Kidney stones can be quite painful if they are large in size and not treated. The size of the kidney stone that requires surgery varies depending on the source. Here are some general guidelines:

• Smaller stones: Stones that are 4mm or less in length and may pass on their own within a month. Among these, 60 percent of the stones will pass naturally.

• Stones between 4mm and 6mm: On average, take 45 days to exit the body on their own. Among these, 60 percent of the stones will pass naturally.

• Stones larger than 6mm: These are the kidney stone size for surgery. Surgical treatment is usually recommended for stones 0.5 centimeters in size and larger. Stones that are larger than 7 mm rarely pass without a surgical procedure.

• Kidney stones larger than 40 mm: These should be treated primarily by percutaneous nephrolithotomy (PNL) .

The procedures used today to remove stones are minimally invasive and highly effective. The size and location of the stone, as well as other complicating factors, will determine the best treatment option. Here are some examples:

• Ureteroscopy with laser lithotripsy (URS): May be used for stones up to 2 centimeters in size located anywhere in the ureter or kidney. A laser is used to break the stone into smaller pieces that can be removed or passed in the urine.

• Percutaneous nephrolithotomy (PCNL): The best option for larger kidney stones (i.e., those greater than 2 centimeters in size) or when there are other complicating anatomic factors. PCNL involves making a half-inch incision in the back through which the surgeon extracts stones using a nephroscope.

It is important to note that the goal in any kidney stone surgery is to treat all stones at once. However, some people with kidney stones require a staged treatment approach in which more than one surgery is needed to reduce or clear the stones.