Residency · Residency · Urology

Percutaneous Nephrolithotomy: Access and Technique

Indications

Percutaneous nephrolithotomy (PCNL) is primarily indicated for renal stones larger than 20 mm, aligning with the first-line recommendations from the American Urological Association (AUA) and European Association of Urology (EAU). It is also the preferred treatment for partial or complete staghorn calculi, as well as lower-pole stones exceeding 10 mm, particularly when the anatomy is unfavorable for shock wave lithotripsy (SWL). PCNL is utilized in cases where SWL or ureteroscopy (URS) has failed or when stones are resistant to these modalities. Stones located within calyceal diverticula may require combined access and diverticulotomy via PCNL. Additionally, cystine stones or other compositions resistant to SWL, especially when large, are suitable for this approach. Stone-free rates after PCNL range from 75% to 95%, depending on the stone burden and complexity.

Preoperative Planning

Imaging

Non-contrast computed tomography (CT) is essential for assessing stone burden, location, number, density measured in Hounsfield units (HU), and the anatomy of the collecting system. Contrast-enhanced CT or CT urography further delineates calyceal anatomy and helps identify posterior calyces optimal for access. It is critical to evaluate for the presence of a retrorenal colon, which occurs in 5-10% of patients and is more common on the left side, especially near the lower pole. The relationship of the pleural reflection to the 12th rib must be assessed to anticipate the risks associated with supracostal access. The positions of the spleen and liver relative to the planned access site should also be reviewed, along with renal vascular anatomy and any anomalies.

Patient Optimization

Prior to PCNL, urine culture is mandatory to identify and treat any active infections, ensuring sterile urine before elective procedures. Anticoagulation should be discontinued according to guidelines due to the high bleeding risk associated with PCNL. Prophylactic antibiotics, typically a single dose of a fluoroquinolone or aminoglycoside combined with ampicillin, are administered to reduce infection risk. Blood typing and crossmatching are performed as transfusion rates range from 2% to 5%.

<image>CT-based preoperative planning for PCNL showing ideal posterior calyceal access trajectory, retrorenal colon assessment, and rib/pleural relationships</image>

Positioning

Prone Position (Standard)

The prone position is the most commonly used for PCNL because it provides the widest access to the posterior calyces. The patient is positioned on chest bolsters or a frame with the abdomen free to reduce venous pressure. This position offers full posterior access and familiar fluoroscopic anatomy. However, it presents challenges in airway management, limits access for combined ureteroscopy, and may have hemodynamic effects due to prone positioning.

Supine Position (Modified Valdivia/Galdakao)

In the supine position, the patient lies on their back with the ipsilateral flank elevated 20 to 30 degrees. This approach facilitates easier airway management and allows simultaneous retrograde access for combined endoscopic combined intrarenal surgery (ECIRS). It also promotes hemodynamic stability and can reduce operating room time. The disadvantages include limited posterior calyceal access, a narrower working space, and a steeper learning curve. Evidence suggests that stone-free rates and complication rates are similar to the prone position when performed by experienced surgeons.

Lateral Decubitus

The lateral decubitus position is less commonly used but may be advantageous in specific anatomic situations.

Access Techniques

Fluoroscopic-Guided Access

Fluoroscopic guidance is the most widely used method globally. A retrograde pyelogram is performed via a ureteral catheter to opacify the collecting system. The triangulation technique involves using a 0-degree anteroposterior fluoroscopic view to identify the target calyx, followed by a 30-degree tilt to confirm the posterior location. The needle is then advanced through the posterior calyx at the desired angle. The "bull's-eye" technique involves aligning the fluoroscope along the needle trajectory for precise puncture. The target is the posterior calyx fornix, which avoids interlobar vessels located in Brodel's avascular line, minimizing bleeding risk.

Ultrasound-Guided Access

Ultrasound guidance provides real-time visualization of the needle trajectory and surrounding structures such as the colon and pleura, eliminating radiation exposure. It allows simultaneous visualization of the needle and kidney, enhancing safety. Growing evidence supports that ultrasound-guided access is comparable or superior in safety to fluoroscopy alone. It can also be combined with fluoroscopy for dual guidance.

CT-Guided Access

CT-guided access is reserved for complex anatomical scenarios such as horseshoe kidneys, ectopic kidneys, or morbid obesity. Although it involves higher radiation exposure, it offers precise localization.

Urologist-Obtained vs. Radiology-Obtained Access

There is a trend toward urologists performing access themselves to improve efficiency by enabling a single-stage procedure. Radiology-obtained access may be performed the day before surgery, requiring two separate procedures. Training in access techniques is increasingly incorporated into endourology fellowships.

Tract Dilation

Methods

Serial Amplatz dilators, which are sequential metal dilators ranging from 8 to 30 French (Fr), are the most common method for tract dilation. Balloon dilators provide single-step dilation to 30 Fr and are faster but more expensive. Alken metal telescopic dilators use a coaxial telescoping metal system. The standard tract size ranges from 24 to 30 Fr, allowing the use of a standard nephroscope.

Sheath Placement

An Amplatz sheath sized 24 to 30 Fr is placed over the dilators to maintain access. This sheath provides a tamponade effect on the tract, reducing bleeding, and allows repeated insertion of the nephroscope during the procedure.

<image>Step-by-step illustration of fluoroscopic-guided percutaneous renal access showing needle puncture of posterior calyx, guidewire placement, serial dilation, and Amplatz sheath insertion</image>

Nephroscopy and Stone Treatment

Rigid Nephroscopy

The primary instrument used is a 24 to 26 Fr rigid nephroscope, which provides direct visualization with continuous irrigation. Its working channel accommodates lithotripsy devices and graspers for stone fragmentation and removal.

