Kidney stones: types, causes, treatment and prevention

Kidney stones are a common problem around the world and their incidence appears to be increasing.

On this page: 

1. What are calcium stones? 
2. What are uric acid stones? 
3. What are cystine stones? 
4. What are struvite stones? 
5. What causes kidney stones? 
6. Signs and symptoms of kidney stones
7. Diagnosis of urinary stones
8. Treatment of kidney stones
9. How long does it take for a kidney stone to pass?
10. The stages of kidney stone passage
11. Medication and pain management
12. How to protect your body from kidney stones? 
13. What foods can cause kidney stones? 
14. Summary

Kidney stones are formed when certain dissolved minerals build up in the kidneys.

Low fluid intake and dietary factors may play a role in the development of kidney stones, which can lead to infections and kidney damage.

Kidney stones can be small and pass through the urinary tract unnoticed, but some grow to be larger than a ping pong ball.

Kidney stones are a common(1) problem among people, and dietary factors and climate change may be contributing to this increase. Kidney stones can be a painful medical problem.

The causes of kidney stones vary depending on the type of stone.

What are calcium stones?

Calcium stones are the most common(2) of the various types, and are often made of oxalates (calcium oxalate).

They can also be made of phosphates and malates (calcium phosphate, calcium malate).

Calcium oxalate may be caused by eating foods rich in oxalates, including(3):

• Spinach

• Peanuts

• Okra

• Potato chips

• Chocolate

Eating fewer of these foods can reduce your risk of developing this type of stone.

The main symptoms of calcium oxalate crystals in the urine are:

• Pain in the side and back that can be severe

• Pain when urinating

• Blood in the urine

• Cloudy, foul-smelling urine

• Nausea and vomiting

• Persistent, urgent need to urinate

However, although some kidney stones are made of calcium, getting enough calcium in your diet can prevent stones from forming.

What are uric acid stones?

This type of kidney stone is the second most common type. This type of stone develops(4) when your urine is too acidic.

Groups with risk factors for developing this type of stone include:

• People with gout

• People with diabetes

• People who are overweight or obese

• People with metabolic syndrome

The main factors that determine the formation of uric acid stones include(5):

• Low urine pH

• Low urine volume

• Excessive uric acid in the urine

Congenital disorders may lead to the formation of these stones, in addition to chronic diarrhea, hypovolemia, bone marrow proliferative disorders, and uric acid medications.

Uric acid stones may also develop with a diet high in animal protein.

A diet rich in purines may increase(6) the acidity of urine. Purine is a colorless substance found in animal proteins, such as fish, shellfish, and meat.

Therefore, it is recommended to avoid animal proteins in people with or who have risk factors for developing uric acid stones.

What are cystine stones?

Cystine stones are less common than the previous stones, with about 1 in 7,000 people worldwide developing cystine kidney stones.

The cause of formation in both men and women is usually due to people with a genetic disorder(7) called cystinuria.

Cystinuria doesn't cause symptoms unless you have a cystine stone. Symptoms may include(8):

• Blood in your urine

• Pain when you urinate

• Sharp pain in your side of the back, pelvis, and abdomen

• Nausea and vomiting

Treatment for cystinuria includes:

• Drinking more water

• Eating less meat

• Reducing your salt intake

• Limiting your intake of potato chips, French fries, sandwich meats, and ready meals

In this type of stone, cystine leaks from the kidneys into the urine _ cystine acid is formed naturally in the body.

What are struvite stones?

This type of stone is less common, and it occurs most often(9) in people with chronic or untreated urinary tract infections.

Struvite stones are caused by a kidney infection. Symptoms of a kidney infection usually appear within two days of infection.

Symptoms may vary depending on age. Common symptoms include:

• Pain in the abdomen, back, or side

• Frequent urination

• Burning during urination

• Blood in the urine

• Foul-smelling urine

• Fever

Treating the underlying infection can prevent the development of struvite stones.

These stones can be large and cause obstruction in the urinary tract, so seeing a doctor will determine the type and size of the stones.

What causes kidney stones? 

Various factors can increase your risk of developing kidney stones.

In the United States, white people are more likely to develop kidney stones than black people.

Kidney stones most often occur(10) in people between the ages of 20 and 50.

Gender(11) also plays a role in stone formation, with men developing kidney stones more often than women.

