Appropriate kidney stone size for ureteroscopic lithotripsy: When to switch to a percutaneous approach

Table 1 Natural history of asymptomatic kidney stones

Ref.	Study type	No. of patients	Follow-up	Disease progression (stone growth)	Symptomatic episode	Need for intervention
Glowacki et al[1]	Retrospective	107	31.6 mo	NA	31.8%	16.8%
Hübner et al[3]	Retrospective	80	7.4 yr	45%	68%	83%
Keeley et al[5]	Randomized prospective	200	2.2 yr	NA	21%	10%
Burgher et al[2]	Retrospective	300	3.26 yr	77%	NA	26%
Inci et al[4]	Retrospective	24	52.3 mo	33.3%	41.7%	11%

NA: Not available.