Stones usually first develop in the kidneys. (For more information on the process of stone development, see: How do kidney stones form?) A kidney stone usually first causes symptoms when it tries to move down the ureter and out of the urinary system. As it makes its way down the ureter, it can cause blockage, which leads to the development of increased pressure in the kidney above. This pressure leads to the pain associated with passing a stone.
As a stone moves down the ureter, it tends to become lodged in three locations of natural narrowing: the ureteropelvic junction, the crossing of the ureter over the iliac vessels, and at the entrance of the ureter into the bladder. Depending on where a stone is located along this path, the pain associated with it can vary. Stone pain usually starts high up near the kidney then migrates towards the abdomen and eventually down towards the groin as the stone moves further down the ureter. As a stone is almost ready to come out, patients may feel the urge to urinate.
What about kidney stones that aren’t passing?
Most doctors feel that kidney stones only cause pain if they are blocking the ureter and trying to pass down towards the bladder. Stones that are not obstructing, such as those located in the kidney’s calyxes, are generally thought to be non-painful. This explains why some patients can have extremely large stones filling up their entire kidney with no or minimal pain.
However, it does appear that some non-obstructing kidney stones can cause pain because of either blockage of small tubular structures in the kidney itself (the collecting tubules) or for other unclear reasons. Supporting this view is a recent medical journal article suggesting that the treatment of small non-obstructing “papillary” stones may provide pain relief. (Gdor et al, Multi-institutional assessment of ureteroscopic laser papillotomy for chronic pain associated with papillary calcifications, J Urol 2011) Additionally, testimonials from many kidney stone patients (including a urologist with a personal history of kidney stones) suggest that some non-obstructing stones can cause pain.