The kidneys are responsible for removing urea and excess minerals from the blood. The body usually excretes these products in the urine. In some cases, however, large amounts of these minerals can accumulate in the kidneys, forming crystal-like stones.

Kidney stones can form in one or both kidneys. From here, they may pass into the ureter, which is the tube that connects the kidney to the bladder.

Small kidney stones often travel without any issues and may not cause symptoms. Larger stones can lodge themselves in the ureter, causing pain. Without removal, they may cause complications such as infection and kidney damage.

There are several factors that can affect how quickly a kidney stone passes. This article provides more information on the time it takes to pass a kidney stone, ways to speed up the process, and treatment options.

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

Size

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Most kidney stones that are less than 4 mm will usually pass naturally.

The size of a kidney stone plays a role in how quickly it will pass through a person's body. In general, smaller stones pass faster and with less pain.

Below are the approximate timelines for passing kidney stones of different sizes:

  • Around 80% of kidney stones that are smaller than 4 millimeters (mm) will pass on their own in about 31 days.
  • Approximately 60% of kidney stones that are 4–6 mm will pass on their own in about 45 days.
  • Around 20% of kidney stones that are larger than 6 mm will pass on their own in about 12 months. However, when stones are this large, it is best to seek immediate surgical removal.

Location

The location of the kidney stone also plays a role in whether or not a person will be able to pass it naturally. Some stones form in the kidney itself, while others may form in the ureter.

Kidney stones that form in the upper part of the ureter are close to the kidney. Those that form in the lower part are close to the bladder.

According to research outlined in a 2014 review, 48% of stones that form close to the kidney pass without intervention. This number rises to 79% for stones that form close to the bladder.

The best way to help speed up the process of passing a kidney stone is to drink plenty of water. The excess fluid encourages urination, which helps move the stone along.

A person can also take steps to prevent new stones from forming and to stop existing ones from growing larger. These steps include:

  • limiting protein intake
  • reducing calcium intake
  • consuming less salt
  • eating more citrus fruits

Citrus fruits contain the chemical citrate, which helps prevent the formation of kidney stones.

Additionally, dietitians or doctors can suggest diet plans for kidney stone management.

Passing kidney stones can be uncomfortable and even painful. In some cases, taking over-the-counter medications such as ibuprofen may be enough to alleviate the pain.

If a person is experiencing particularly painful kidney stones, they should talk to their doctor, who may be able to prescribe stronger pain relief medications.

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A person should talk to their doctor if they experience persistent pain in the back or side.

Smaller kidney stones may pass on their own, causing minimal discomfort. However, large stones can be painful and increase the risk of health complications.

Pain is an indicator that a person should see a doctor. They can determine whether or not the stone requires additional treatment to help it pass.

People should also see a doctor if they experience the following symptoms:

These may be signs of a kidney infection, which requires prompt treatment to prevent more serious complications.

There are several nonsurgical treatments for kidney stones. These include:

  • Alpha-blockers: These drugs relax the ureter, alleviating painful spasms and helping the stone pass.
  • Calcium channel blockers: These drugs widen the ureter, helping the stone pass through.
  • Lithotripsy: This procedure uses sound waves to break the stone into smaller fragments that can pass more easily.

Surgery is rarely the first choice of treatment. However, kidney stones larger than 6 mm require immediate surgery. Stones this large can stick in the ureter, causing infections and kidney damage.

There are two main surgical options for kidney stone removal: ureteroscopy and percutaneous nephrolithotomy.

Ureteroscopy requires general anesthetic. During the procedure, the surgeon removes or breaks up the stone, using tiny instruments inserted through the urethra. The surgeon may then place a stent inside the urethra to hold it open. This allows any small stone fragments to pass more easily.

During percutaneous nephrolithotomy, the surgeon removes very large stones measuring 10 mm or more. It involves removing the stone directly from the kidney through a small incision in the back. The procedure requires general anesthetic and a 1–2 day hospital stay.

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A person may find pain medication helpful during their recovery.

The amount of time it takes to recover from a kidney stone depends on how it passes. If the stone passes naturally or with minimal drug intervention, the pain should subside very quickly.

If a person undergoes lithotripsy, which is an outpatient procedure, they should be able to go home the same day. Recovery time is usually minimal and partly depends on the type of anesthetic a practitioner uses.

If surgery is required, a person will typically be able to return to most normal activities within a day of the procedure. However, people who receive a stent should avoid high intensity activities until a health professional removes it. This usually occurs about a week after surgery.

During recovery, a person may take pain medications.

Kidney stones are often painful and can take several weeks to fully pass through the body's system. A person should see a doctor if their stones become particularly painful or if they experience other worrying symptoms.

There are several potential treatment options for kidney stones. Drug therapies focus on both alleviating pain and discomfort and allowing the stone to pass more easily.

However, kidney stones that are too large to pass naturally may require surgical removal. In most cases, a person can return to their normal activities within a day or two of surgery.