In recent years, the super mini-PCNL (SMP) technique has developed rapidly and matured gradually. However, the operation time may be prolonged when manage the large burden renal calculi with 14 F tract. On the basis of SMP, the suction sheath was increased to 18 F, in the aim to improve the lithotripsy efficiency and keep a low renal pelvic pressure, which was called enhanced-SMP (eSMP). In the present study, eSMP and mini-PCNL was compared to analyze the intra-operative renal pelvic pressure and stone removal efficiency when managed the 2-5 cm renal calculi, and to verify the safety and efficiency of eSMP technique.

From January 2017 to December 2019, 100 patients with 2-5 cm renal calculi in our hospital were randomly divided into eSMP group and mPCNL group. 18 Fpercutaneous tract was established, suction sheath with 11 F mini nephroscope and peel-away sheath with 8/9.8 F ureteroscope was used in eSMP and mPCNL, respectively. Ho:YAG laser and pneumatic lithotriptor was used for lithotripsy. During the operation, renal pelvic pressure was measured, operation time, lithotripsy time, removed stone volume and complications were recorded and analyzed statistically.

There was no significant difference in the stone volume removed between mPCNL group and eSMP group, but the lithotripsy time in mPCNL was significantly longer than eSMP group [(50.1±19.6) min vs (35.3±14.3)min, t=4.314, P<0.001], thus the stone removal effectiveness was higher in eSMP group [(13.66±1.17) mm³/h vs (9.78±1.23) mm³/h, t=16.150, P<0.001], and the total operation time in mPCNL group was longer than eSMP group [(67.3±19.5) min vs (52.1±14.4) min, t=4.429, P<0.001]. The intra-operative renal pelvic pressure in mPCNL group was higher than eSMP group [(17.88±3.28) mmHg vs (12.01±2.45) mmHg, t=10.140, P<0.001], and also the accumulated time of renal pelvic pressure >30 mmHg in mPCNL group was longer than eSMP group [(23.2±16.6) s vs (3.8±4.3) s, t=8.012, P<0.001]. The postoperative decreased hemoglobin in mPCNL group was more than eSMP group [(17.1±6.8) g/L vs (14.0±7.5) g/L, t=2.182, P=0.032]. There was no significant difference in the postoperative fever rate and stone clearance rate, while the hospital stay in mPCNL group was longer than eSMP group [(2.98±0.87) d vs (2.60±0.78) d, t=2.298, P<0.001].

Enhanced SMP (eSMP) was safe and effective in the management of 2-5 cm renal calculi. On the basis of irrigation-suction sheath, eSMP can keep a lower renal pelvic pressure and higher lithotripsy efficiency when compared to traditional mPCNL.