To compare the safety and efficacy of minimally invasive percutaneous nephrolitholapaxy (MIP) between small (<2 cm) and large (>2 cm) renal calculi, because although MIP has proved its efficacy in small lower caliceal stones, the efficacy in large renal calculi has been questioned.

The data from 191 consecutive minimally invasive percutaneous nephrolithotomy (MIP) procedures at a single institution from January 2007 to March 2011 were reviewed retrospectively. All stone sizes and complexity were included (98 were <2 cm and 93 were ≥2 cm). We performed a comparative analysis of procedures for calculi <2 cm and ≥2 cm regarding the stone-free rate, the need for auxiliary procedures, and complications. The Student t test for parametric continuous variables and the chi-square test or Fischer’s exact test for nominal variables were applied.

The primary stone-free rate was significantly lower for the large than for the small stones (76.3% vs 90.8%, P = .007), and the secondary stone-free rate after one auxiliary procedure (second-look percutaneous nephrolithotomy, ureterorenoscopy, or shock wave lithotripsy) was not significantly different between the 2 groups (94.6% vs 98.9%, P = .1). The total complication rate was not significantly different (26.9% vs 19.4%, P = .2) between the 2 groups either. Grade III complications occurred in 5.2% of all patients, and no grade IV or V complications were observed.

Using MIP, the total stone-free rate was greater for the small than for the large calculi; however, most patients could be rendered stone-free with the use of one auxiliary procedure. The high success rate and low rate of higher grade complications justify the application of MIP for large stones.