Last Updated on November 25, 2025 by

Knowing the size of a kidney stone you can pass on your own is key. Stones 4 mm or smaller can usually leave your body naturally in 90% of cases.

Most people can pass stones up to 4“5 mm in size without help. But what if the stone is bigger? New studies show when medical help is needed.

We’ll look at the latest on how often stones pass on their own by size. We’ll also talk about what affects kidney stones. This info helps both patients and doctors choose the right treatment.

Key Takeaways

• The size of a kidney stone that can be passed naturally is typically up to 4“5 mm.
• Stones 4 mm and smaller are expelled naturally in about 90% of cases.
• Larger stones often require medical intervention.
• Understanding the factors that influence stone passage is vital for treatment.
• Recent research provides insights into the tipping point for medical intervention.

Understanding Kidney Stones and Their Formation

It’s important to know about kidney stones, how they form, and the types that exist. Kidney stones are hard deposits made of minerals and salts. They form inside the kidneys and are influenced by many factors.

What are kidney stones, and how do they form?

Kidney stones form when there’s an imbalance in substances like calcium, oxalate, and uric acid in the urine. This imbalance causes these substances to crystallize and form stones. Dehydration, diet, and certain medical conditions can raise your risk.

The pH level of the urine also plays a role. For example, uric acid stones are more likely in acidic urine. Knowing this helps in preventing and managing kidney stones.

Common types of kidney stones

There are several types of kidney stones, each with its own causes and risk factors. The most common types include:

• Calcium stones: These are the most common type, often caused by excess calcium in the urine.
• Uric acid stones: These form when there is too much uric acid in the urine, often associated with diet and certain medical conditions.
• Struvite stones: These are typically associated with urinary tract infections (UTIs) and can grow quickly.
• Cystine stones: These are rare and usually occur in people with a genetic disorder that causes cystine to leak into the urine.

How kidney stone sizes are measured

The size of a kidney stone is important for treatment. Kidney stone sizes are measured in millimeters (mm). The size determines if a stone can pass naturally or if medical help is needed.

Knowing the size and type of kidney stone helps doctors choose the best treatment. We focus on high-quality, ethical, and advanced care for kidney stone management. We ensure patients get the support and guidance they need during treatment.

The Maximum Size of Kidney Stones That Pass Naturally

We look at how likely it is for kidney stones to pass on their own based on size.

4mm and smaller: High chances of natural passage

Kidney stones under 4mm often pass naturally. Research shows 80% to 90% of these small stones can leave the body without surgery. This is because the body can easily flush out smaller stones.

5-6mm: The borderline cases

Kidney stones between 5-6mm have lower chances of passing naturally. These are borderline cases. About 50% of stones in this range might pass on their own, but the risk of problems grows.

Statistical success rates for different-sized stones

Knowing these success rates is key for both patients and doctors to decide on the best treatment for kidney stones.

When Kidney Stones Require Medical Intervention

Some kidney stones can pass on their own, but others need medical help to avoid problems. The choice to see a doctor depends on the stone’s size and symptoms.

6-7mm Stones: Why Natural Passage Becomes Unlikely

Stones larger than 6mm rarely pass on their own. At this point, medical help is often needed to prevent long-term pain and other issues.

Stones this size can get stuck in the urinary tract. This can cause a lot of pain, infection, or even damage to the kidneys. If you have a stone this size, it’s best to get a medical check-up.

Stones Larger Than 10mm: Why Surgery is Almost Always Necessary

Surgery is often the best option for these stones because of the high risk of serious problems like pain, infection, and kidney damage.

• Severe pain that can’t be controlled with medicine
• Infection or signs of urinary tract blockage
• Kidney damage or risk of kidney failure

Complications of Untreated Large Kidney Stones

These include chronic kidney disease, recurring infections, and severe pain. It’s important to know that untreated kidney stones can be dangerous and may cause long-term health issues.

Some complications of untreated large kidney stones are:

1. Kidney damage or loss of kidney function
2. Urinary tract infections can spread to other parts of the body
3. Blockage of the urinary tract, leading to severe pain and potentially life-threatening complications

Treatment Options for Different-Sized Kidney Stones

Kidney stone treatment changes based on the stone’s size. It can range from simple care to surgery.

Conservative Management Approaches

For small stones, 4mm or less, conservative management is best. This means watching the stone with tests and using pain medicine. Drinking more water helps pass the stone. The National Institute of Diabetes and Digestive and Kidney Diseases says drinking water is key.

Minimally Invasive Procedures

For slightly bigger stones (5-6mm) or if symptoms are bad, minimally invasive procedures are suggested. Shockwave lithotripsy breaks the stone into small pieces. Ureteroscopic lithotripsy uses a small scope and a laser to break the stone.

Advanced Surgical Interventions

For big stones or severe symptoms, advanced surgical interventions are needed. Percutaneous Nephrolithotomy (PCNL) is great for big stones. Sometimes, open or laparoscopic surgery is needed. Our urologists at Liv Hospital use the latest tech for the best results.

Conclusion: Prevention and Management of Kidney Stones

Knowing how to prevent kidney stones is key. If you keep getting kidney stones, see a doctor right away.

At Liv Hospital, we focus on preventing and managing kidney stones. We offer top-notch healthcare and support for international patients.

FAQ

References

1. National Institute of Diabetes and Digestive and Kidney Diseases. (2022). Kidney stones in adults. Retrieved from https://www.niddk.nih.gov/health-information/urologic-diseases/kidney-stones/adults
2. Deters, L. A., & Monga, M. (2025). Urolithiasis. In StatPearls. StatPearls Publishing. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK560887/