To evaluate intraoperative decision making regarding the necessity of second-look nephroscopy after percutaneous nephrolithotomy.

Percutaneous nephrolithotomy was performed cooperatively by a urologist and radiologist equipped with a high-resolution C-arm. Ultrasonic lithotripsy was performed followed by thorough flexible nephroscopy and fluoroscopy. At conclusion patients were prospectively classified as radiologically and/or endoscopically stone free. If confident that complete stone clearance had been atruamatically achieved, a ureteral stent was placed. If there was suspicion of trauma or residual calculi, a nephrostomy tube was inserted. Postoperative CT was performed and allowed fragment classification as stone free, less than 2 mm, 2 to 4 mm, or 4 mm or greater.

Average stone dimensions were 640.2 ± 412.5 mm² in 39 consecutive renal units. Computed tomographic imaging demonstrated that 26 renal units (66.7%) were stone free after primary procedure, with 5 (12.8%), 5 (12.8%), and 3 (7.7%) having fragments less than 2 mm, 2 to 4 mm, and greater than 4 mm, respectively. Of the 34 renal units considered endoscopically and fluoroscopically stone free, postoperative CT demonstrated 9 with residual fragments, all less than 4 mm. Of the 5 renal units not considered radiologically and endoscopically stone free, 4 had fragments on CT. Nephrostomy tubes were avoided in 33 patients. This intraoperative decision was supported by negative predictive values of 100%, 88%, and 73% at postoperative CT fragment detection thresholds of 4 mm, 2 mm, and 0 mm, respectively.

Rigorous fragment detection allows confident intraoperative decision making regarding the necessity of second-look nephroscopy.