What is a PCNU?
A PCNU (Percutaneous Nephroureteral) catheter is a specialized urinary drainage tube that is inserted through the skin into the kidney and extends down through the ureter, providing continuous drainage from the kidney to the bladder or externally. 1, 2
Technical Details and Placement
A PCNU catheter differs from a standard percutaneous nephrostomy (PCN) tube in the following ways:
- Placement path: While a PCN tube is inserted into the kidney and terminates in the renal collecting system, a PCNU extends further down through the ureter
- Design: PCNU catheters are typically longer and may have specialized features to maintain position across the ureter
- Drainage pattern: PCNUs allow for antegrade drainage from kidney through ureter, potentially restoring more physiologic urinary flow
The placement procedure typically involves:
- Initial percutaneous access to the kidney under ultrasound guidance
- Advancement of the catheter through the renal collecting system and down the ureter under fluoroscopic guidance
- Positioning with drainage holes in both the kidney and along the ureter 1
Clinical Indications
PCNU catheters are indicated in several clinical scenarios:
- Ureteral obstruction or strictures: When retrograde access fails or is contraindicated
- Urinary diversion after cystectomy: Especially when there is hydronephrosis and no reflux into distal ureters 1
- Ureteral leaks or injuries: To bypass the damaged segment and restore continuity 1
- Intractable hematuria: PCNUs have been shown to effectively manage refractory gross hematuria by diverting urine and preventing clot formation 3
Advantages Over Other Drainage Options
PCNUs offer several advantages in specific clinical scenarios:
- Preferred over internal double-J stents in ileal conduits: Double-J stents tend to occlude quickly due to mucous plugging within ileal conduits, while PCNUs maintain patency better 1
- Better tolerance than external PCN tubes: While PCNUs may exit the skin, they can provide more physiologic drainage than PCN tubes alone
- High technical success rate: Technical success approaches 100% when performed with image guidance 2
- Effective management of hematuria: PCNUs are less likely to become obstructed by blood clots compared to other drainage options 3
Complications and Considerations
Common complications associated with PCNU placement include:
- Bleeding: Mild hematuria occurs in approximately 50% of patients after placement, though clinically significant bleeding is less common 1, 2
- Infection/sepsis: Particularly in patients with pre-existing infection or diabetes 2
- Catheter displacement: Reported in up to 12.6% of cases 2
- Catheter blockage: Occurs in approximately 3.3% of cases 2
Less common but serious complications include:
- Bowel injury
- Splenic injury
- Pneumothorax (more common with upper-pole calyceal puncture)
- Vascular injuries requiring embolization 1
Monitoring and Management
For patients with PCNU catheters:
- Regular monitoring for signs of infection or obstruction
- Catheter changes typically every 4-12 weeks
- Monitoring for improvement in clinical parameters (resolution of pain, normalization of vital signs)
- Evaluation for definitive treatment of the underlying condition 2
PCNU catheters represent an important tool in the interventional management of urinary tract obstruction, providing effective drainage while potentially allowing for more definitive treatment of the underlying condition.