What is a kidney stone?
A kidney stone is a solid mass formed from substances in the urine. These substances are normally passed in your urine, but they can become highly concentrated and crystalize when there is not enough urine volume. This is typically a result of inadequate daily fluid intake. These stone-forming substances are:
These and other chemicals are the “waste products” that must exit the body.
Kidney stones usually range in size from as small as a grain of sand or gravel to the size of a chickpea. They can even be as large as golf balls. Smaller stones (those less than the size of a chickpea) can pass through the urinary tract on their own, but can be associated with significant pain. Depending on their size, you may or may not notice these stones. Larger stones can get trapped in the ureters (tubes which drain the urine from the kidney into the bladder). When this happens, the stones keep urine from exiting the body.
Blocking the flow of urine causes severe pain or bleeding. Stones that can’t pass on their own are treated with surgery. This decision is based on the stone size, number of stones/overall amount, locations, and other factors such as shape, type, and patient preference.
What are the most common types of kidney stones?
The most common type of kidney stone is a calcium oxalate stone. This type of stone happens when calcium and oxalate join in your urine. It can happen when you have high quantities of oxalate, low amounts of calcium and aren’t drinking enough fluids.
Stones caused by uric acid are also fairly common. These come from a natural substance called purine, which is the byproduct of animal proteins (meat, chicken and fish).
These types of kidney stone run in families, so talk to your healthcare provider about your family history.
How does a kidney stone pass through my urinary tract?
A kidney stone starts out in your kidney. It can stay there and build up for years. Some people may even have kidney stones in their kidney for long period of time without knowing it’s there. Once it leaves the kidney, the stone travels down the ureters towards the bladder. The kidney stone enters the bladder and then exits the body through the urethra. Small stones pass out of the body with your urine. Larger stones can get stuck along the way out of the body and may need treatment by your healthcare provider.
How long does it take to form a kidney stone?
You can actually have a kidney stone for years without knowing it’s there. Stones can slowly form over years. As long as these stones stay in place within the kidney, you won’t feel anything. Pain from a kidney stone typically starts as the stone moves out of the kidney to pass out of the body. Sometimes, a stone can form more quickly — in a few months. This is related to your risk factors and history of kidney stones. Your healthcare provider will discuss all of your risk factors and might do a 24-hour urine test to check how quickly you develop stones.
If I have multiple kidney stones, are they all made of the same substances?
Not all kidney stones are made of the same substances. The materials that make up a kidney stone can vary. You could develop a calcium oxalate stone once and then one made of uric acid another time. This change can happen throughout your life and can be due to things like the treatment you were given for your last stone or other medical conditions.
Who is most likely to experience kidney stones?
Caucasian men in their 30s and 40s have the highest incidence of kidney stones. However, anyone can develop kidney stones.
Symptoms and Causes
What are the risk factors for developing kidney stones?
Risks for developing kidney stones include:
There are several risk factors for developing kidney stones. These risks can include:
- Not drinking enough liquids.
- Having a diets that leads to increased excretion of any of the substances listed above.Having a family history of kidney stones.
- Having a blockage in the urinary tract.
Certain medical conditions can also increase your risk of developing a stone because you have higher or lower levels of the substances that make up a kidney stone. These conditions can include:
- Hypercalciuria (high calcium levels in the urine).
- High blood pressure.
- Kidney cysts.
- Cystic fibrosis.
- Parathyroid disease.
- Inflammatory bowel disease.
- Chronic diarrhea.
- Some surgical procedures, including weight loss surgery or other stomach/intestine surgeries.
There are medications that can increase your risk of developing a stone. These medications can include:
- Diuretics (“water pills”).
- Calcium-based antacids.
- Crixivan® (used to treat HIV infections).
- Topamax® and Dilantin® (used to treat seizures).
- Cipro® (ciprofloxacin).
- Ceftriaxone (antibiotics).
Certain foods can also place you at risk of a kidney stone. These foods include:
- Meats and poultry (foods high in animal proteins).
- Sodium (diets high in salt).
- Sugars (fructose, sucrose and corn syrup).
What are the signs and symptoms of kidney stones?
You can actually have a kidney stone in your kidney for years and not know it’s there. However, when it starts to move or becomes very large, you may start to feel a few symptoms. Symptoms of a kidney stone can include:
- Feeling pain in the lower back or side of body. This pain can start as a dull ache that may come and go. It can become severe and result in a trip to the emergency room.
