The present study is a prospective comparative study that was conducted on 80 patients who had radio-opaque renal stones 2–4 cm, they were randomized to undergo either mini-PCNL or standard-PCNL.

Characteristics of the patients included in the study showed no significant difference regarding mean age, gender, mean BMI and mean stone size. The endpoints of the study were: operative time, blood loss, Intraoperative and postoperative events, stone free rate, hospital stay, and postoperative pain. Operative time in mini-PCNL and standard-PCNL was calculated from the time of cystoscopy till securing the nephrostomy tube.

The mean operative time for mini-PCNL was (95 ± 17 minutes) which was longer than the operative time in standard-PCNL (72 ± 14.9 minutes), these results are similar to study by Qin et al [10]. Zhu et al compared mini- PCNL vs standard-PCNL. It was concluded that operative time was shorter in the standard-PCNL group [8]. In our series, and in other studies, the operative time cannot be considered as an absolute criteria of advantage of one technique over the other, although there are criteria in selection as stone size, but other criteria are variable from one case to the other, these element includes multiplicity, harness of the stone, location, and calyceal stone.

Hospital stays calculated from the day of surgery to the day of discharge was (2.05 ± 0.9) days for mini-PCNL patients, compared to (3.4 ± 1.1) days in standard-PCNL. Zhu et al in a Systematic review and meta-analysis showed a shorter hospitalization for mini- PCNL group [8]. The present study showed that hospital stay was shorter in mini-PCNL group compared to standard-PCNL, this finding imply a great advantage of the mini-PCNL for the patients and in reducing costs of the procedure.

Blood loss was assessed by comparing the pre and post-operative hemoglobin level in day one postoperative. Blood loss in terms of the mean change in Hb level in mini-PCNL group was (0.58 ± 0.64) gm/dl which was lower when compared to standard-PCNL group (1.64 ± 0.93) gm/dl. Mishra et al compared mini-PCNL and standard-PCNL for renal stones (1–2 cm), shows that mini PCNL has the advantage of reduced hemoglobin drop (0.8 ± 0.9 vs.1.3 ± 0.4) [2], their data is confirmed with our results that blood loss was less in mini-PCNL in comparison to standard-PCNL.

In present study there was statistically significant difference between the two groups regarding total complication rate, where the intra-operative bleeding was reported in standard-PCNL, perforation of the urinary system was reported 3 timed in standard-PCNL compared to one case in mini-PCNL(Table 2), our results are comparable with the results of Zhu et al and Qin et al [8, 10].

In the present study there were no changes of kidney function in mini-PCNL or standard-PCNL compared to pre-operative parameters. Earlier reports showed that PCNL has a minimal impact on global kidney function, could be conducted even in kidneys with some degree of functional impairment, and the procedure is recommended to prevent the development of complications.

Postoperative pain was higher among standard-PCNL (7.5 ± 1.1) versus (5.7 ± 0.7) in mini-PCNL with p values 0.0001. The systematic review and meta-analysis of Zhu et al [8] showed that only 3 studies were assessing postoperative pain using VAS and it was statistically significantly lower among mini- PCNL group. Same results were confirmed by Zeng et al [11], their data is in accordance of our finding that post-operative pain in mini-PCNL was lower compared to standard-PCNL.

The SFR was 80% and 85% in mini-PCNL and standard-PCNL respectively, this difference was not statistically significant. Zeng et al in a multicenter study comparing mini-PCNL versus standard-PCNL in treatment of renal stones larger than 2 cm, stated that SFR of mini-PCNL and standard-PCNL were presumed to be 83% and 89% [21]. Zhu et al reported that there was no difference between mini PCNL and standard PCNL in terms of stone free rate [8].The present study showed that SFR was comparable in both groups.

Definition of the SFR in different studies was slightly variable; in the present study a residual fragment less than 3mm with no stone related events were defined as SFR.

In the present study patients who undergone mini-PCNL or standard-PCNL did not encounter residual stones related events.