13.3 Percutaneous Nephrolithotomy (PCNL) & Endourological Safety

Percutaneous Nephrolithotomy (PCNL) & Endourological Safety

Percutaneous nephrolithotomy (PCNL) is the cornerstone intervention for massive and complex renal calculous disease. Since its introduction by Fernström and Johansson in 1976, PCNL has provided the highest stone-free rates among all stone interventions. However, traversing the vascular renal parenchyma directly into the pelvicalyceal system carries substantial physiological risks. Urologists must possess deep mastery of renal vascular anatomy, patient positioning, imaging-guided puncture, dilation dynamics, and the prompt management of severe vascular, visceral, and septic complications in accordance with European Association of Urology (EAU) guidelines.

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Indications for PCNL

According to international and EAU guidelines, PCNL is first-line for large renal stones and an important option in selected smaller or complex cases:

• Calculi $> 20$ mm: Large renal pelvis, calyceal, or staghorn / partial staghorn calculi. Stone burdens exceeding 20 mm achieve superior stone-free rates in fewer operative sessions with PCNL compared to flexible URS or SWL.
• Lower Pole Calculi $> 10 - 15$ mm with Unfavorable Anatomy: Poor lower-pole drainage reduces SWL clearance, and difficult anatomy can also limit RIRS. PCNL offers direct access, while RIRS remains an alternative; balance clearance against bleeding risk and invasiveness.
• Stones Resistant to Comminution: Brushite and cystine resist SWL. PCNL or RIRS may be selected according to burden and anatomy rather than composition alone.
• Calculi in Anatomical Anomalies: Horseshoe kidneys, ectopic kidneys and calyceal diverticula require individualized access planning; PCNL is one option when a safe tract is available.
• Stones Associated with Pelviureteric Junction Obstruction (PUJO): PCNL can combine stone extraction with selected endopyelotomy. The obstruction itself may instead require pyeloplasty, with concomitant stone removal.

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Patient Positioning: Prone vs. Supine PCNL

Surgical positioning profoundly impacts anesthetic safety, visceral proximity, and endourological maneuverability:

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|                                    PCNL POSITIONING MODALITIES                                     |
|                                                                                                    |
|  1. PRONE PCNL (Traditional Standard)                                                              |
|     - Large posterior flank working area                                                           |
|     - Extensive rotational excursion for rigid nephroscopes                                        |
|     - Ample room for multi-tract access (upper, middle, lower calyces)                             |
|     - Limitations: Cervical / ocular pressure; impaired cardiopulmonary mechanics;                 |
|       requires repositioning after retrograde catheterization; ECIRS requires a suitable modified  |
|       position                                                                                     |
|                                                                                                    |
|  2. SUPINE PCNL (Galdakao-Modified Valdivia Position)                                              |
|     - Flank elevated; modified lithotomy permits retrograde access                                 |
|     - Single positioning (no intraoperative turning required)                                      |
|     - Direct, simultaneous anterograde and retrograde access (ECIRS)                               |
|     - Easier airway access; dependent drainage can aid fragment evacuation                         |
|     - Colonic displacement: Abdominal viscera fall anteriorly, minimizing retrorenal colon injury  |
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1. Prone Positioning

• Technique: The patient is initially positioned in dorsal lithotomy to place an open-ended retrograde ureteral catheter for contrast opacification. The anesthetized patient is carefully turned prone onto appropriate supports, maintaining and checking the airway throughout repositioning.
• Advantages: Provides a broad surface area on the posterior and lateral abdominal wall; allows unrestricted instrument manipulation; facilitates straightforward upper pole, middle pole, and multi-tract punctures.
• Disadvantages: Repositioning an anesthetized, intubated patient carries risks of cervical spine injury, endotracheal tube dislodgement, and ocular/facial pressure neuropraxia. In obese patients, prone positioning restricts diaphragmatic excursion, diminishes lung compliance, and compresses the inferior vena cava, increasing epidural venous pressure and intraoperative parenchymal bleeding.

