Kidney stones that are large or complex are often treated with percutaneous nephrolithotomy, also called PCNL. Standard PCNL uses a larger access tract and is effective for removing complex kidney stones, but it may be associated with more bleeding, pain, and recovery burden. Modified mini-PCNL uses a smaller access tract and may reduce surgical trauma while maintaining a similar stone clearance rate.

This multicenter randomized trial will compare modified mini-PCNL using a 20 Fr access sheath with standard PCNL using a 24 Fr access sheath in adults with complex renal stones. About 1,380 participants from 8 urology centers will be randomly assigned to receive one of the two procedures. The main purpose of the study is to determine whether modified mini-PCNL is not worse than standard PCNL in achieving stone-free status shortly after surgery. Stone-free status will be assessed by low-dose noncontrast CT within 72 hours after surgery. The study will also compare stone-free status at 3 months, complications, operation time, length of hospital stay, need for additional procedures, and quality of life.

Inclusion Criteria:

1. Adults aged ≥18 years.
2. Serum creatinine ≤133 μmol/L.
3. American Society of Anesthesiologists (ASA) physical status classification I-III.
4. S.T.O.N.E. score ≥8.
5. Complex renal stones confirmed by noncontrast computed tomography, including stone surface area >1500 mm², multiple calyceal stones, partial or complete staghorn calculi, or complex anatomical conditions.
6. Patients who provide written informed consent and agree to undergo either modified mini-percutaneous nephrolithotomy or standard percutaneous nephrolithotomy.

Exclusion Criteria:

1. Solitary kidney.
2. Morbid obesity (body mass index ≥35 kg/m²).
3. Previous renal transplantation or urinary diversion.
4. Congenital abnormalities of the urinary tract.
5. Pregnancy.
6. Uncorrected coagulopathy.
7. Active urinary tract infection.