have blood in the urine (hematuria). The urine may be pink or reddish, or the blood may be visible only with urine dipstick testing or microscopic examination of the urine. (See "Patient information: Blood in the urine (hematuria) in adults (Beyond the Basics)".)
Gravel — You may pass "gravel" or small stones in your urine.
Other symptoms — Other kidney stone symptoms include nausea or vomiting, pain with urination, and an urgent need to urinate.
Asymptomatic kidney stones — Many people with kidney stones have no symptoms (asymptomatic means without symptoms). These kidney stones are usually found when an imaging study (such as an ultrasound, x-ray or CT scan) is performed for other purposes. Stones can remain in the kidneys for many years without ever causing symptoms. (See "The first kidney stone and asymptomatic nephrolithiasis in adults".)
KIDNEY STONE DIAGNOSIS
Kidney stones are usually diagnosed based upon your symptoms, a physical examination, and imaging studies.
Computed tomography (CT) scan — A CT scan creates a three dimensional image of structures within the body. A particular type of CT scan (called noncontrast helical CT) is often recommended if kidney stones are suspected.
Ultrasound — An ultrasound (or sonogram) can also be used to detect kidney stones, although small stones or stones in the ureters (kidney tubes) may be missed. However, ultrasound is the procedure of choice for people who should avoid radiation, including pregnant women and children.
KIDNEY STONE TREATMENT
Treatment of kidney stones depends upon the size and location of your stone, as well as your pain and ability to keep down fluids. If your stone is likely to pass, your pain is tolerable, you are able to eat and drink, and you can be treated at home.
If you have severe pain or nausea, you will need to be treated with stronger pain medications and IV fluids, which are often given in the hospital. In addition, patients with stones and who also have a fever should be treated in the hospital as soon as possible to avoid a life-threatening infection. (See "Options in the management of renal and ureteral stones in adults".)
Home treatment — You can take non-prescription pain medication until the stone passes. This includes nonsteroidal antiinflammatory drugs such as ibuprofen (Advil, Motrin) or naproxen (Aleve).
Other medications, such as tamsulosin (Flomax®), may also be recommended to speed the passage of stones.
You will probably be asked to strain your urine to recover the stone; it can then be analyzed in a laboratory to determine the content of the stone (eg, calcium, uric acid, etc). Knowing what type of kidney stone you have is important in planning treatments to prevent future stones (see 'Kidney stone prevention' below).
If the stone does not pass — Stones larger than 9 or 10 millimeters rarely pass on their own and generally require a procedure to break up or remove the stone. Some smaller stones also do not pass. Several procedures are available.
Shock wave lithotripsy (SWL) — Lithotripsy is the treatment of choice in many patients who need help passing a stone. Lithotripsy is particularly good for stones 1 cm or less in the kidney and upper ureter. Lithotripsy is not effective for treating large or hard stones. You may require medication to make you sleepy and reduce pain during lithotripsy treatment, although this depends upon the type of lithotripsy equipment used.
Lithotripsy is done by directing high-energy shock waves toward the stone. These sound waves pass through the skin and bodily tissues and release energy at the stone surface. This energy causes the stone to break into fragments that can be more easily passed in the urine.
Percutaneous nephrolithotomy (PNL) — Extremely large or complex stones, or stones resistant to shock wave lithotripsy, may require a minimally invasive surgical procedure to remove the stone. In this procedure, small endoscopic (telescopic) instruments are passed through the skin (percutaneously) into the kidney to remove the stone.
Ureteroscopy — Ureteroscopy is another type of endoscopic procedure that uses a thin scope, which is passed through the urethra and bladder, into the ureter and kidney. This endoscope allows the urologist to see the stone and remove it, or to break it up into smaller pieces that can pass more easily. Ureteroscopy is often used to remove stones blocking the ureter, and sometimes for small stones in the kidney.
Treatment of asymptomatic stones — If you have a kidney stone that is causing no symptoms, you may or may not need to remove the stone. The decision is based upon the size and location of your stone, as well as your ability to be treated quickly if symptoms were to develop. If there is a chance that you would not be able to get treatment quickly (eg, if you travel frequently), you are more likely to need to have the stone removed.
Regardless of the decision to treat or not, you should be evaluated for underlying health conditions that can increase the risk of kidney stones (table 1).
KIDNEY STONE PREVENTION
After you have a kidney stone, you should have blood and urine tests to determine if you have certain health problems or dietary issues that increase the risk of kidney stones (table 1).