2. Supine Positioning (Galdakao-Modified Valdivia)

• Technique: The patient lies supine with the ipsilateral flank elevated 15° to 30° using a soft wedge, and the ipsilateral leg extended and the contralateral leg flexed and abducted for retrograde access.
• Key Advantages:
  • No Repositioning: Catheterization and PCNL can be performed without turning the patient, simplifying airway access and reducing repositioning time and pressure-related hazards.
  • Endoscopic Combined Intrarenal Surgery (ECIRS): Allows two surgeons to work simultaneously: one operating a flexible ureteroscope retrogradely from below, while the other operates a percutaneous nephroscope anterogradely from above. The retrograde scope can inspect inaccessible calyces, basketing stones and delivering them directly to the rigid nephroscope for ultrasonic destruction ("pass-the-ball" technique).
  • Cardiopulmonary Mechanics: Can be advantageous when airway access or cardiopulmonary reserve is a concern. Select positioning with the anesthetist; neither position guarantees normal ventilation or is universally safest.
  • Visceral Clearance: Gravity pulls the colon and small intestine anteriorly, theoretically widening the retroperitoneal working space and reducing the risk of accidental colonic injury.
  • Low Intrarenal Pressure: Dependent downward trajectory of the nephrostomy sheath promotes gravity-assisted drainage of irrigation fluid and stone dust.

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Percutaneous Puncture & Renal Vascular Anatomy

Safe renal access requires navigating the intricate three-dimensional arterial vasculature of the kidney:

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|                                    RENAL VASCULAR ANATOMY & BRÖDEL                                 |
|                                                                                                    |
|  Main Renal Artery --> Anterior Division (75% blood supply) & Posterior Division (25%)             |
|                                                                                                    |
|  Interlobar Arteries run along sides of calyces in the renal columns (Columns of Bertin)           |
|                                                                                                    |
|  AVASCULAR LINE OF BRÖDEL:                                                                         |
|  - Longitudinal plane of relative avascularity situated 1 to 2 cm posterior to lateral renal border|
|  - Boundary between anterior and posterior arterial arborizations                                  |
|                                                                                                    |
|  CORRECT PUNCTURE TRAJECTORY:                                                                      |
|  - Posterior calyceal puncture along a transpapillary trajectory                                   |
|  - Enters end-on while reducing the chance of major vessel injury                                  |
|                                                                                                    |
|  CATASTROPHIC ERROR:                                                                               |
|  - Central pelvic or infundibular puncture risks major interlobar / segmental vessels              |
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1. The Avascular Line of Brödel & Target Calyx Selection

• The main renal artery bifurcates into an anterior division (supplying the apical, upper, middle, and lower anterior segments) and a posterior division (supplying the posterior segment).
• The relatively avascular plane of Brödel is a longitudinal watershed zone located approximately 1 to 2 cm posterior to the lateral convex border of the kidney, separating the anterior and posterior arterial territories.
• Puncture Rule: Prefer a posterior calyceal, transpapillary trajectory near this plane. The papilla projects into the calyx; its tip is not the surrounding fornix. Central pelvic or infundibular access risks major vessels, so plan and monitor the actual tract rather than assuming any route is completely avascular.

2. Upper Pole vs. Lower Pole Calyceal Access

• Lower Pole Posterior Calyx: Safest and most common access route. Located subcostally (below the 12th rib), avoiding pleural reflection and thoracic morbidity. Provides excellent access to the renal pelvis, pelviureteric junction, and proximal ureter.
• Upper Pole Calyx: Delivers a direct coaxial trajectory down the long axis of the kidney, allowing thorough inspection of the pelvis and entire ureter. However, upper pole calyces often lie above the 12th rib:
  • Supra-12th Rib (Intercostal) Puncture: Placed between the 11th and 12th ribs. Associated with a 4% to 10% risk of pleural injury (hydrothorax, hemothorax, pneumothorax).
  • Supra-11th Rib Puncture: Placed between the 10th and 11th ribs. Carries a $> 25 - 35\%$ risk of pleural violation and severe lung, splenic, or hepatic laceration. It is strictly avoided unless no alternative exists.
  • Technique: Intercostal punctures must be executed during full expiration along the upper border of the lower rib to avoid the intercostal neurovascular bundle running along the inferior costal groove.

