Mini Percutaneous Nephrolithotomy is Safe, Effective for Treatment of Renal Stones

Mini percutaneous nephrolithotomy (MPNL) appears to be similarly effective and as safe as standard percutaneous nephrolithotomy (SPNL) for the treatment of renal stones measuring 10 to 30 mm, yet MPNL may be associated with fewer bleeding events and less postoperative pain but longer operative time, according to a study presented at the 2021 American Urological Association Annual Meeting.

In this randomized controlled trial, researchers assigned patients with renal calculi between 10 and 30 mm to either MPNL (n=15) with laser dusting or SPNL (n=30) with pneumatic and/or ultrasonic stone disintegration.

Researchers assessed the immediate stone-free rate using non-contrast spiral CT (NCCT). The “stone-free” status was determined by the lack of stones or presence of stone <4 mm in maximum diameter. Additional endpoints for the study were operative time, post-operative complications, post-operative pain (visual analog scale [VAS]), patient satisfaction (as assessed by the Freiburg index of patient satisfaction [FIPS]), and hemoglobin drop.

The mean ages of patients in the MPNL and SPNL groups were 48.6 and 50.7 years, respectively (p=0.2). No significant difference was observed between the two groups in terms of body mass index (p=0.4), stone size (p=0.1), number of stones (p=0.4), or stone-free rate (p=0.08) at baseline.

In terms of intraoperative parameters, no difference was found between the two groups in regard to the puncture rate (97% vs. 96; p=0.7). Patients assigned to MPNL had a longer median operative time (74 vs. 60 minutes; p<0.001), lower postoperative mean VAS (3.4 vs 4.9; p<0.001), and lower mean FIPS score (9.6 vs 13.4; p<0.001).

The immediate stone-free rate was proportionally lower in the MPNL arm compared with the SPNL group (90.2% vs 96.2%, respectively; p=0.08). There was no notable difference between the two groups in terms of postoperative complications (p=0.2). Additionally, no difference was observed in the mean hemoglobin drop (0.7 vs 1.1 mg/dl; p=0.006).

Given these findings, the researchers suggest that while MPNL may show similar efficacy and safety as SPNL, clinicians should be aware of the longer operative time. Whether the longer duration associated with MPNL outweighs the observed benefits may require future study.