Patient education: Kidney stones in adults (Beyond the Basics)

KIDNEY STONE OVERVIEW — Kidney stones (also called nephrolithiasis or urolithiasis) are common, affecting approximately 1 in 5 males and 1 in 10 females 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.

This article will discuss kidney stones in adults. Kidney stones in children are discussed separately. (See "Patient education: Kidney stones in children (Beyond the Basics)".)

HOW KIDNEY STONES DEVELOP — A kidney stone can form when high levels of certain substances (calcium, oxalate, cystine, or uric acid) are present in the urine. Stones can also form when these substances are at normal levels, especially if you are not making a lot of urine (eg, not drinking enough fluids). The substances form tiny crystals, which become anchored in the kidney and gradually increase in size, forming a kidney stone. A stone can remain in the kidney for years or decades without causing any symptoms or damage to the kidney.

Typically, the stone will eventually 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 procedure to remove them.

KIDNEY STONE RISK FACTORS — Certain diseases, dietary habits, or medications can increase your risk of developing kidney stones; these are listed in the table (table 1). A family history of kidney stones may also increase your risk. Once you have had a kidney stone, you are at an increased risk of getting another one in the future.

KIDNEY STONE SYMPTOMS — Sometimes, a kidney stone does not cause any symptoms and is only found when imaging tests are done for another reason. Stones can remain in the kidneys for years without ever causing symptoms. However, stones typically do cause symptoms when they pass from the kidneys through the urinary tract.

Pain — Pain is the most common symptom when passing a kidney stone. Most often, pain only occurs with obstruction, which is when a stone blocks or impedes the passage of urine from the kidney to the bladder (figure 1). Pain can range from a mild ache to discomfort that is so intense it requires treatment in the hospital. Typically, the pain fluctuates in severity but does not go away completely without treatment. 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, and the pain can move toward the groin.

If you have pain that you suspect may be due to a kidney stone, call your health care provider for advice. They can do an examination, order tests, and recommend treatment if needed. If your pain is severe and you are not able to contact your provider, go to the emergency department for evaluation.

Blood in the urine — Most people with kidney stones will have blood in the urine; the medical term for this is "hematuria." The urine may appear pink or reddish, or the blood may not be visible until a urine sample is examined under a microscope. If you notice blood in your urine, let your health care provider know; they can order tests to figure out if it is caused by a kidney stone or something else. (See "Patient education: Blood in the urine (hematuria) in adults (Beyond the Basics)".)

Gravel — Some patients may pass "gravel" or "sand," which are multiple small stones in your urine.

Other symptoms — Other kidney stone symptoms may include nausea or vomiting, pain with urination, and an urgent need to urinate.

KIDNEY STONE DIAGNOSIS — Kidney stones are usually diagnosed based upon your symptoms, a physical examination, and imaging tests.

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 CT) is often recommended if kidney stones are suspected because it is the best way to see a stone. Plain X-rays cannot reliably detect kidney stones in all situations.

While "low-dose" CT scans involve less radiation than traditional CT scans, doctors still try to limit the number of CT scans a person has (in order to minimize radiation exposure).

Ultrasound — An ultrasound (or sonogram) is another type of imaging test. It can also be used to detect kidney stones, although small stones or stones in the ureters (the tubes that connect the kidney to the bladder) may be missed. Ultrasound is the preferred diagnostic procedure for people who should avoid radiation exposure, including pregnant women and children.

KIDNEY STONE TREATMENT — Treatment of a kidney stone that is causing obstruction depends upon the size and location of the stone, as well as your pain level and ability to keep down fluids. If your stone is small enough to be likely to pass, your pain is tolerable, and you are able to eat and drink, your health care provider will likely suggest treatment at home.

If you have severe pain or nausea, you will need to be treated with stronger pain medications and intravenous (IV) fluids, which are often given in the hospital. If you have a fever, you will also need treatment in the hospital as soon as possible, as this could indicate a potentially serious infection.

Home treatment — Managing a kidney stone at home involves treating your pain as needed, taking medication to help the stone pass more quickly (if your health care provider recommends this), and straining your urine so that the stone can be saved for testing once it does pass.

Pain relief — You can take non-prescription pain medication until the stone passes. This includes over-the-counter nonsteroidal antiinflammatory drugs (NSAIDs) such as ibuprofen (sample brand names: Advil, Motrin) or naproxen (sample brand names: Aleve, Naprosyn), but it is important to check with your doctor first. People with certain health conditions should not take NSAIDs.