3. Puncture Guidance: Fluoroscopy vs. Ultrasonography

• Fluoroscopy:
  • Bullseye (Eye-of-the-Needle) Technique: The C-arm is aligned with the chosen calyx and needle trajectory. Advance along the aligned trajectory while using an additional oblique or lateral view to monitor depth. Alternate views as needed rather than judging depth from the bullseye projection alone.
  • Triangulation Technique: Use AP and oblique fluoroscopic views to determine direction and depth; adjust C-arm angles to the patient and target calyx.
• Ultrasonography: Real-time 3.5–5.0 MHz convex probe guidance. Allows direct visualization of the renal parenchyma, needle tip trajectory into the targeted papilla, and precise identification of interposed viscera (liver, spleen, retrorenal colon). Significantly reduces or completely eliminates ionizing radiation exposure to the patient and surgical team.

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Tract Dilation: Modalities and Mini-PCNL Dynamics

Once a safety guidewire (0.035-inch or 0.038-inch stiff hydrophilic or Amplatz wire) is secured down the ureter, the percutaneous tract is dilated:

1. Tract Dilation Modalities

• High-Pressure Balloon Dilator: An inflatable balloon catheter (inflated up to 20–30 atmospheres) dilated in a single step over the wire, over which the Amplatz sheath is slid. Provides radial dilation and can shorten access time. Bleeding and access success depend on anatomy, technique and experience; no dilator is universally safest.
• Amplatz Serial Semirigid Dilators: Sequential polyurethane dilators (from 8 to 30 Fr). Exerts both radial and longitudinal shearing forces; carries risk of pushing the guidewire through the medial renal pelvis if excessive axial force is applied.
• Alken Telescoping Metal Dilators: Coaxial rigid metal dilators. Highly effective for traversing dense fibrous scar tissue in previously operated kidneys, but requires careful depth control to avoid pelvic perforation.

2. Standard PCNL vs. Mini-PCNL

Modern endourology stratifies percutaneous access by sheath caliber:

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|                                    STANDARD PCNL vs. MINI-PCNL                                     |
|                                                                                                    |
| STANDARD PCNL                                     MINI-PCNL                                        |
| Sheath size: 24–30 Fr                             Sheath size: 12–20 Fr                            |
| Nephroscope: 20–26 Fr                             Nephroscope: 8–12 Fr                             |
| Ultrasonic, pneumatic or laser energy             Ho:YAG or TFL laser energy                       |
| Forceps extraction and aspiration                 Vacuum-cleaner fluid dynamics                    |
| Commonly large/complex burdens                    Commonly smaller burdens; selected larger cases  |
| Greater blood loss than mini-PCNL                 Lower blood loss than standard PCNL              |
| Drainage: individualized                          Drainage: individualized                         |
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• Mini-PCNL Hydrodynamics ("Vacuum-Cleaner Effect"): In Mini-PCNL, pressurized irrigation creates fluid eddies within the small renal pelvis. By withdrawing the miniaturized scope slightly within the sheath, a pressure differential is established (Bernoulli principle) that draws fragmented stone gravel and dust backwards out of the sheath alongside egressing irrigation fluid.
• Intrarenal Pressure Hazard: A 14 Fr outer diameter has one-fourth the cross-sectional area of a 28 Fr diameter; effective outflow also depends on scope size. In small tracts, restricted outflow can generate dangerously elevated intrarenal pressures ($> 40 - 60$ cmH2O) if pressurized pumping is used without continuous drainage, escalating the risk of pyelovenous backflow and urosepsis.
• Tubeless and Totally Tubeless PCNL:
  • Tubeless PCNL: Omission of an external nephrostomy tube at case conclusion, placing an internal double-J ureteral stent only. Indicated when the case is uncomplicated, stone-free, without significant bleeding or collecting system perforation. Reduces post-operative pain and hospital stay.
  • Totally Tubeless PCNL: Omission of both nephrostomy tube and internal ureteral stent. An option after appropriately selected uncomplicated PCNL, regardless of tract label, when bleeding, obstruction, leakage or a planned second look does not require drainage.

