PCNL is reserved for larger and more complex kidney stone burdens and has almost completely replaced open stone surgery in this indication. Access to the collecting system is obtained either by interventional radiology prior to surgery or by the urologist intraoperatively with fluoroscopic guidance through a percutaneous tract directed through the flank.

This tract is then dilated and a sheath is placed to allow direct access to the collecting system with a nephroscope. The large caliber of this access sheath allows for powerful ultrasonic and hydraulic lithotripters and tools to grasp and remove large stone fragments. While still minimally invasive, this procedure does incur greater risks than ESWL and URS, including hemorrhage and renal pelvis perforation. Multiple tracts are placed for complex collecting system anatomy.

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Should a postoperative scan reveal residual stone burden, the same tract can be used for a second look PCNL. Use of open stone surgery, including anatrophic nephrolithotomy, is now only reserved for patients in whom PCNL has failed or rendered impossible because of patient anatomy.

Stones located in the kidney that are larger than 2 cm (cumulative stone burden) and staghorn calculi should be treated with PCNL. Lower pole kidney stones have low stone-free rates with ESWL and URS, regardless of size because fragments do not easily pass down the ureter. With URS, small stones can be moved from the lower kidney to the upper kidney, making URS the choice for small lower pole stones.

Stones smaller than 1cm not located in the lower pole can usually be treated effectively with ESWL. Stones 1-2 cm that are not in the lower pole, less than 1000 Hounsfield units (HFU) on computed tomography scans, and with a short skin to stone distance (less than 10 cm) also can be effectively treated with ESWL. Harder 1-2 cm stones (greater than 1000 HFU) can be treated with URS/laser lithotripsy.

Stones in the ureter are generally treated with URS. ESWL can be used for stones at the most upper portions of the ureter. PCNL for ureteral stones is reserved for very large stones at the ureteropelvic junction or proximal ureter. While ESWL is often the treatment modality preferred by patients as it is the least invasive, ureteral stone free rates are higher with ureteroscopic lithotripsy, especially as stone density and size increases. For this reason ureteroscopy is considered the gold standard for ureteral stones.

Dr. Conti is a urology resident and Dr. Chung is Assistant Professor of Urology, Director of Robotic and Minimally Invasive Urologic Surgery, Stanford University School of Medicine.

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