Effective and safe percutaneous access is the cornerstone of successful percutaneous nephrolithotomy (PCNL). Calyceal puncture sites are carefully selected based on patient and stone characteristics to maximize rigid nephroscopy and stone removal and minimize complications. The preferred access–upper vs lower pole–for the complex stone is yet to be determined, but each has different anatomical considerations and complications related to access selection.

Lower pole percutaneous access is most commonly performed. This site is selected based on ease of subcostal access to the lower pole and historically lower complication rates. Lower pole calyceal stones are usually approached through the posterior inferior calyx, which typically coincides with an avascular plane between the anterior and posterior renal divisions. Subcostal access is obtained medial to the posterior axillary line to avoid injury to adjacent organs such as the colon. The ribs and pelvis are often sufficiently far away that they do not limit selection of access trajectory.¹ Tefleki et al reviewed the data of 4494 patients undergoing PCNL at 96 global centers collected by the Clinical Research Office of the Endourological Society. Lower pole access was performed for 69% of cases (vs 9% upper pole access alone) with reported complication rate of 16% (vs 23%), including 3% (vs 5%) major complications.²

Despite the relative ease of access, lower pole calyces can have more intricate structure, smaller internal volume, and larger angle with the kidney’s long axis. These anatomic constraints can cause problems in negotiating the acute angles between calyces (Figure 1).³ More torquing on the kidney can result in renal parenchymal trauma and increased risk of bleeding. Furthermore, a single percutaneous access may not be sufficient for complete stone clearance, and additional access tracts and/or extensive flexible nephroscopy may be required to treat all stones.⁴ However, similar rates of pelvicalyceal perforation, transfusion, operation time, length of stay, and postoperative infectious rates have been reported when compared to upper pole access.^4-6

Upper pole percutaneous access can permit better access into the collecting system and proximal ureter, but can be more technically challenging to obtain. The upper pole is typically aligned medially and posterior to the lower pole, making upper pole access often the shortest tract to the kidney.⁷ However, certain access tracts can be limited by the adjacent ribs. When upper pole access is aligned with the long axis of the kidney, the rigid nephroscope can be used to treat stones in the upper pole, lower pole, ureteropelvic junction (UPJ), and proximal ureter. This approach is often preferred for treatment of complex stones such as staghorn calculi as well as stones in patients with congenital renal anomalies such as horseshoe kidney (see Table). The ease of access with a rigid nephroscope can decrease the need for multiple access tracts and result in less manipulative trauma.^8,9 A recent meta-analysis by Huang et al reported better stone free rates with upper pole access.⁶

Upper pole access is associated with a higher rate of thoracic complications compared to lower pole access.² Hydrothorax has been attributed to entry into the pleural space during PCNL.⁸ The parietal pleura crosses the middle of the 12th rib posteriorly and the 11th rib at the posterior axillary line. Therefore, puncture above the 12th rib more inferior and lateral to the mid-scapular line has decreased risk of pleural injury (Figure 2). A supracostal percutaneous access may be necessary when the stone is located above the 12th rib even at full inspiration.⁸ Tefleki et al reported that intercostal punctures above the 11th rib were associated with a higher rate of hydrothorax than those above the 12th rib; however, there was no statistically significant difference between hydrothorax rates for punctures above and below the 12th rib.²

There are important limitations to our current literature comparing upper vs lower pole access. Most studies are retrospective reviews of heterogenous patient populations and typically performed at high-volume centers.

The optimal percutaneous access tract is required for maximum stone clearance during PCNL. However, preferred access location is highly dependent on patient and stone factors as well as surgeon experience. Therefore, the AUA guidelines for the surgical management of stones mandate the acquisition of CT imaging prior to PCNL in order to define renal anatomy and the relationship to adjacent structures as well as stone size and location.¹⁰ The upper pole is often parallel to the long axis of kidney which allows easier access to the renal pelvis and UPJ for improved stone clearance with a single access especially in cases of branched stones, but it is associated with a higher risk of thoracic complications. Lower pole percutaneous access has a lower risk of complications, but it can be difficult to access adjacent calyces or the UPJ, which may increase the risk of torque and injury to the kidney. Calyceal anatomy is even more crucial in patients with anatomic abnormalities such as morbid obesity, kyphoscoliosis, horseshoe kidneys, and ectopic or malrotated kidneys. These patients are at greater risk for more difficult access, incomplete stone removal, and injury to adjacent organs, making access selection a vital part of PCNL planning.