- Having nausea and/or vomiting with the pain.
- Seeing blood in the urine.
- Feeling pain when urinating.
- Not being able to urinate.
- Feeling the need to urinate more often.
- Experiencing fever/chills.
- Having urine that smells bad or looks cloudy.
Smaller kidney stones may not cause pain or other symptoms. These small stones pass out of the body in your urine.
Diagnosis and Tests
How are kidney stones diagnosed?
Diagnosis of kidney stones starts with a physical exam and review of your medical history. Other tests include:
- Imaging tests: To see the size, shape and location of the stones. These tests determine the most suitable treatment, and sometimes are used to review the result of your treatment. Types of imaging tests used are X-rays, CT scan and ultrasound. Both X-ray tests and CT scans use a small amount of radiation to create their images.
- Blood test: To measure how well your kidneys are functioning, to look for signs of infection, and to look for biochemical problems that lead to forming kidney stones.
- Urine sample test: To look for signs of an infection and to examine the levels of the stone-forming substances — calcium, oxalate, urate, cystine, xanthine and phosphate.
A CT scan of the abdomen is an imaging test that creates a three-dimensional view of the organs within the abdominal cavity. Typically no contrast (or dye) is used for kidney stone diagnosis.. This test shows the stone size and location and conditions that may have caused the stone to form. In addition, the other organs within this area of the body can be evaluated.
An ultrasound of the urinary tract uses sound waves to detect kidney stones and indirect signs of kidney stones, such as changes in the kidney’s size and shape.
Management and Treatment
How are kidney stones treated?
Your treatment options for a kidney stone can vary on the size of the stone and where it is located in your urinary tract. Treatment options include:
- No treatment: Small stones may not need treatment if they can pass out of the body on their own or if they are not causing a blockage
- Medications: To relax the ureter to allow stones to pass.
- Minimally-invasive procedures: Procedure carried out by entering the body through a small incision in the skin or through the body’s natural openings.
No treatment. Sometimes kidney stones can pass through urine on their own depending on the size and location. Drinking plenty of liquids helps the kidney stones travel through the urinary tract. Passing the stone may take up to three weeks.
Medications. Severe pain, requiring an emergency room visit, can be managed with IV narcotics, IV anti-inflammatory drugs, and IV drugs to manage nausea/vomiting. Stones causing less pain can be managed with an anti-inflammatory drug such as ibuprofen. (Caution: Ask your doctor before taking ibuprofen. This drug can increase the risk of kidney failure if taken while having an acute attack of kidney stones – especially in those who have a history of kidney disease and associated illnesses such as diabetes, hypertension and obesity.) Other medications may be given to relax the ureter such as tamsulosin (Flomax®) or nifedipine (Adamant®, Procardia®) so that the stones can pass on their own.
- Ureteroscopy: To perform this procedure, a small instrument, called an ureteroscope, is inserted in the urethra, through the bladder, and into the ureter. This instrument allows stones to be seen and then retrieved in a surgical “basket” or broken apart using a laser. These smaller pieces of kidney stones are then more easily able to exit the body through the urinary tract.
- Shockwave lithotripsy: In this procedure, the patient is placed on a special type of surgical table or tub. High-energy shock waves are sent through water to the stone(s) location. The shock waves break apart the stones, which are then more easily able exit the body through the urinary tract.
- Percutaneous nephrolithotomy: When kidney stones can’t be treated by the other procedures – either because there are too many stones, the stones are too large or heavy, or because of their location — percutaneous nephrolithotomy is considered. In this procedure, a tube is inserted directly into the kidney through a small incision made in your back. Stones are then disintegrated by an ultrasound probe and suctioned out so that you do not have to pass any fragments. A urethral stent is placed after the procedure (an internal tube from the kidney to the bladder which is removed one week after surgery in the office). Patients are typically kept overnight for observation and discharged home in the morning.
- Open stone surgery: Open stone surgery, is rarely performed. It is currently only done in 0.3% to 0.7% of cases.
How long does it take to pass a kidney stone?
The amount of time it can take to pass a kidney stone varies. A stone that’s smaller than 4 mm may pass within one to two weeks. A stone that’s larger than 4 mm could take about two to three weeks to completely pass.
Once the stone reaches the bladder, the stone typically passes within a few days, but may take longer, especially in an older gentleman with a large prostate. However, pain may subside even if the stone is still in the ureter, so it is important to follow up with imaging if you do not pass the stone within 4-6 weeks.
