There was no significant difference among the groups in terms of mean age (A, 23.21 ± 4.11 years; B, 28.53 ± 9.14 years; C, 26.19 ± 8.86 years; D, 25.19 ± 11.81 years); sex ratio (female/male, A, 13/12; B, 11/10; C, 16/17; D, 17/14); body mass index (A,25.53 ± 1.82 kg/m2; B, 23.18 ± 3.61 kg/m2; C, 26.55 ± 3.34 kg/m2; D, 25.08 ± 3.86 kg/m2) ;total stone volume (A, 3.42 ± 0.16 cm3; B, 3.96 ± 0.21 cm3; C, 4.11 ± 0.51 cm3; D, 3.89 ± 0.41 cm3); stone volume in the renal pelvis; or stone volume in the upper, middle, or lower renal calyx. There was one 13 year-old patient in Group D. The preoperative clinical and demographic profiles of the patients are shown in Table 1.

Successful surgery was considered successful if pyeloplasty was successful and the patient was stone free. The surgery success rates in Groups A, B, C and D were 68.00, 85.71, 78.79 and 94.29%, respectively. The difference in stone clearance rates among the four groups was significant. The stone clearance rate and pyeloplasty success rate were also used to assess treatment efficacy. The stone clearance rates in Groups A, B, C and D were 68.00, 85.71, 78.79 and 94.29%, respectively. The difference in stone clearance rates among the four groups was significant. The pyeloplasty success rates in Groups A, B, C and D were 92.00, 95.24, 93.94, and 94.29%, respectively. The pyeloplasty success rates were not significantly different among the four groups. The clinical profiles of the patients are shown in Table 2.

The operation time was ranked fist for Group B (189.41 ± 25.62 min), second for Group C (153.75 ± 26.13 min), third for Group D (138.85 ± 26.13 min) and fourth for group A (189.41 ± 25.62 min). The differences among the four groups were significant.

The amount of bleeding was 52.31 ± 5.81 ml in Group A, 89.84 ± 15.6 ml in Group B, 23.45 ± 13.33 ml in Group C and 25.12 ± 12.87 ml in Group D. Compared to that in Group D, the amount of bleeding was not significantly different in Group C but was significantly greater in Groups A and B. Compared with that in Group A, the amount of bleeding in Group B was significantly greater.

The operation-related complications mainly included perirenal infection, urinary extravasation, and acute renal injury. In Group A, three patients suffered operation-related complications (3/25, 12.00%), two patients suffered both perirenal infection and urinary extravasation and one patient suffered a perirenal infection, urinary extravasation and acute renal injury at the same time. In Group B, four patients suffered operation-related complications (4/21, 19.05%), one patient suffered both a perirenal infection and urinary extravasation and three patients suffered a perirenal infection, urinary extravasation and acute renal injury at the same time. In Group C, three patients suffered operation-related complications (3/33, 9.09%), two patients suffered both perirenal infection and urinary extravasation and one patient suffered an acute renal injury. In Group D, two patients suffered operation-related complications (2/31, 6.45%), one suffered both a perirenal infection and urinary extravasation, and one suffered acute renal injury. The order from the highest to lowest operation-related complication occurrence rate was Group B, Group A, Group C and Group D. The differences among the groups were significant.

Postoperative pain was evaluated 1 week after surgery using the VAS. The VAS score was 6.61 ± 2.19 in Group A, 4.93 ± 1.85 in Group B, 2.92 ± 1.93 in Group C and 3.01 ± 1.63 in Group D. Compared with that in group D, the VAS score was not significantly different in Group C but was significantly higher in Groups A and B. Compared with that in group B, the score in Group A was significantly higher.

The LOS was 14.09 ± 3.67 days in Group A, 16.13 ± 4.23 days in Group B, 11.89 ± 3.91 days in Group C, and 10.99 ± 4.67 days in Group D. Compared with that in Group D, the LOS was not significantly different in Group C but was significantly longer in Groups A and B. Compared with that in group B, the LOS in Group A significantly longer.

The hospitalization costs were $2669.84 ± 342.89 in Group A, $3811.20 ± 433.82 in Group B, $3289.56 ± 564.23 in Group C and $4156.14 ± 459.58 in Group D. The difference in operation time among the four groups was significant.

The follow-up durations were not significantly different among the four groups. The clinical profiles of the patients are shown in Table 3.