article_snippet.sent: two large stones often remain symptomless while two large stones're in the kidney.
article_snippet.sent: Virtually all stones under 5 mm in diameter can be passed naturally, with only prescription-strength pain relief and medication that relaxes the ureter needed while this happens, says Mr Ajayi.
article_snippet.sent: But if a stone is bigger, you may need to have treatment.
article_snippet.sent: This works for stones up to about 10 mm in diameter, but not for bigger ones, or for stones that are very hard,' says Mr Ajayi.
article_snippet.sent: For bigger or harder stones, a ureteroscopy is performed.
article_snippet.sent: For very large stones (those over 15 mm), percutaneous nephrolithotomy (PCNL) is used.