Percutaneous nephrolithotomy (PCNL)

Percutaneous nephrolithotomy (PCNL), first introduced in the 1970s as a minimally invasive alternative to open stone surgery, is now the gold standard for managing large and complex renal calculi. Its core principle—percutaneous access to the renal collecting system for stone removal—remains unchanged, but nearly every aspect of the procedure has evolved through advances in technology, miniaturisation, and safety optimisation. This overview summarises the current role of PCNL in nephrolithiasis management and highlights recent developments such as miniaturised techniques, suction-assisted systems, laser lithotripsy, and image-guided navigation. It also examines how these innovations have improved stone-free rates, efficiency, and safety across diverse patient groups.

The Current Role of PCNL in Nephrolithiasis Management

Historical Evolution

Since its introduction under radiologic guidance in the 1970s, PCNL has replaced open anatrophic nephrolithotomy for most large-stone cases. It is now the preferred treatment for patients with large stone burdens, complex anatomy, or stones resistant to shock wave lithotripsy (SWL) or ureteroscopy (URS).

Indications for PCNL

Both the European Association of Urology (EAU) and American Urological Association (AUA) recommend PCNL as first-line therapy for: 

Stone Size and Burden

• >20 mm: Gold standard; highest likelihood of single-session clearance.

• Staghorn calculi: Most effective and often the only feasible option, sometimes requiring multiple tracts or staged procedures.

• 10–20 mm: Considered when SWL or RIRS have low expected success, especially in the lower pole or with dense/unfavourable stones.

Stone Location and Anatomy

• Lower pole stones >10 mm: PCNL preferred when infundibular anatomy reduces SWL efficacy.

• Anomalous kidneys: Safe and effective in horseshoe, ectopic, and malrotated kidneys with adjusted access techniques.

• Special populations: Mini-PCNL variants are well-suited for children, obese patients, solitary kidneys, and those with urinary diversions.

Patient-Related Factors

• Comorbidities: Can be performed supine or under regional anaesthesia for patients with cardiopulmonary risk.

• Infection: Active infection is a contraindication; urine must be sterilised preoperatively.

Comparative Effectiveness

PCNL achieves higher stone-free rates than SWL or RIRS for large and complex stones, with fewer secondary procedures required. Although associated with slightly higher complication risks, mini-PCNL has demonstrated superior clearance for 10–20 mm lower pole stones compared with SWL and RIRS.

Expanding Indications

Miniaturisation and improved imaging have broadened PCNL’s use to:

• Smaller stones

• Paediatric patients

• Challenging anatomies (e.g., horseshoe, ectopic, or transplanted kidneys)

It is now routinely and safely performed across both adult and paediatric populations with technique modifications to reduce morbidity.

Traditional Standard PCNL Technique and Outcomes

Standard Technique

The classic PCNL involves:

1. Preoperative Imaging: Non-contrast CT for stone mapping, anatomy, and surgical planning.
2. Patient Positioning: Traditionally prone, but supine and modified positions are increasingly used. Galdakao-Modified Valdivia position combines supine and lithotomy, allowing simultaneous ureteroscopic and percutaneous access. while the Lateral/Flank position Used in select cases, especially in Paediatric or complex anatomy.
3. Access: Percutaneous puncture of the desired calyx under fluoroscopic and/or ultrasound guidance.
4. Tract Dilation: Serial or balloon dilation to 24–30 Fr, followed by placement of a rigid nephroscope.
5. Stone Fragmentation: Pneumatic, ultrasonic, or laser lithotripsy.
6. Fragment Retrieval: Graspers, baskets, or suction.
7. Exit Strategy: Placement of a nephrostomy tube, stent, or tubeless approach.

Outcomes

• Stone-Free Rates: 85–95% for large stones, higher for single stones and lower for staghorn or complex stones.
• Complications: Bleeding (transfusion rates 3–6%), fever (10–16%), sepsis (0.5–2%), injury to adjacent organs (rare), and urinary leakage.
• Hospital Stay: Traditionally 2–4 days, but decreasing with tubeless and ambulatory approaches.

Limitations

Standard PCNL, while highly effective, is associated with greater morbidity—particularly bleeding and longer recovery—compared to Miniaturised techniques, prompting the development of less invasive variants.

Advances in PCNL

1. Miniaturized PCNL

• Mini-PCNL (14–20 Fr): Balances efficacy with reduced bleeding and pain.
• Ultra-mini-PCNL (11–13 Fr): Suited for moderate stones; less invasive.
• Micro-PCNL (4.8 Fr): Needle puncture with laser lithotripsy; ideal for small stones.
• Impact: Lower morbidity, outpatient feasibility, tailored to stone size.

2. Energy Sources

• Laser lithotripsy (Holmium:YAG, Thulium fiber): Precise fragmentation, effective for hard stones.
• Combination devices: Ultrasound + suction systems improve clearance and reduce operative time.

3. Suction-Assisted Technologies

• Continuous aspiration during lithotripsy improves visibility, reduces intrarenal pressure, and lowers infection risk.

4. Imaging and Navigation

• Ultrasound-guided access: Minimizes radiation exposure.
• CT-based planning: Improves accuracy in complex anatomy.
• Robotic and computer-assisted navigation: Emerging tools for precision puncture and tract creation.

5. Tubeless and Ambulatory PCNL

• Selected patients discharged same day with no nephrostomy tube.

Reduced pain, faster recovery, lower healthcare costs.

Future Directions and Ongoing Trials/Registries in PCNL

Ongoing Registries and Trials

• STUMPS Registry: Global prospective registry evaluating suction mini-PCNL, providing real-world data on equipment, strategies, and outcomes.
• FANS Registry: Flexible and Navigable Suction Access Sheath in Ureteroscopy registry, comparing suction-assisted RIRS and PCNL.
• Robotic Trials: Ongoing studies evaluating robotic-assisted access, navigation, and integration with AI for improved precision and safety.

Technological Innovations

• 3D Navigation and Mixed Reality: Integration of preoperative imaging, real-time navigation, and holographic overlays to enhance access accuracy and reduce complications.
• Artificial Intelligence: AI-driven planning and intraoperative support for access, stone clearance prediction, and complication risk stratification.
• Advanced Lithotripsy: Development of more efficient and safer laser systems (e.g., TFL, Moses technology) and automated suction devices.

Standardization and Reporting

• Outcome Reporting: International efforts (e.g., IAU checklist) to standardize reporting of PCNL outcomes, complications, and procedural details to facilitate benchmarking and research.