Lithotripsy Devices

Ultrasonic lithotripters use a vibrating probe to fragment stones while simultaneously aspirating debris, making them excellent for large stones. Pneumatic (ballistic) lithotripters employ compressed air-driven probes that are effective but lack suction capability. Combined dual-energy devices, such as the Swiss LithoClast or CyberWand, integrate ultrasonic and pneumatic technologies, offering the most efficient fragmentation for large or hard stones. Holmium or thulium fiber lasers (TFL) can be used via flexible nephroscopes to treat residual fragments in inaccessible calyces.

Flexible Nephroscopy

Flexible nephroscopy is performed through the Amplatz sheath to inspect all calyces thoroughly. This step is essential for achieving a stone-free status and is often combined with laser lithotripsy to manage residual fragments.

Exit Strategies

Standard (Nephrostomy Tube)

The standard exit strategy involves placing a large-bore (18-22 Fr) re-entry Malecot or Foley catheter nephrostomy tube. This provides tamponade of the tract, allows access for a second-look procedure if needed, and facilitates antegrade nephrostograms. The nephrostomy tube is typically removed 24 to 48 hours postoperatively after confirming no residual fragments or urinary leakage.

Tubeless PCNL

Tubeless PCNL involves placing only a ureteral stent without a nephrostomy tube. This approach is suitable for uncomplicated procedures without significant bleeding, residual stones requiring a second look, or perforation. Tubeless PCNL reduces postoperative pain, analgesic requirements, and hospital stay. Multiple randomized controlled trials support its safety in selected patients.

Totally Tubeless PCNL

Totally tubeless PCNL omits both the nephrostomy tube and ureteral stent. This approach is reserved for the most selective cases: completely uncomplicated, stone-free procedures with no bleeding and single access. Emerging data suggest that it is feasible and further reduces morbidity.

Mini-PCNL and Ultra-Mini-PCNL

Mini-PCNL (14-22 Fr)

Mini-PCNL uses smaller tracts and instruments, resulting in less bleeding and reduced renal parenchymal damage, potentially shortening hospitalization. However, it may require longer operative times for large stones and has reduced fragment clearance efficiency. It is best suited for stones measuring 10 to 25 mm.

Ultra-Mini-PCNL (11-13 Fr)

Ultra-mini-PCNL, also known as micro-PCNL, uses tracts sized 11 to 13 Fr. It is indicated for stones 10 to 20 mm and combines the benefits of minimal access with direct nephroscopic visualization.

Super-Mini-PCNL (SMP) and Micro-PCNL (<10 Fr)

These are investigational techniques that blur the line between ureteroscopy and PCNL. They rely on drainage through the tract via natural hydrostatic pressure.

<image>Comparison of tract sizes in standard PCNL (30 Fr), mini-PCNL (16-18 Fr), and ultra-mini-PCNL (11-13 Fr) with corresponding instruments</image>

Complications

Bleeding is the most common significant complication of PCNL, with transfusion rates between 2% and 5%. Delayed hemorrhage may result from arteriovenous fistula or pseudoaneurysm formation, diagnosed by CT angiography and treated with selective angioembolization. Intercostal artery injury can occur with supracostal access. Infection and sepsis occur in 1% to 3% of cases, with increased risk in patients with infected stones, prolonged operative times, or high intrarenal pressures. Collecting system perforation or extravasation occurs in 5% to 8% of cases and is usually managed conservatively with ureteral stenting or nephrostomy drainage. Pleural injury, including pneumothorax (2-4% incidence with access above the 12th rib) and hydrothorax, can occur with supracostal access; postoperative chest X-rays are mandatory in these cases, and chest tube placement is required if symptomatic. Colonic injury is rare (<0.5%) and typically involves a retrorenal colon; management includes nephrostomy removal and antibiotics, with most cases healing without surgery. Rare injuries to adjacent organs such as the spleen or liver have been reported. Retained stone fragments occur in 10% to 25% of cases and may necessitate second-look flexible nephroscopy or staged ureteroscopy.

Clinical Pearls

Access is the most critical step in PCNL, as a well-placed tract through the target calyx fornix largely determines procedural success. Increasingly, urologists perform access themselves, making hands-on training during fellowship essential. The principle of slow shock rate applies to PCNL as well; minimizing intrarenal pressures during nephroscopy reduces pyelovenous backflow and the risk of sepsis. Preoperative CT should always be reviewed carefully for retrorenal colon, especially when planning left lower-pole access. Supracostal access above the 12th rib offers better reach to upper-pole and staghorn stones but carries a risk of pneumothorax, necessitating a postoperative chest X-ray. Tubeless PCNL is safe and evidence-based in uncomplicated cases, significantly reducing pain and hospital stay. Finally, second-look flexible nephroscopy performed 48 to 72 hours postoperatively through the existing tract improves stone-free rates in complex stone burdens.

References

• AUA/Endourology Society Guideline on Surgical Management of Stones, 2016 (amended 2022)
• EAU Guidelines on Urolithiasis, 2024 Update
• de la Rosette J, et al. "The Clinical Research Office of the Endourological Society PCNL Global Study." J Endourol. 2011;25(1):11-17.
• Desai M, et al. "Supine versus prone PCNL: a systematic review." J Endourol. 2014.
• Lahme S, et al. "Miniaturized PCNL." World J Urol. 2015.
• Campbell-Walsh-Wein Urology, 12th Edition, Chapter on Percutaneous Management of Renal Calculi

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