Excess calcium and oxalate, lack of fluids, frequent urinary tract infections, and genetics are among the risk factors for stone formation.

Other risk factors include(12):

• Certain digestive conditions that increase calcium absorption, such as inflammatory bowel disease and chronic diarrhea

• Dehydration and poor fluid intake

• Being overweight or obese

• Excessive consumption of energy drinks, smoking and alcohol

• Eating a diet high in protein, sodium, and glucose

• Recent gastrointestinal surgery 

• Menopause

• Hyperparathyroidism

• Adults with osteoporosis

• Sedentary lifestyle

• Diabetes

• High blood pressure

• Pregnancy

• Taking medications(13), such as diuretics containing triamterene, anti-seizure medications, and antacids that contain calcium. Allopurinol (Zyloprim) and topiramate (Topamax)

People should see their doctor if they have concerns about any medications they are taking or any medical conditions that may be a risk factor, and they have symptoms of kidney stones.

What are the signs and symptoms of kidney stones? 

Kidney stones may not always cause symptoms. A person may pass very small stones in their urine without experiencing symptoms.

But large kidney stones can cause severe pain. Symptoms of kidney stones may not appear until the stone begins to move down the ureter.

This severe pain is called renal colic. The pain of renal colic comes and goes but can be severe.

Other symptoms of kidney stones can include(14):

• Blood in the urine

• Nausea and vomiting

• Frequent need to urinate small amounts

• Fever and chills if there is an infection

• Foul-smelling urine

• Pain in the groin or side of the abdomen or both

• Urinary tract infection (UTI)

If the kidney stones are large and block the flow of urine properly, a kidney infection may result. Symptoms include(15):

• Fever and chills due to infection

• Weakness and fatigue

• Cloudy urine with a foul odor

• Diarrhea

If a person has any of these symptoms, they should contact their doctor to prevent the condition from progressing.

Diagnosis of urinary stones

There are many tests that show whether urinary stones are present or not. The diagnosis begins as follows:

• A physical examination determines that the kidneys are the source of the pain

• A CT scan or ultrasound scan(16) reveals whether or not stones are present

• A urinalysis reveals blood in the urine or signs of bacterial or other infections

• Blood tests help identify complications

The most important diagnostic method that doctors need is imaging. Imaging can help determine:

• Whether a stone is present

• The size and location of the kidney stones

• The condition of the urinary tract

• The presence of blockages in the urinary tract

• Whether there are any complications from the stones

Ultrasound may be better than CT scans because they do not require the use of radiation, especially during pregnancy.

Treatment of kidney stones

Treatment aims to remove the stones from the urinary tract and manage symptoms until the end of the pain. 

Treatment will focus on medications and painkillers for small stones. Large stones may need to be broken up. Treatment includes(17):

• Painkillers

• Drinking large amounts of fluids by mouth, especially water

• Medications that help dissolve the stones and speed up their passage

Large stones may need other types of intervention, such as(18):

• Shock wave lithotripsy (SWL) which is ultrasound

• Percutaneous nephrolithotomy (PCNL) by breaking them up with a laser

• By laser through a ureteroscope tube

Some complications, such as infection and urinary tract infection, may occur after removing a large kidney stone.

The specialist doctor who will perform the lithotripsy explains the possible complications in advance so that the person can recognize the signs if they occur.

How long does it take for a kidney stone to pass?

There is no specific time frame for passing a kidney stone.

There are two main factors that determine how quickly a stone passes: size and location.

The size of a kidney stone plays a role in how quickly it passes through a person’s body.

The smaller the stone, the faster and less painful it will pass.

Here are different sizes(19) of kidney stones and the approximate time it takes to pass from the body:

• About 80% of kidney stones that are smaller than 4 mm pass on their own in about 31 days

• About 60% of kidney stones that are between 4 and 6 mm pass on their own in about 45 days

• Kidney stones larger than 6 mm may pass on their own in about 12 months, but often require fragmentation or surgery

The location of the kidney stone also plays a role in whether or not a person is able to pass it naturally.

One study(20) showed that 48% of stones that form in the upper part of the ureter near the kidney pass without surgery or fragmentation. As for stones that form in the lower part near the bladder, 79% of stones pass easily.

What are the stages of kidney stone passage?

 The process of kidney stones passing takes several days, weeks, or months to pass through a person's body, as they go through several stages during the period. 