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Major Complications and Emergency Management

1. Severe Vascular Hemorrhage

Severe bleeding is the most frequent major complication of PCNL (transfusion required in 1–5%):

• Intraoperative Venous Hemorrhage: Manifests as dark, non-pulsatile blood obscuring visualization, usually arising from parenchymal venous channels along the dilated tract.
  • Immediate Action: Stop the procedure immediately. Resuscitate and place an appropriately positioned nephrostomy for tamponade and drainage. Briefly clamp it with close monitoring. If a balloon device is used, confirm its position and follow the device technique; do not inflate a balloon blindly in renal tissue.
  • Physiological Mechanism: Clamping increases hydrostatic backpressure within the collecting system and tract, producing local tamponade that may control venous bleeding. Reassess promptly; persistent bleeding or instability needs urgent escalation.
• Delayed Post-Operative Arterial Hemorrhage: Characterized by sudden, massive, pulsatile bright-red bleeding into the nephrostomy bag or severe hematuria, occurring hours to weeks post-operatively (often precipitated by exertion or nephrostomy tube removal).
  • Etiology: Vascular injury creating a pseudoaneurysm or arteriovenous fistula (AVF) (incidence 1–2%), resulting from laceration of an interlobar or segmental artery.
  • Immediate Action: Resuscitate the patient with intravenous fluids and blood products; clamp the nephrostomy tube.
  • Definitive Treatment: Emergent Digital Subtraction Angiography (DSA) followed by superselective Transcatheter Arterial Embolization (TAE) using microcoils, Gelfoam, or liquid embolic agents. Superselective TAE usually controls bleeding while preserving renal tissue; repeat treatment may be needed. Surgical control, including nephrectomy when necessary, is reserved for refractory bleeding or situations where embolization is unavailable or unsuitable.

2. Visceral Injury: Colon Perforation

Colonic perforation occurs in 0.2% to 0.5% of PCNLs, primarily involving the descending colon during left-sided lower pole punctures.

• Anatomical Risk Factors: A retrorenal colon (where the colon lies posterolateral or posterior to the kidney, seen in 1–2% of patients in the supine position and up to 10% in the prone position or in horseshoe kidneys), absent retroperitoneal fat, or extreme lateral punctures.
• Clinical Recognition: Direct endoscopic visualization of colonic haustra or fecal debris; presence of feces or gas in the nephrostomy tube; pneumoperitoneum; or post-operative nephrostogram showing radiocontrast outlining colonic mucosa.
• Management Protocol:
  • Extraperitoneal Colonic Perforation (Most Common): Patient has no signs of peritonitis. Managed non-operatively:
    1. Immediately separate the urinary tract from the gastrointestinal tract.
    2. Place an internal ureteral double-J stent under fluoroscopic guidance to provide low-pressure internal urinary diversion.
    3. Retract the percutaneous nephrostomy tube slightly so that its tip lies entirely within the colon lumen, converting it into a controlled colostomy tube to vent bowel gas and feces.
    4. Administer intravenous broad-spectrum antibiotics covering enteric coliforms and anaerobes, institute bowel rest (NPO) and total parenteral nutrition (TPN).
    5. Coordinate tube withdrawal with urology and colorectal surgery after clinical improvement and contrast confirmation that the urinary-colonic communication has closed; healing often takes about 1–2 weeks.
  • Intraperitoneal Colonic Perforation: The peritoneal cavity is breached, causing acute generalized peritonitis. Requires urgent surgical exploration and source control. Repair or resection, washout and the need for diversion depend on injury extent, contamination and patient stability.

