Table 1.

Distribution of the patients with respect to the stone type and the initial stone diameter

№	Type	Number of patients	Initial stone diameter (mm)	SE (SD) m (σ)
1.	Simple stones	446	18.2	0.4 (8.1)
2.	Complex stones	581	39.6	0.8 (20.4)
	Within the complex stones:
a.	Two or more stones (multiple stones)	384	34.5	0.8 (16.6)
b.	Staghorn stones and staghorn stones in combination with a single or multiple stones	197	49.4	1.7 (23.4)
Total:		1027	30.3	0.6 (19.4)

p<0.01 between all groups