Does cranberry juice help with kidney stones?
Though cranberry juice can help prevent urinary tract infections (UTIs), it doesn’t help kidney stones.
Does apple cider vinegar help with kidney stones?
Vinegar is acidic and it can sometimes create changes to your urine which helps stones. However, this doesn’t always help. Talk to your healthcare provider about the use of vinegar for kidney stones.
Does lemon juice help with kidney stones?
Lemon juice is rich is citrate, which can help prevent kidney stones from forming. Citrates are found in several citrus fruits, including:
How can kidney stones be prevented?
There are several ways to decrease your risk of kidney stones, including:
- Drinking more fluids, especially water. You should drink at least 64 ounces of liquids per day. Liquids help you stay hydrated. Staying hydrated helps you urinate more often, which helps “flush away” the buildup of the substances that cause kidney stones. If you sweat a lot from your activities, be sure to drink more water.
- Limiting the amount of salt (sodium) in your diet — the DASH diet might be recommended as a low-sodium option.
- Losing weight if you are overweight.
- Limiting the types of foods and drinks that led to the development of your specific type of kidney stone. You may be asked to collect your urine over a 24-hour period. Stone fragments and minerals in the urine can help identify what may have caused your kidney stone. Based on the stone’s content, another healthcare professional, a dietitian, can suggest changes in your diet to help decrease your risk of developing more stones.
- Taking medication prescribed by your doctor to help prevent kidney stones based on your specific stone type and any health problems that make you more likely to form a stone.
Should I cut calcium out of my diet if I develop calcium oxalate kidney stones?
If you develop kidney stones composed of calcium, you may be tempted to cut calcium out of your diet. However, this is actually the opposite of what you should do. If you have calcium oxalate stones, the most common type, it’s recommended that you have a diet higher in calcium and lower in oxalate. Foods that are high in oxalates include:
- Dried peas and beans.
- Nuts and nut butters.
- Wheat bran.
Foods that are high in calcium include:
- Cow’s milk.
- Calcium-fortified juices.
- Dried beans.
- Calcium-fortified hot cereal.
It’s also important to drink plenty of fluids to dilute to dilute the substances in your urine.
What other things can I eat or drink to prevent kidney stones?
There are certain foods and drinks might help prevent kidney stones from developing. These can include:
- Drinking plenty of fluids.
- Cutting back on your sodium.
- Increasing the amount of citrates you consume (lemon, lime, orange and melons all have citrates).
- Limiting the amount of oxalates you consume (these are found in foods like spinach, rhubarb, nuts and tea).
Talk to your healthcare provider about the best foods and drinks to prevent the development of future stones. Often, there will be certain foods that work for you but not for another person.
Should I drink soda and coffee if I have kidney stones?
There are some beverages that aren’t recommended if you have kidney stones, including soda. Sweetened and dark colas are linked to an increased risk of stone formation. You should also avoid drinks with sugar or corn fructose syrup.
However, coffee has been linked to a decreased risk of developing kidney stones. Studies have shown that people who drink coffee have fewer kidney stones.
Outlook / Prognosis
What is the outlook for kidney stones?
The outlook for kidney stones is very positive, although this is a risk of recurrence (the stones coming back). Many kidney stones pass on their own over time without needing treatment from your healthcare provider. Medications and surgical treatments to remove larger kidney stones are generally very successful and involve little recovery time.
It is possible to get kidney stones multiple times throughout your life. If you find you keep developing kidney stones, your healthcare provider may work with you to discover why the stones happen. Once the cause is found, you may be able to make lifestyle changes to prevent future stones from forming.
Can a large kidney stone cause an injury?
Your risk of injury from a kidney stone can go up based on the size and location of the stone. The size of the stone is important as it passes out of your body. A larger stone could get stuck in your ureter, causing pressure to build up. This can lead to renal failure and, in the worst case (but rare) scenario, you could lose your kidney. The chance of passing a 1 cm stone is less than 10%, and stones larger than 1 cm typically do not pass
How long does pain last after you pass a kidney stone?
Pain from a kidney stone can persist for a few days after completely passing a stone, and this can vary. If the pain persists beyond a week after passing a stone, repeat imaging (typically an ultrasound) is obtained to see if any further blockage is present (sometime due to a remaining stone fragment).