The stages start after the kidney stone is formed, until it reaches the urethra and then exits. 

The following are the stages(21) that occur when a kidney stone passes:

• Stage 1: After the kidney stone forms, you may experience cramps as your kidneys try to push the stone out. This can cause severe pain in your back or side in waves

• Stage 2: During this stage, the stone enters the ureter, which is the tube that connects the kidney to the bladder. Depending on the size of the stone, this stage can also cause pain

• Stage 3: After the stone reaches the bladder, most of the pain subsides. However, you may feel increased pressure in the bladder and the need to urinate frequently. In some cases, the stone may temporarily remain at the opening of the urethra, which may block the flow of urine

• Stage 4: The final stage begins after the stone reaches the urethra.  During this stage, you need to push hard to pass the kidney stone with urine through the urethra

The doctor determines through appropriate imaging the stage where the kidney stone is located.

Medication and pain management

Drinking six to eight glasses of water a day increases urine flow.

People with dehydration or severe nausea and vomiting may need intravenous fluids.

Studies(22) have shown that patients taking statins have a lower risk of developing urinary tract stones, due to the close association(23) between high blood lipids and kidney stones.

Pain relief may require narcotic medications. Infection may require antibiotic treatment. Other medications include(24):

• Thiazide diuretics to prevent calcium stones

• Allopurinol (Zyloprim) to treat uric acid stones

• Phosphorus solutions to prevent calcium stones

• Sodium bicarbonate or sodium citrate to reduce urine acidity

• Acetaminophen (Tylenol) for pain relief

• Ibuprofen (Advil) for pain relief

Passing a kidney stone can cause pain and discomfort, so your doctor may recommend an over-the-counter pain reliever, such as acetaminophen or ibuprofen, to help reduce symptoms.

For severe pain, your doctor may also prescribe(25) a narcotic or inject you with an anti-inflammatory medication, such as ketorolac (Toradol).

Other natural remedies may also provide short-term relief from symptoms, including taking a hot bath or applying a heating pad to the affected area.

How to protect your body from kidney stones?

Prevention is better than feeling pain, taking medications, painkillers, and exposure to radiation. Include:

• Drinking adequate fluids is a key preventive measure, as it is recommended to drink enough fluids to excrete at least 2.5 liters(26) of urine per day. Increasing the amount of urine helps cleanse the kidneys

• If stones are associated with low citrate levels, citrate juices such lemon may help prevent stone formation

• Eating foods rich in calcium along with reducing sodium may preven(27)t the formation of calcium oxalate crystals

• Eating foods rich in magnesium prevents(28) the crystallization of calcium oxalate in the body, and magnesium also prevents the absorption of food oxalate from the intestinal cavity and stomach

• Eating foods rich in oxalates in moderation such as okra, sesame and spinach

• Eating foods rich in potassium helps prevent(29) kidney stones

• Foods rich in potassium include moringa, bananas, avocado, watermelon, almonds, orange juice, blueberries and papaya

• Eating healthy foods rich in anti-inflammatory, omega-3 and vitamin C supports kidney health and reduces the occurrence of stones

• Reducing your intake of salt and animal proteins can also reduce your risk of kidney stones

• Recent studies(30) suggest that increasing physical activity, such as walking or running, may reduce the risk of kidney stones

If you have kidney stones or are at risk for kidney stones, talk to your doctor and discuss the best prevention methods.

What foods can cause kidney stones?

In addition to drinking more water, making changes to your diet can also help prevent kidney stones.

Some foods you may need to limit or avoid(31):

• Processed meats

• Fast food 

• Frozen meals 

• Salty meals 

• Beef and pork 

• Chicken 

• Fish 

• Eggs 

• Milk 

• Cheese 

• Yogurt 

Animal proteins such as meat, poultry, seafood, and dairy products can increase uric acid levels in the urine and thus increase the risk of kidney stones for people with and at risk of developing kidney stones.

Oxalates are found in many common foods, such as:

• Nuts

• Beets

• Tahini

• Chard

• Rhubarb

However, people should not completely avoid foods containing oxalates, calcium, and protein, which can have other nutritional benefits.

Summary

Not drinking enough fluids may be a major cause, but eating habits, obesity, and a sedentary work lifestyle can all contribute to kidney stones.

Anyone experiencing symptoms of kidney stones or a kidney infection should see a doctor as soon as possible to determine treatment and prevent complications.