Kidney stones are solid deposits of minerals that can form in the kidneys, also known as renal calculi. They can be made up of various types of crystals, with the most abundant crystal determining the type.

Depending on the size of the stone, it may exit your body by traveling through your urinary tract when you urinate. Less often, the stones are too large and need to be removed surgically. Kidney stones are frequently very painful and can result in a visit to an emergency room.

Risk factors of kidney stones include:

Read on to learn more about the different types of kidney stones.

There are four types of kidney stones:

  • calcium stones
  • uric acid stones
  • struvite stones (triple phosphate, or magnesium ammonium phosphate)
  • cystine stones

Calcium stones are the most common type, and they can be further divided into two subgroups based on the molecules they’re made from:

Different types of stones may form crystals of different shapes. Some types are more common than others. They might present at different ages, occur more frequently in men or in women, or have different rates of recurrence (the chances of having another kidney stone later).

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Illustration by Alyssa Kiefer.

If you have a kidney stone, you may want to know what type of stone it is. This is not something you can figure out on your own.

A doctor can find out more about your kidney stone by using different types of diagnostic tests. These may include imaging tests like an abdominal X-ray or CT scan (computed tomography), or lab tests like a urinalysis or blood test.

Imaging tests provide the doctor with visual information about the stone, such as its size, shape, and location. They might also be able to identify causes or complications, such as a urinary tract obstruction.

Lab tests like urinalysis or a blood test provide samples of the different types of molecules present in your urine or blood, respectively. Elevated levels of calcium, phosphorus, and other compounds can indicate which type of stone you have.

Once you’ve passed a stone or had it surgically removed, it will often be sent to a lab to be analyzed. This stone analysis can be used to determine whether you’re likely to have another stone.

Your doctor can help you determine what you might be able to do to prevent a recurrence.

Once a kidney stone has formed, the treatment will be the same regardless of what type of stone it is. It will, however, be highly dependent on the size of the stone.

The tube that moves urine from your kidney to your bladder is called the ureter. The average ureter has an internal diameter of just 3mm to 4mm.

For stones that are small enough to pass through your ureter, the least invasive treatment is to pass them naturally. A healthcare professional may recommend drinking lots of water. You might also take medication to help manage pain or reduce urine acidity. This could take from 4 to 6 weeks.

Larger stones will need more immediate treatments.

Lithotripsy is an outpatient procedure used to break kidney stones into smaller pieces so they can pass on their own.

Cystoscopy or ureteroscopy can be used to remove or break up kidney stones. During these procedures, a doctor inserts a special instrument through your urethra to reach the stone.

For very large stones, you may need to have them surgically removed with a procedure called a percutaneous nephrolithotomy.

Different types of kidney stones form for different reasons. Preventative measures for different types of stones have a lot of overlap, but can be slightly different.

The most important thing you can do to prevent most kidney stones is to drink enough water every day. This may be a different amount depending on your age and gender.

Following a DASH diet can generally lower your risk of kidney stones. Depending on what type of stone you have, you may want to specifically reduce the amount of sodium, animal protein, or oxalate in your diet. A dietician can help you put together a meal plan to meet your needs.

While most kidney stones are calcium stones, it’s not always a good idea to reduce your calcium intake. If your dietary calcium is too low you can actually increase your chances of forming a kidney stone. Check with your doctor to find out if your calcium intake is moderate.

Cystine stones are caused by a genetic disorder and may need to be treated with medications that raise the pH level of your urine. But drinking enough water and eating a healthy diet generally applies to these stones as well.

Kidney stones come in four main types: calcium, uric acid, struvite, and cystine.

Treatment methods are very similar for all types of kidney stones. The size of the stone is often the most important factor for determining treatment.

Different types of stones can have different causes, such as diet, infection, or inherited conditions. Knowing which type of stone you have can help determine the best way to prevent future stones.