Kidney stones
Renal calculi; Nephrolithiasis; Stones - kidney; Calcium oxalate - stones; Cystine - stones; Struvite - stones; Uric acid - stones; Urinary lithiasis
A kidney stone is a solid mass made up of tiny crystals. One or more stones can be in the kidney or ureter at the same time.
If you ever have severe pain in your belly or one side of your back that comes and goes suddenly, you may be passing a kidney stone. Let's talk about the painful condition of kidney stones. A kidney stone is a mass of tiny crystals in your kidney or urinary tract. Stones are quite common, and tend to run in families. They can form in weeks or months when your urine contains too much of certain substances. There are several kinds of kidney stones. Calcium stones are by far the most common kind. They often form in men between the ages of 20 to 30. Calcium can combine with other substances found in your food, like oxalate, phosphate, or carbonate, to form stones. Cystine stones can form in people who have cystinuria, a condition passed down through families in which stones are made from an amino acid called cystine. Struvite stones are found mostly in women who have urinary tract infections. These stones can grow very large and can block the kidney, ureter, or bladder. Uric acid stones are more common in men than in women. They can occur in people who have a history of gout or are going through chemotherapy. So, how do you know if you have kidney stones? Well, you may not have symptoms until the stone move down the ureter tubes through which urine empties into your bladder. When this happens, the stones can block the flow of urine out of your kidneys. The main symptom is severe sharp pain that starts suddenly, usually in your belly or one side of your back, and it may go away just as quickly. Other symptoms can include abnormal urine color, blood in your urine, fever, chills, nausea, and vomiting. So, what do you do about kidney stones? Well, your health care provider will perform a physical exam. You may need blood tests, kidney function tests, and tests that look for crystals in your urine. Several imaging tests, like a CT scan, can see stones or a blockage in your urinary tract. Treatment will depend on the type of stone you have, and how bad your symptoms are. Small kidney stones that are less than 5 mm in diameter will usually pass on their own. You should drink at least 6 to 8 glasses of water per day to produce a large enough amount of urine to help bring the stone out. Pain can be pretty bad when you pass a kidney stone, so your doctor may prescribe pain medicines to help as well as medications that will help the stone pass. Other medicines can decrease stone formation or help break down and remove the material that is causing you to make stones. You may need surgery if the stone is too large to pass, the stone is growing, or the stone is blocking your urine flow. Kidney stones are painful, but you can usually pass them without causing permanent harm. However, kidney stones often come back, so you and your doctor will need to work on finding the cause of your stone. Lastly, delaying treatment can lead to serious complications, so if you think that you have kidney stones see your doctor right away.
The kidneys are responsible for removing wastes from the body, regulating electrolyte balance and blood pressure, and the stimulation of red blood cell production.
This is the typical appearance of the blood vessels (vasculature) and urine flow pattern in the kidney. The blood vessels are shown in red and the urine flow pattern in yellow.
Before we talk about how kidney stones are formed, take a moment to become familiar with the urinary tract. The urinary tract includes the kidneys, ureters, bladder, and urethra. Now let’s enlarge a kidney to get a closer view. Here’s a cross-section of the kidney. Urine flows from the outer cortex to the inner medulla. The renal pelvis is the funnel through which urine exits the kidney and enters the ureter. As urine passes through the kidneys, it can become very concentrated. When the urine becomes too concentrated, calcium, uric acid salts, and other chemicals dissolved in the urine can crystallize, forming a kidney stone, or renal calculus. Usually the calculus is the size of a small pebble. But ureters are very sensitive to being stretched, and when stones form and distend it, the stretching can be very painful. Often, people may not know they have kidney stones until they feel the painful symptoms resulting from a stone being stuck anywhere along the urinary tract. Fortunately, small stones typically pass out of the kidneys and through the ureters on their own, without causing any problems. However, stones can become more problematic when they block the flow of urine. Doctors call this one a staghorn kidney stone, and it is obstructing the entire kidney. Fortunately, these stones are the exception rather than the rule.
Kidney stones result when urine becomes too concentrated and substances in the urine crystalize to form stones. Symptoms arise when the stones begin to move down the ureter causing intense pain. Kidney stones may form in the pelvis or calyces of the kidney or in the ureter.
Extracorporeal shock wave lithotripsy (ESWL) is a procedure used to shatter simple stones in the kidney or upper urinary tract. Ultrasonic waves are passed through the body until they strike the dense stones. Pulses of sonic waves pulverize the stones, which are then more easily passed through the ureter and out of the body in the urine.
Cystinuria is a disorder characterized by cystine stones in the kidney, ureter, and bladder. A genetic abnormality results in abnormal transport of amino acids in the kidney. The high levels of the amino acid cystine in the urine lead to stone formation. While this disease only accounts for 1% to 2% of urinary tract stones in the general population, it is the most common cause among children.
A kidney stone is a solid piece of material that forms in a kidney. Kidney stones may be the size of sand or gravel, as large as a pearl, or even larger. A stone can block the flow of urine and cause great pain.
Causes
Kidney stones are common. Some types run in families. They may occur at any age, including in premature infants.
There are different types of kidney stones. The cause depends on the type of stone.
Stones can form when urine contains too much of certain substances that form crystals. These crystals can develop into stones over weeks or months.
- Calcium stones are most common. They are most likely to occur in men between ages 20 to 30. Calcium can combine with other substances to form the stone.
- Oxalate is the most common of these substances. Oxalate is present in certain foods such as spinach. It is also found in vitamin C supplements. Diseases of the small intestine increase your risk for these stones.
Calcium stones can also form by combining with phosphate or carbonate.
