Small kidney stones can pass out of the body in urine without a procedure, often over a few weeks. Larger stones, or stones that get stuck and block urine flow, may need medical treatment. Whether a stone passes depends on its size and location. Because a blockage or infection can be serious, medical assessment helps determine whether waiting is safe and what follow-up is needed.
How Can a Kidney Stone Pass on Its Own?
Kidney stones are hard deposits that form when certain minerals and other substances in urine collect and form crystals. A stone can remain in the kidney, move into the ureter (the narrow tube that carries urine from the kidney to the bladder), or travel farther through the urinary tract.
When a stone moves through the urinary tract and leaves the body during urination, it is said to have passed naturally. Very small stones may pass without causing noticeable symptoms. Others can cause pain as they move through the ureter. Passing a stone does not require surgery in every case, but a stone that cannot move through the urinary tract may need medical treatment.
Which Kidney Stones Are Most Likely to Pass Naturally?
The size and location of a kidney stone are important factors in whether it can pass without a procedure. According to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), small stones may pass through the urinary tract on their own, while larger stones are more likely to become stuck and block the flow of urine.
Smaller stones generally have a better chance of passing than larger ones. However, size alone does not determine the outcome. A stone's location and whether it obstructs urine flow also matter. A healthcare professional may use imaging tests to assess these factors and decide whether monitoring, medication, or a procedure is appropriate.
There is no single size that guarantees a stone will pass or establishes that a procedure is always necessary. The decision depends on the findings, symptoms, and risk of complications.
How Long Does It Take for a Kidney Stone to Pass?
A kidney stone may take several weeks to pass naturally. The exact time varies, and not every stone passes without treatment. The NHS guidance on kidney stones notes that stones can take a few weeks to pass even when they are managed at home with medication.
During this period, symptoms may come and go. Pain can become less intense or disappear temporarily, but this does not always mean the stone has left the urinary tract. A stone may still be present even when discomfort improves.
If a healthcare professional recommends waiting for a stone to pass, follow the agreed monitoring plan. Seek reassessment if pain continues, symptoms worsen, or the expected passage does not occur within the advised timeframe. Follow-up is important because a stone that remains stuck can interfere with urine flow.
What Can You Do While Waiting for a Kidney Stone to Pass?
When a stone is suitable for natural passage, treatment may focus on controlling symptoms and helping the stone move through the urinary tract. According to the NIDDK's guidance on kidney stone treatment, a healthcare professional may recommend adequate fluid intake, pain medicine, or other medication to help with passage.
The appropriate plan depends on the stone and your overall health. Practical steps may include the following:
- Follow fluid advice: Drink fluids as recommended by your healthcare professional. The appropriate amount may depend on your health and any restrictions you have been given.
- Use medication as directed: Pain-relieving medicines may help manage discomfort. In some cases, prescription medication can help a stone pass. Use medicines according to your clinician's instructions.
- Collect the stone if advised: Your healthcare professional may ask you to strain your urine or use a collection container so the stone can be examined. Testing the stone can help guide future prevention.
- Attend follow-up appointments: Your clinician may recommend further tests to check whether the stone has passed and whether urine flow has returned to normal.
Home care is not suitable for every stone. A stone that causes obstruction, infection, uncontrolled pain, or other complications may require more immediate treatment rather than continued waiting.
When Does a Kidney Stone Need Medical Treatment?
A kidney stone may need treatment if it is too large to pass, becomes stuck, blocks urine flow, or causes pain that cannot be adequately controlled. Treatment may also be needed when a stone is associated with infection or a risk of kidney damage.
Depending on the stone's size and location, a healthcare professional may recommend medication and monitoring or a procedure to remove or break up the stone. Common procedures include shock wave lithotripsy, which uses shock waves to break a stone into smaller pieces, and ureteroscopy, in which a thin instrument is passed through the urinary tract to locate and treat the stone. Some larger stones require a different removal procedure.
Choosing a procedure does not automatically mean that the condition is unusually serious. It may simply mean that the stone is unlikely to pass safely or promptly on its own. The decision should be based on clinical assessment rather than symptoms alone.
Which Symptoms Need Urgent Medical Attention?
Kidney stones can cause pain in the back, side, lower abdomen, or groin. Some people also experience nausea, vomiting, blood in the urine, or discomfort when urinating. These symptoms can have different causes, so they should be assessed in context rather than used alone to determine whether a stone is present.
The NIDDK guidance on kidney stone symptoms advises seeking medical care for concerning symptoms, including severe pain, blood in the urine, difficulty passing urine, fever, or chills.
Seek urgent medical care if you experience any of the following:
- Severe or persistent pain in the back, side, abdomen, or groin.
- Fever or chills, especially when urinary symptoms are also present.
- An inability to urinate or passing only a very small amount of urine.
- Repeated vomiting or difficulty keeping fluids down.
- Blood in the urine, particularly when accompanied by pain or other new symptoms.
Fever or chills with a possible urinary blockage can indicate an infection that needs prompt treatment. Do not wait for a stone to pass on its own when these warning signs occur. Severe or worsening symptoms should not be managed by continuing home observation without medical advice.
How Can You Tell Whether a Kidney Stone Has Passed?
You may notice a small stone in your urine, and symptoms may improve after it leaves the urinary tract. However, the disappearance of pain is not reliable proof that the stone has passed. According to the MedlinePlus Medical Encyclopedia, a previously identified blockage may need confirmation through stone collection or follow-up imaging, even when pain has stopped.
Your healthcare professional may recommend an imaging test, such as an ultrasound or CT scan, depending on your circumstances. Urine and blood tests may also help assess the condition and identify related problems. The need for follow-up depends on the stone, whether a blockage was present, and the treatment plan.
If you were told that a stone was blocking urine flow, do not assume that it has cleared simply because you feel better. Follow the recommended plan for confirming passage and checking that there is no remaining obstruction.
What Is the Main Takeaway About Kidney Stones Passing Naturally?
Many small kidney stones can leave the body without surgery, but some stones remain stuck and need medical treatment. The likelihood of natural passage depends largely on the stone's size and location, and passage may take several weeks. Medical assessment can help determine whether waiting is appropriate, while follow-up helps confirm that the stone has passed when necessary. Prompt attention to warning signs can reduce the risk of complications.