If you passed and saved the stone, it should be analyzed to determine the type of stone. In addition, your clinician may request that you perform a 24-hour urine collection (all the urine you make over a 24-hour period) to determine underlying risk factors for your kidney stone disease. (See "Patient information: Collection of a 24-hour urine specimen (Beyond the Basics)".)
Based upon these test results, one or more of the following may be recommended:
- You may be given a medication to reduce the risk of future stones.
- You may be advised to drink more fluids to decrease the risk of another stone. The goal is to increase the amount of urine that flows through your kidneys and also to lower the concentrations of substances that promote stone formation. Experts recommend drinking enough fluid that you make more than 2 liters of urine per day.
- You may be advised to make changes in your diet; the changes recommended will depend upon the type of kidney stone you have.
- A kidney stone can form when there are normal or high levels of certain substances in the urine. These substances can form crystals. Crystals become attached to the kidney and gradually increase in size, forming a stone.
- Eventually, the stone moves through the urinary tract and is passed in the urine. Or, the stone can remain in the urinary tract, blocking urine flow, which can cause pain.
- Certain diseases and habits can affect a person's risk for developing kidney stones. These include a past history or family history of kidney stones, certain dietary habits, underlying medical problems, certain medications, and dehydration (table 1) (see 'Kidney stone risk factors' above).
- The most common symptom of a kidney stone is pain; other symptoms include hematuria (blood in the urine), passing gravel, nausea, vomiting, pain with urination, and an urgent need to urinate. Many patients with kidney stones have no symptoms (see 'Kidney stone symptoms' above).
- Testing is usually needed to diagnose a kidney stone. Computed tomography (CT scan) is the preferred test for most patients (see 'Kidney stone diagnosis' above).
- Treatment usually includes pain medication and increased fluids (to drink) until the stone is passed. Over the counter pain medication (eg, ibuprofen) may be helpful. If the pain is not controlled, a stronger medication (narcotic) may be needed. In addition, certain medications may be prescribed to increase the likelihood of stone passage (ie, tamsulosin) (see 'Home treatment' above).
- Small stones (less than 5 millimeters) usually pass without treatment. Larger stones (9 millimeters or greater) rarely pass on their own. Treatment for larger stones is usually done in a hospital (see 'If the stone does not pass' above).
- Further testing is recommended for patients with recurrent kidney stones or in first-time stone formers who may be at risk for additional stone formation. Tests help to determine if an illness is causing kidney stones to form. Medications may be prescribed to prevent future stones. Drinking more fluids and changing the diet can help to prevent future kidney stones (table 1) (see 'Kidney stone prevention' above).
WHERE TO GET MORE INFORMATION
Your healthcare provider is the best source of information for questions and concerns related to your medical problem.
This article will be updated as needed on our web site (www.uptodate.com/patients). Related topics for patients, as well as selected articles written for healthcare professionals, are also available. Some of the most relevant are listed below.
Patient level information — UpToDate offers two types of patient education materials.
The Basics — The Basics patient education pieces answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials.
Patient information: Kidney stones in adults (The Basics)
Patient information: Kidney stones in children (The Basics)
Patient information: Polycystic kidney disease (The Basics)
Patient information: Acute abdomen (belly pain) (The Basics)
Patient information: Hydronephrosis in adults (The Basics)
Beyond the Basics — Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are best for patients who want in-depth information and are comfortable with some medical jargon.
Patient information: Kidney stones in children (Beyond the Basics)
Patient information: Blood in the urine (hematuria) in adults (Beyond the Basics)
Professional level information — Professional level articles are designed to keep doctors and other health professionals up-to-date on the latest medical findings. These articles are thorough, long, and complex, and they contain multiple references to the research on which they are based. Professional level articles are best for people who are comfortable with a lot of medical terminology and who want to read the same materials their doctors are reading.
Clinical significance of residual stone fragments following stone removal
Diagnosis and acute management of suspected nephrolithiasis in adults
Evaluation of the adult patient with established nephrolithiasis and treatment if stone composition is unknown
Management of struvite or staghorn calculi
Management of ureteral calculi
Nephrolithiasis during pregnancy
Nephrolithiasis in renal tubular acidosis
Options in the management of renal and ureteral stones in adults
Pathogenesis and clinical manifestations of struvite stones
Prevention of recurrent calcium stones in adults
Renal complications of extracorporeal shock wave lithotripsy
Risk factors for calcium stones in adults
The first kidney stone and asymptomatic nephrolithiasis in adults
Uric acid nephrolithiasis
The following organizations also provide reliable health information.
- National Library of Medicine
- National Institute of Diabetes and Digestive and Kidney Diseases
- National Kidney Foundation