Percutaneous Nephrolithotomy (PCNL) in Urology
Percutaneous nephrolithotomy (PCNL) is a minimally invasive surgical procedure used to remove large kidney stones by creating a small puncture through the skin into the kidney to access and extract stones directly from the collecting system. 1
Definition and Indications
- PCNL is the first-line treatment for renal stones >20mm due to significantly higher stone-free rates (87%) compared to other treatment modalities 1, 2
- For lower pole stones 10-20mm, PCNL offers superior success rates (87%) compared to ureteroscopy (81%) and shock wave lithotripsy (58%) 1, 3
- PCNL is indicated for complex, high-volume, and branched renal stones that are not amenable to other treatment options 3
- PCNL may be considered for stones within complex urinary tracts (urinary diversions, transplanted kidney, horseshoe kidneys) 4
Procedural Technique
- The procedure involves creating percutaneous access to the kidney's collecting system through a small incision in the flank 5
- Both prone and supine positions are acceptable for PCNL, with supine position offering the advantage of simultaneous retrograde access if needed 1
- The procedure typically includes these steps:
- Placement of an open-ended catheter or occlusion balloon into the collecting system via cystoscopy 4
- Percutaneous access to the kidney using an 18G needle under ultrasound or fluoroscopic guidance 1, 4
- Tract dilation to allow insertion of a nephroscope (options include metallic telescopic, single-step, or balloon dilators) 1, 4
- Stone fragmentation using ultrasonic, pneumatic, or laser lithotripsy 1
- Stone fragment removal 5
- Flexible nephroscopy to check for residual fragments 3
Key Technical Considerations
- Normal saline irrigation must be used during PCNL to prevent electrolyte abnormalities that could lead to hemolysis, hyponatremia, and heart failure 3, 1
- Flexible nephroscopy should be a routine part of standard PCNL to access stone fragments that may migrate into areas inaccessible by rigid nephroscope 3, 1
- In uncomplicated PCNL cases, placement of a nephrostomy tube is optional ("tubeless PCNL") 3, 1
- The tubeless approach should not be undertaken if there is active hemorrhage or if another percutaneous procedure will be needed to remove residual stones 3
Contraindications
- Untreated urinary tract infection 1
- Tumor in the access tract 1
- Suspected malignant kidney tumors 1
- Pregnancy 1
- Use of anticoagulation or antiplatelet therapy that cannot be discontinued 3
- Anatomic derangements that may preclude proper positioning 3
Complications and Management
- Common complications include:
- Risk factors for complications include stone burden, operative time, and patient comorbidities 1, 6
- If purulent urine is encountered during the procedure, it should be aborted, appropriate drainage established, antibiotic therapy continued, and a urine culture obtained 3
Recent Advances
- Mini-PCNL uses smaller access sheaths (16.5F) and nephroscopes (12F) to potentially reduce morbidity while maintaining efficacy 4
- Ambulatory PCNL has been shown to be safe and feasible in selected patients when performed by experienced endourologists, with low hospital transfer (2.4%) and readmission rates (4.2%) 7
- Endoscopic combined intrarenal surgery techniques facilitate high stone-free rates with minimal morbidity 7
Clinical Pearls and Pitfalls
- Failure to perform flexible nephroscopy may result in residual stone fragments and future stone events 3, 1
- Using non-isotonic irrigation solutions increases the risk of serious complications 3
- In patients with negligible kidney function in the affected kidney, nephrectomy may be considered instead of PCNL 3, 2
- For patients with obstructing stones and suspected infection, urgent drainage of the collecting system with a stent or nephrostomy tube is mandatory before definitive stone treatment 1, 2