January 1, 2012
Although percutaneous nephrolithotomy (PCNL) comprises only 4% to 6% of all stone surgeries (J Urol 2005; 173:848-57), it behooves the urologist with an interest in stone disease to be facile in this treatment modality in order to offer patients the most appropriate and effective treatment for their stones. This article focuses on the technical details of our approach to PCNL, from preoperative imaging to postoperative care.
Thorough delineation of the location and extent of the stone as well as of the intrarenal and relational anatomy of the kidney is critical to successful PCNL. Intravenous urography (IVU) and non-enhanced computed tomography provide complementary information that together provide an accurate assessment of stone burden and location within the collecting system as well as establish the position of the kidney in relation to surrounding visceral organs such as the pleural space and colon (figure 1) (Urol Clin North Am 2006; 33:353-64; J Urol 2003; 170: 45-7).
Positioning, retrograde catheter placement
The anesthetized patient is placed prone in the split-leg position to enable simultaneous access to the flank and perineum (figure 2). A retrograde ureteral catheter is placed to opacify the collecting system and prevent antegrade migration of fragments. We use a 7F, 11.5-cm occlusion balloon catheter (Boston Scientific, Natick, MA) passed through a 22F Councill catheter, as it provides optimal occlusion of the ureteropelvic junction (UPJ) and maximal distension of the collecting system for access. The occlusion balloon catheter is carefully inflated just above the UPJ with 1 cc of dilute contrast.
Opacification of the collecting system with air or contrast allows identification of the optimal calyx for percutaneous puncture. We prefer an air pyelogram, as contrast may obscure the stone and extravasated contrast can obscure the calyces. Gentle injection of 5 to 15 cc of air will preferentially delineate the posterior calyces as the air rises (figure 3). Rare cases of air embolism have been described with both air and contrast pyelograms, underscoring the need to avoid overdistension of the collecting system.
Selecting the optimal calyx for puncture
Percutaneous puncture directly into a posterior polar calyx (upper or lower) generally provides optimal access to the collecting system and minimizes the amount of parenchyma traversed by the tract. Guidewire access from an anterior calyx to the renal pelvis and ureter is more difficult because of the unfavorable acute angle. Access via an upper pole posterior calyx risks transgression of the pleural space, although it provides optimal access for staghorn stones occupying the entire collecting system, for stones occupying multiple lower pole calyces, and for large UPJ or proximal ureteral calculi. Because the upper pole of the kidney lies more posterior than the lower pole, access to the renal pelvis follows a less acute angle, thereby necessitating less torque on the nephroscope. Mid renal access is generally avoided as access to both the upper and lower pole calyces can be challenging from this location.