Other types of stones include:
- Cystine stones can form in people who have cystinuria. This disorder runs in families. It affects both men and women.
- Struvite stones are mostly found in men or women who have repeated urinary tract infections. These stones can grow very large and can block the kidney, ureter, or bladder.
- Uric acid stones are more common in men than in women. They can occur with gout or after receiving chemotherapy for some types of cancer.
- Other substances, such as certain medicines, also can form stones.
The biggest risk factor for kidney stones is not drinking enough fluids. Kidney stones are more likely to occur if you make less than 1 liter (32 ounces) of urine a day.
Symptoms
You may not have symptoms until the stone moves down the tube (ureters) through which urine empties into your bladder. When this happens, the stone can block the flow of urine out of the kidneys, causing pain.
The main symptom is severe pain that starts and stops suddenly:
- Pain may be felt in the belly area or side of the back.
- Pain may move to the groin area (groin pain), testicles (testicle pain) in men, and labia (vaginal pain) in women.
Other symptoms can include:
Exams and Tests
Your health care provider will perform a physical exam. The belly area (abdomen) or back might feel sore.
Tests that may be done include:
- Blood tests to check calcium, phosphorus, uric acid, and electrolyte levels
- Kidney function tests
- Urinalysis to check for crystals and red blood cells in urine
- Examination of the stone to determine the type
Stones or a blockage can be seen on:
- Abdominal CT scan
- Abdominal x-rays
- Kidney ultrasound
- Retrograde pyelogram
Treatment
Treatment depends on the type of stone and the severity of your symptoms.
Kidney stones that are small most often pass through your system on their own.
- Your urine should be strained so the stone can be saved and tested.
- Drink at least 6 to 8 glasses of water per day to produce a large amount of urine. This will help the stone pass.
- Pain can be very bad. Over-the-counter pain medicines (for example, ibuprofen and naproxen), either alone or along with narcotics, can be very effective.
Some people with severe pain from kidney stones need to stay in the hospital. You may need to get fluids through an IV into your vein.
For some types of stones, your provider may prescribe medicine to prevent stones from forming or help stones pass through your urinary system. These medicines can include:
- Allopurinol (for calcium oxalate or some uric acid stones)
- Antibiotics (for struvite stones)
- Phosphate solutions
- Potassium citrate
- Water pills (thiazide diuretics)
- Tamsulosin to relax the ureter and help the stone pass
Surgery is often needed if:
- The stone is too large to pass on its own.
- The stone is growing.
- The stone is blocking urine flow and causing an infection or kidney damage.
- The pain cannot be controlled.
- If there is a urinary tract infection or fever.
Today, most treatments are much less invasive than in the past.
- Lithotripsy is used to remove stones slightly smaller than one half an inch (1.25 centimeters) that are located in the kidney or ureter. It uses sound or shock waves to break up stones into tiny fragments. Then, the stone fragments leave the body in the urine. It is also called extracorporeal shock-wave lithotripsy or ESWL.
- Procedures performed by passing a special instrument through a small surgical cut in your skin on your back and into your kidney or ureters are used for large stones, or when the kidneys or surrounding areas are incorrectly formed. The stone is removed with a tube (endoscope).
- Ureteroscopy may be used for stones in the lower urinary tract. A laser is used to break up the stone.
- Rarely, open surgery (nephrolithotomy) may be needed if other methods do not work or are not possible.
Talk to your provider about what treatment options may work for you.
You will need to take self-care steps. Which steps you take depend on the type of stone you have, but they may include:
- Drinking extra water and other liquids
- Eating more of some foods and cutting back on other foods
- Taking medicines to help prevent stones
- Taking medicines to help you pass a stone (anti-inflammatory drugs, alpha-blockers)
Outlook (Prognosis)
Kidney stones are painful, but most of the time can be removed from the body without causing lasting damage.
Kidney stones often come back. This occurs more often if the cause is not found and treated.
You are at risk for:
- Urinary tract infection (UTI)
- Kidney damage or scarring if treatment is delayed for too long
Possible Complications
Complications of kidney stones may include the obstruction of the ureter (acute unilateral obstructive uropathy).
When to Contact a Medical Professional
Contact your provider if you have symptoms of a kidney stone:
- Severe pain in your back or side that will not go away
- Blood in your urine
- Fever and chills
- Vomiting
- Urine that smells bad or looks cloudy
- A burning feeling when you urinate
If you have been diagnosed with blockage from a stone, passage must be confirmed either by capture in a strainer during urination or by follow-up x-ray. Being pain free does not confirm that the stone has passed.
Prevention
If you have a history of stones:
- Drink plenty of fluids (6 to 8 glasses of water per day) to produce enough urine.
- You may need to take medicine or make changes to your diet for some types of stones.
- Your provider may want to do blood and urine tests to help determine the proper prevention steps.
References
American Urological Association website. Medical management of kidney stones (2019).
American Urological Association website. Surgical management of stones: AUA/Endourology Society guideline (2016).
Bushinsky DA. Nephrolithiasis. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 111.
Miller NL, Borofsky MS. Evaluation and medical management of urinary lithiasis. In: Partin AW, Dmochowski RR, Kavoussi LR, Peters CA, eds. Campbell-Walsh-Wein Urology. 12th ed. Philadelphia, PA: Elsevier; 2021:chap 92.
Version Info
Last reviewed on: 3/31/2024
Reviewed by: Sovrin M. Shah, MD, Associate Professor, Department of Urology, The Icahn School of Medicine at Mount Sinai, New York, NY. Review provided by VeriMed Healthcare Network. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.