3. Pleural Breach and Thoracic Injury

• Occurs in 4% to 10% of supra-12th rib punctures and $> 25\%$ of supra-11th rib punctures.
• Manifestations: Acute post-operative tachypnea, hypoxia, pleuritic chest pain, diminished breath sounds, or large fluid collections on fluoroscopy/chest radiograph (hydrothorax, hemothorax, pneumothorax).
• Management: Assess breathing, oxygenation and chest imaging promptly. A small stable pneumothorax or hydrothorax may be observed; symptomatic or significant collections need thoracic drainage. Tension physiology requires immediate emergency decompression.

4. Urosepsis and Systemic Inflammatory Response Syndrome (SIRS)

• Raised intrarenal pressure and infected stones can promote backflow and bloodstream infection; pressure, duration, organisms and patient susceptibility all contribute.
• Manifestations: Shivering, hyperthermia or hypothermia, tachycardia, tachypnea, leukocytosis, and sudden hypotension.
• Prevention & Treatment: Obtain preoperative urine culture, treat infection and provide appropriate perioperative prophylaxis; obtain renal pelvic urine and/or stone cultures at PCNL when possible. Limit operative duration and irrigation pressure. For suspected sepsis, stop stone treatment, ensure drainage, take cultures without delaying IV antibiotics, and resuscitate with monitored crystalloids, usually balanced solutions. Choose empiric coverage by severity, prior cultures and local resistance, then narrow to results; critical illness/ESBL risk may require a carbapenem. Septic shock requires critical-care support and norepinephrine when hypotension persists despite appropriate fluids.

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Comparative Reference Tables

Percutaneous Nephrolithotomy Technique & System Comparison

PCNL Patient Positioning Comparison

Major PCNL Complications and Management

Laparoscopic Access and Pneumoperitoneum

Laparoscopic urological surgery adds risks from abdominal entry, carbon-dioxide insufflation and positioning. A Veress needle or trocar can injure bowel or major vessels. Plan access for the patient's anatomy and previous surgery, check the equipment before use, and recognise injury promptly; a small skin incision does not imply a minor internal injury.

Carbon-dioxide absorption can increase arterial CO2 and cause respiratory acidosis. Raised intra-abdominal pressure displaces the diaphragm upwards, reduces respiratory compliance and can increase airway pressures; head-down positioning can worsen these effects. Pneumoperitoneum also changes venous return and systemic vascular resistance and may reduce renal perfusion and urine output.

Coordinate insufflation pressure, positioning and ventilation with the anaesthetist. Monitor oxygenation, end-tidal CO2, airway pressures and haemodynamics. Oliguria during pneumoperitoneum needs clinical assessment; it does not by itself prove dehydration or justify indiscriminate fluid loading.

Worked decision: Immediately after insufflation, profound bradycardia and hypotension develop. Stop insufflation, release pneumoperitoneum and resuscitate with the anaesthetic team while evaluating causes, including a vagal response, haemorrhage and gas embolism. A sudden end-tidal CO2 change with cardiovascular collapse raises concern for gas embolism; provide oxygen and emergency resuscitation. Persistent instability or suspected visceral/vascular injury requires prompt definitive assessment and repair, including conversion to open surgery when needed.

Primary references: EBU ETR, laparoscopic surgery and Society of Laparoscopic & Robotic Surgeons: access and physiological effects.

Rare Open and Laparoscopic Stone Surgery

Open or laparoscopic stone removal remains an option when SWL, retrograde or antegrade ureteroscopy and PCNL have failed or are unlikely to succeed. Review anatomy, previous procedures and local expertise before choosing it. Open surgery is generally a last option; most staghorn stones are approached primarily with PCNL, sometimes combined with RIRS.

Worked decision: A persistent large proximal ureteric stone cannot be cleared despite appropriate endourological attempts. Specialist laparoscopic ureterolithotomy may be reasonable. The existence of this rescue option does not make open surgery first-line for an otherwise straightforward large renal stone.

Primary reference: EAU Urolithiasis, section 3.4.11.