What Are Struvite Stones?

Medically Reviewed by Minesh Khatri, MD on September 15, 2023
Written by WebMD Editorial Contributors
3 min read

Struvite stones, also known as infection stones, are kidney stones made of magnesium ammonium phosphate.

Struvite stones are often associated with urinary tract infections and other conditions. Read on to learn more about struvite stones, what causes them, how to treat them, and more.

Struvite stones are a common type of urinary or kidney stones that are made of magnesium ammonium phosphate (MgNHPO4·H2O). They make up around 10 percent of all kidney stones.

Struvite stones are also called infection stones because they are associated with urinary tract infections. 

If struvite stones aren’t removed in time, they can grow rapidly and cause a variety of health conditions.‌

Struvite stones are created when bacteria, such as Proteus or Klebsiella, enter your body and break down the urea in your urine into ammonia, eventually resulting in increased urine pH and creating struvite. ‌

These bacteria are more likely to infect women since women have shorter urethras, which makes entry easier.

If you have struvite kidney stones, you may have the following symptoms:

  • Urinary tract infection
  • Kidney injury, since struvite kidney stones can get very large and fill up your kidneys. The bacteria responsible for struvite stones can also infect other types of calcium kidney stones to produce mixed stones to create more injuries
  • Sharp, severe pain below your ribs, in your side and back
  • Burning sensation or pain when urinating
  • Pain that can spread to your groin and lower abdomen
  • Red, pink, or brown urine
  • Frequent urination
  • Urinating in small amounts at a time or more than usual
  • Chills and fever

Pain caused by a struvite stone may change in intensity or location as it moves through your urinary tract. If you’re experiencing any of the above symptoms, talk to your doctor to get a proper diagnosis. 

Your doctor may order the following tests to find out if you have struvite stones and what’s causing them:

  • Imaging tests. X-rays, computerized tomography (CT) scans, and ultrasounds can determine the size and location of potential kidney stones.
  • 24-hour urine collection tests. These can help determine if you’re producing too few stone-preventing substances or too many stone-forming minerals. Your doctor may ask you to do two urine collections over two days.
  • Blood tests. These can reveal if you have a high level of waste products such as uric acid that can turn into stones.
  • Analysis of passed stones. This test involves urinating through a filter to see if you pass any stones. Lab tests will then be done to analyze the composition of your kidney stones. 

‌Your doctor will use all of this information to discover why you have kidney stones and create a treatment plan to remove and prevent kidney stones.

Struvite stones should be treated as soon as possible. If they’re not treated in time, they can become very large and damage your kidney, leading to serious infections. Since struvite stones are caused by bacteria, doctors may use a mixture of antibiotics and surgery to remove the stones and kill the bacteria creating them.

Surgical methods include shock wave lithotripsy (SWL) or percutaneous nephrolithotomy or nephrolithotripsy.

SWL uses intense shock waves to break up struvite stones into smaller pieces, which will pass through your urinary tract and come out when you urinate. If you have many stones or very large stones, you may have to go through this procedure a couple of times.‌

Percutaneous nephrolithotomy or nephrolithotripsy is used when you have stones that are too large to be split by SWL. The surgeon will access your kidney through a small hole in your back and use a nephroscope (a small camera) and other small tools to remove the stones.‌

If the stones are removed through a tube, it’s called nephrolithotomy. If it’s broken up and then removed, it’s called nephrolithotripsy.

If there are a lot of mixed stones, your doctor will also make a plan to prevent new calcium stones from forming.

Doctors may prescribe the following to prevent struvite stones from forming:

  • Acetohydroxamic acid
  • Pyrophosphate
  • Trisodium citrate
  • Disodium EDTA

You can also try to change your diet to make your urinary tract more inhospitable to bacterial infections. Consult a registered kidney dietitian about how you can change your diet and if you need any medical treatment to prevent kidney stones from coming back.