The natural course of kidney stones without treatment must be balanced against the relatively limited risks of treatment that are now possible with non-surgical techniques. Kidney stones that are more than 1 cm. in size (about 1/2 an inch) within the kidney will rarely pass through the urinary system without complications. Therefore, treatment is recommended for kidney stones larger than 1 cm (and many smaller stones within the kidney.)

The kidney stone has passed into the ureter, the tube that connects the the kidney to the bladder, is the stone most likely to create symptoms. The ureter is a narrow tube that propels urine along toward the bladder with rhythmic contractions. When a stone gets into the ureter, it may stop at the edge of the pelvis or just outside of the bladder, two natural areas of narrowing within the ureter. If the stone blocks urine flow, pressure builds up in the ureter and subsequently the kidney, causing the classic rhythmic spasms of pain associated with kidney stones. Pain medication is required for these cases, and infection behind a stone must be aggressively managed. But what happens to the stone if it's not removed?

The chance of a ureteral stone passing is proportional to the width of the stone. For stones less than 3 mm in width, the chance of spontaneous stone passage is very high. Stones more than 8 mm. in width are only about 20% likely to pass spontaneously over one year. Unfortunately, stones may produce significant pain and symptoms during passage and additional treatment may be required, so earlier treatment is suggested for larger stones.

For anyone who has suffered the pain of a kidney stone passing through the ureter, the possibility of a second stone is not an enticing possibility. Unfortunately, 60% of patients who have a kidney stone will have another stone, emphasizing the importance of evaluating the possible causes of stone formation and prevention.