How Many mm Kidney Stones Pass Naturally and When Is Surgery Needed? Expert Explains

Kidney stones are a common health problem caused by the buildup of salts and minerals in the urine. Over time, these deposits harden and form stone-like structures. While some kidney stones are small and pass out naturally through urine, others can grow large and require medical procedures or surgery.

Why Do Kidney Stones Form?

Kidney stones usually develop due to poor dietary habits, dehydration, and certain medical conditions. Major causes include:

• High salt and protein intake.

• Low water consumption.

• Family history of kidney stones.

• Obesity, diabetes, high blood pressure, or gout.

Men are more prone to kidney stones than women.

Symptoms of Kidney Stones

Kidney stones may not cause symptoms when small, but as they grow or move into the urinary tract, they can trigger painful signs such as:

• Severe pain while urinating.

• Burning sensation in urine.

• Blood in urine.

• Frequent urge to urinate.

• Sudden, sharp abdominal or back pain (colic pain) when a stone blocks the urinary tract.

If left untreated, kidney stones can damage the kidneys, cause infections, and lead to serious complications.

How Many mm Kidney Stones Pass Naturally?

According to Professor Dr. Himanshu Verma, HOD of Nephrology at Safdarjung Hospital, the possibility of passing kidney stones naturally depends mainly on their size:

• Up to 4 mm: These usually pass out naturally with urine without much medical help.

• 5 to 7 mm: These may pass on their own, but it can take longer and may cause more pain.

• 8 mm or larger: Stones above this size rarely pass naturally and often require medical procedures.

When Does Surgery Become Necessary?

• 10 mm or larger stones generally block the urinary tract, causing severe pain and urinary difficulty.

• In such cases, doctors may recommend treatments like:

  • Lithotripsy (ESWL): Using shock waves to break stones into smaller pieces that pass through urine.

  • Ureteroscopy (URS): A thin scope is inserted through the urethra to remove or break the stone.

  • Open surgery or PCNL (Percutaneous Nephrolithotomy): Required for very large stones that cannot be treated by other methods.

The choice of treatment depends on the stone’s size, location, and the patient’s overall health condition.

Precautions to Prevent Kidney Stones

Doctors suggest that prevention is better than cure. Here are some simple lifestyle tips to reduce the risk of kidney stone formation:

• Drink plenty of water throughout the day to keep urine diluted.

• Limit salt and processed foods, as high sodium increases stone risk.

• Include citrus fruits like lemon, orange, and grapefruit, which help prevent stone formation.

• Avoid unnecessary supplements (especially calcium or vitamin D) unless prescribed by a doctor.

• Seek medical attention immediately if you experience burning, pain, or blood in urine.

Final Thoughts

Kidney stones up to 4 mm usually pass naturally, while stones above 8 mm are unlikely to come out on their own and often require medical intervention. Larger stones, especially 10 mm or more, can cause severe pain and urinary blockage, making surgical treatment necessary.

Taking preventive steps—such as staying hydrated, eating a balanced diet, and monitoring symptoms—can help you avoid complications and keep your kidneys healthy.