Percutaneous Nephrolithotomy in the Modified Flank Free Supine Position: An Observational Prospective Study to Identify the Surgeon’s Learning Curve

Abstract

Background: Percutaneous nephrolithotomy was usually practiced in prone position. However, there is a recent shift towards supine position. This shift needs a continuous practice to increase the surgeon’s learning curve. Aims: To give an insight into the learning curve of a single surgeon, capable of doing percutaneous nephrolithotomy in the conventional prone position, during his transition to the supine one using different indicators. Materials and Methods: This study included 80 procedures, equally divided into 4 groups and the following endpoints were recorded and compared among groups: operation and fluoroscopic screening times, volume of the irrigant fluid consumed, postoperative length of hospital stay, stone clearance rate and procedure related morbidity. Results: The mean operation and fluoroscope screening durations showed a statistically significant decline with time. The operative time drop from 117 minutes at the beginning to about the half [60 minutes] after sixth months and working with 80 patients. The fluoroscopy time declined from 3.5 minutes at the beginning to 1.5 minute at the end. Our stone clearance rate continued to improve among groups [with advancement of learning curve] [P = 0.034] without approaching the plateau. Also for other indicators [volume of the irrigant fluid consumed, postoperative length of hospital stay and complications], all showed statistical significant reduction with increased learning curve [P < 0.0001]. Conclusions: Operative time and stone clearance rate continued improvement with increasing learning curve. However, the volume of irrigation fluid, rate and grade of complications and length of postoperative stay reached its plateau after 40 procedures.

Keywords

• conventional prone position
• learning curve
• modified flank free supine position
• percutaneous nephrolithotomy
• urinary stones