Category: Clinical Stones: PCNL
Introduction & Objective : To determine the stone clearance rates of multi-scope PCNL and assess the accuracy of intraoperative stone-free prediction as compared to postoperative CT scan.
Methods : A prospectively maintained database of multi-scope PCNL was queried for procedures performed 8/2017 to 1/2018. Retrograde access was performed using an 11/13fr 36cm sheath and flexible URS. Percutaneous access was guided by endoscopy and fluoroscopy. PCNL was performed through a 30fr (standard) or 18fr (minimally invasive PCNL, or MIP) sheath in prone position. At the end of each procedure, patients’ residual stone status was estimated. To verify or refute this estimation, a CT scan was performed on the first post-operative or prior to stent removal. Stone-free was defined as no single stone >4mm on CT. Characteristics of stone-free patients and accurately-estimated patients were analyzed using t-tests and logistic regression.
A total of 110 procedures were reviewed. Average age was 58.9 ± 12.6 years (range 26-87) and 69 (63%) were male. The mean stone size was 33.3 ± 23.5 mm (range 4-140mm). PCNL access was standard in 94 (85.5%) and MIP in 16(14.5%). Ambulatory Surgery Center procedures were done in 58 (52.7%) and 52(47.3%) were conducted in the hospital. Ninety-three patients (84.5%) were endoscopically estimated to be stone free, of which 84 (90% of predicted SF cohort, 76% of total cohort) were confirmed stone free via CT scan.
The twenty-six patients (24%) with residual stones had significantly larger preoperative stone burdens than those who were stone-free (48.4 ± 5.7 vs 28.5 ± 2.1 mm, p<0.0001). The mean residual stone size was 12.2 ± 8.0 mm. Of those patients with residual stones, 9 underwent URS, 7 underwent PCNL and 10 were observed. Patients predicted to be stone free but had RF's on post op CT scan had a mean stone size of 7.6mm (range 4-8). The sensitivity for estimating stone-free status with multi-scope PCNL was 65.4% (95%CI 44.3-82.8%), specificity was 100% (95CI 95.7-100.0%) and accuracy was 91.8% (95%CI 85.0-96.2%)
Logistic regression revealed that preoperative stone burden and fluoroscopy time were the only factor associated with residual stones on postoperative CT (OR 1.03, 95%CI 1.01-1.05, p = 0.0004 and OR 1.01, 95%CI 1.0-1.02, p = 0.0081 respectively). The type of access sheath, BMI, age and the location of procedure were not independent predictors of either endpoint.
Conclusions : Multi-scope PCNL can accurately predict clinical stone free status and may obviate the need for additional CT scans. Consistent with prior studies, the primary determinant of residual stone after PCNL is initial stone size.
Julio Davalos– Director Kidney Stone Program, Chesapeake Urology, Baltimore, Maryland
Mark Silva– Endourology Fellow, Chesapeake Urology, New York, New York
Alex Small– Columbia University Medical Center, New York, New York
Joel Abbott– Endourologist, Chesapeake Urology, Baltimore, Maryland
New York, New York
Mark V. Silva, MD
NYU Dept. of Urology
New York, NY