Facilitating stone passage — There are several different medications that can shorten the time until passage of a kidney stone, such as tamsulosin (brand name: Flomax). Depending on your situation and the size of your stone, your provider may recommend taking one of these medications for several weeks, until the stone passes. Note that these medications do not cause the stone to pass immediately; it still may take several days or longer.

Straining your urine — You will probably be asked to strain your urine to recover the stone. After you retrieve it, you should bring it to your health care provider so it can be analyzed in a laboratory. Knowing what type of kidney stone you have is important in planning treatments to prevent future stones. (See 'Preventing future kidney stones' 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 if your stone does not pass on its own; your health care provider will likely refer you to a specialist called a "urologist" who can discuss your options with you and recommend the best approach for your situation.

Ureteroscopy — Ureteroscopy is a common procedure that uses a thin telescope, which is passed through the urethra and bladder, into the ureter and kidney (figure 1). This allows the doctor to see the stone and remove it or to break it 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.

Shock wave lithotripsy (SWL) — This procedure involves directing high-energy shock waves toward the stone. These sound waves pass through the skin and internal body 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.

Shock wave lithotripsy is a reasonable option for many people who need help breaking up a stone. Lithotripsy is particularly good for stones 1 cm or less in the kidney and upper ureter. Shock wave lithotripsy is not effective for treating large or hard stones. You may require medication to make you sleepy and reduce pain during this treatment, although this depends upon the type of equipment used.

Percutaneous nephrolithotomy (PNL) — This is a minimally invasive surgical procedure in which a small telescope is passed through the skin of the back and into the kidney to remove the stone. Very large or complex stones, or large stones that do not respond to shock wave lithotripsy (see 'Shock wave lithotripsy (SWL)' above) or ureteroscopy, may need to be removed this way.

Asymptomatic stones — If you have a kidney stone that was identified on an imaging test but is causing no symptoms, you may or may not need to have it removed right away. This decision is based upon the size and location of your stone, as well as your ability to get treatment 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), your health care provider is more likely to advise that you have the stone removed.

PREVENTING FUTURE KIDNEY STONES — After you have had a kidney stone, you are more likely to have another one in the future. Your health care provider will evaluate whether you may have certain health problems that increase your risk of kidney stones (table 1). This may include:

●Analysis of passed stones – If you have passed and saved one or more stones (see 'Straining your urine' above), they should be analyzed to determine the composition (eg, calcium oxalate, uric acid, etc).

●Urine tests – Your provider may request that you perform a 24-hour urine collection; this involves saving all the urine you produce over a 24-hour period, which then gets analyzed at the laboratory. (See "Patient education: Collection of a 24-hour urine specimen (Beyond the Basics)".)

●Other tests – Your provider may also recommend additional tests (eg, blood or imaging tests) if an underlying condition is suspected.

Depending on what your provider thinks may have caused your kidney stone, they may suggest doing one or more of the following to lower your risk of having another stone in the future:

●Increasing fluid intake – Drinking more fluids can help lower your risk of kidney stones. 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. While you can vary the types of beverages you drink, sugar-sweetened beverages (such as soda and sports drinks) actually seem to increase the risk of kidney stones; they have other negative health effects as well and should therefore be avoided.

●Changing your diet – You may be advised to make changes in your diet; this will depend upon the type of kidney stone you have and results of your 24-hour urine collection tests.

●Preventive medication – You may be advised to take a medication to reduce the risk of future stones.

WHERE TO GET MORE INFORMATION — Your health care 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 website (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 education: Kidney stones in adults (The Basics)
Patient education: Kidney stones in children (The Basics)
Patient education: Polycystic kidney disease (The Basics)
Patient education: Abdominal pain (The Basics)
Patient education: 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 education: Kidney stones in children (Beyond the Basics)
Patient education: 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.

Cystinuria and cystine stones
Kidney stones in adults: Diagnosis and acute management of suspected nephrolithiasis
Kidney stones in adults: Kidney stones during pregnancy
Nephrolithiasis in renal tubular acidosis
Kidney stones in adults: Surgical management of kidney and ureteral stones
Kidney stones in adults: Struvite (infection) stones
Kidney stones in adults: Prevention of recurrent kidney stones
Kidney stones in adults: Epidemiology and risk factors
Kidney stones in adults: Evaluation of the patient with established stone disease
Kidney stones in adults: Uric acid nephrolithiasis

The following organizations also provide reliable health information.

●National Library of Medicine

     (www.nlm.nih.gov/medlineplus/healthtopics.html)

●National Institute of Diabetes and Digestive and Kidney Diseases

     (www.niddk.nih.gov)

●National Kidney Foundation

     (www.kidney.org)