Why size matters more than anything else

When patients ask,
“Can I pass this stone naturally?”

The real question is:
How big is it?

Stone size is the strongest predictor of whether your body can pass it without intervention.

Stone Size Guide (Easy to Understand)

Stones smaller than 4–5 mm

• High chance of natural passage

• Often pass within days to weeks

• May still cause significant pain

Stones 5–7 mm

• Moderate chance of passage

• May require medication to assist passage

• Often cause repeated pain episodes

Stones 7–10 mm

• Low chance of natural passage

• Frequently require treatment

• Higher risk of obstruction

Stones larger than 10 mm

• Very unlikely to pass on their own

• Usually require active treatment

But size is not the only factor

Other factors that influence passage:

• Stone location (kidney vs ureter)

• Ureter width

• Previous stone history

• Degree of obstruction

• Infection risk

A 6 mm stone in the lower ureter may pass.
A 6 mm stone high in the ureter may not.

When waiting is reasonable

Observation may be considered when:

• Stone is small

• Pain is manageable

• No infection

• Kidney function is normal

Monitoring with follow-up imaging is important.

When not to wait

You should not delay treatment if:

• Fever is present

• Pain is uncontrolled

• Kidney function is affected

• Stone is too large

• Repeated ER visits occur

Delaying treatment in these situations can risk kidney damage.

Where does SWL fit in?

Shockwave Lithotripsy (SWL) is commonly used for:

• Stones 5–20 mm

• Stones visible on imaging

• Suitable anatomical positioning

It bridges the gap between waiting and invasive procedures.

Use our Stone Location Tool to understand your stone better
Estimate your Stone Recurrence Risk
Learn how SWL works in detail in our treatment guide