# Percutaneous Nephrostomy

## Overview

Percutaneous nephrostomy (PCN) is the image-guided placement of a drainage catheter into the renal collecting system for urinary diversion. Indicated for obstructive uropathy, pyonephrosis, and urinary diversion in ureteral injury. Performed under ultrasound and fluoroscopic guidance with local anesthesia and sedation. One of the most commonly performed IR procedures.

## Indications

### Emergent

**Pyonephrosis**: infected, obstructed collecting system — urologic emergency. Requires urgent decompression regardless of coagulation status. Delay can result in septic shock and death. **Obstructive uropathy with renal failure**: bilateral obstruction or obstruction of a solitary kidney. **Anuria from bilateral ureteral obstruction**.

### Elective / Semi-Urgent

Malignant ureteral obstruction (cervical, bladder, prostate, colon, retroperitoneal lymphadenopathy). Benign ureteral obstruction (urolithiasis not amenable to retrograde stenting, ureteral stricture, retroperitoneal fibrosis). Urinary diversion for ureteral injury or fistula. Access for antegrade ureteral interventions (stent placement, stone extraction, stricture dilation). Preoperative drainage before definitive urologic surgery. Post-transplant ureteral complications (obstruction, leak).

### Relative Contraindications

Uncorrectable coagulopathy (relative — emergent PCN for pyonephrosis overrides). Non-dilated collecting system (technically more challenging, lower success rate). Hyperkalemia requiring immediate dialysis (PCN alone may not correct rapidly enough). Terminal illness where drainage will not improve quality of life (palliative discussion needed).

## Anatomy

### Renal Collecting System

Calyces (minor → major) → renal pelvis → ureteropelvic junction (UPJ) → ureter. Posterior calyces are the preferred target for PCN access. Brodel's line: relatively avascular plane along the posterolateral aspect of the kidney between anterior and posterior vascular territories. Access through a posterior calyx along Brodel's line minimizes vascular injury.

### Access Planning

| Access Site | Advantages | Disadvantages | Best Indication |
|------------|-----------|---------------|-----------------|
| Lower pole (posterior) | Straight-line to UPJ; low pleural risk | May be limited by retrorenal colon | Routine drainage; future interventions |
| Interpolar (posterior) | Good drainage; moderate safety | Less optimal for ureteral work | Drainage only |
| Upper pole (posterior) | Best angle for ureteral stenting/PCNL | Pleural transgression risk (above 12th rib) | Antegrade stenting, staghorn calculi |

**Ideal calyx**: posterior, lower pole (provides straight-line access to UPJ for future interventions). **Upper pole access**: needed for antegrade ureteral stenting or access to upper ureteral pathology; higher risk of pleural transgression (above 12th rib). **Interpolar access**: acceptable for drainage alone. Avoid puncturing through the renal pelvis (risk of major vascular injury at hilum).

<image>Anatomical diagram of the kidney showing the posterior calyceal access route along Brodel's avascular line for percutaneous nephrostomy with relationship to the 12th rib and pleura</image>

## Technique

### Pre-Procedural Preparation

Review cross-sectional imaging (CT or ultrasound) for: Degree of hydronephrosis. Stone burden and location. Collecting system anatomy (duplicated system, ectopic kidney, horseshoe kidney). Relationship of kidney to pleura, colon, and spleen/liver. Coagulation correction: INR ≤1.5, platelets ≥50,000 (emergent pyonephrosis: proceed regardless). Antibiotics: single-dose prophylaxis for routine PCN; broad-spectrum for pyonephrosis. Position: prone or prone-oblique (preferred) or lateral decubitus.

### Ultrasound-Guided Access

Identify the kidney and dilated collecting system with ultrasound. Select target posterior calyx (lower or middle pole). 21-22 gauge needle advanced under real-time ultrasound guidance into the target calyx. Confirm position by aspirating urine (send for culture). If pyonephrosis: aspirate as much purulent material as possible before injecting contrast.

### Fluoroscopic Guidance and Catheter Placement

Inject dilute contrast to opacify the collecting system (antegrade pyelogram). Advance 0.018" wire through needle into collecting system (preferably into ureter or renal pelvis). Transition to 0.035" system via coaxial dilators or AccuStick system. Serial dilation of the tract. Place 8-10 Fr locking pigtail nephrostomy catheter. Lock pigtail in renal pelvis; ensure side holes within collecting system. Secure catheter to skin; connect to drainage bag. Post-procedure fluoroscopy or ultrasound to confirm position.

### Non-Dilated System Access

Significantly more challenging (small target). Opacify the collecting system first: IV contrast and diuretic (furosemide) to distend the system. Retrograde ureteral catheter injection (if cystoscopy available). C-arm CT or cone-beam CT for 3D needle guidance. 22-gauge Chiba needle with multiple passes may be required. Success rate: 85-90% for dilated systems; 70-80% for non-dilated.

<image>Fluoroscopic antegrade nephrostogram showing a dilated collecting system with a pigtail nephrostomy catheter coiled in the renal pelvis and contrast opacifying the proximal ureter down to the level of obstruction</image>

## Post-Procedural Management

### Immediate Care

Monitor urine output from nephrostomy (high output initially if obstructed — post-obstructive diuresis). Post-obstructive diuresis: >200 mL/hour for >2 hours. Replace fluid losses with 0.45% saline at 50-75% of urine output. Monitor electrolytes (potassium, sodium, magnesium). Typically self-limited within 24-48 hours. Monitor for hematuria (common, usually self-limited). Continue antibiotics if pyonephrosis; tailor to culture results.

### Catheter Maintenance

Flush with 5-10 mL saline daily. Monitor output (decrease suggests catheter malposition, kinking, or obstruction). Catheter exchanges every 2-3 months to prevent encrustation. Gravity drainage preferred; no suction.

### Subsequent Interventions

Antegrade ureteral stent placement (convert to internal drainage). Stone extraction via percutaneous nephrolithotomy (PCNL). Ureteral stricture dilation/stenting. Nephroureteral stent placement (internal/external).

## Complications

### Common (Minor)

Transient hematuria (nearly universal, resolves in 24-48 hours). Access site pain. Catheter dislodgement (most common long-term complication).

### Uncommon (Major)

Significant hemorrhage requiring transfusion (1-4%). Arteriovenous fistula or pseudoaneurysm from parenchymal vessel injury. Managed with selective renal artery embolization. Sepsis (2-10%, higher with pyonephrosis). Pleural injury (pneumothorax, hydrothorax) — upper pole access above 12th rib. Colonic injury (rare, retrorenal colon present in 1-10% of patients; check CT before procedure). Urinoma from collecting system leak around catheter. Loss of access (catheter falls out before tract matures — wait ≥5-7 days before removing).

## Clinical Pearls

Pyonephrosis is a true emergency — do not delay PCN for coagulation correction; the risk of untreated sepsis far outweighs bleeding risk. In pyonephrosis, minimize contrast injection — an infected, pressurized system can cause fatal bacteremia; aspirate first, then inject minimal contrast. Always target a posterior calyx (not the renal pelvis) — direct puncture of the renal pelvis risks injury to the hilar vessels and provides poor catheter stability. Lower pole access is ideal for routine drainage; upper pole access is needed if planning antegrade ureteral stenting or PCNL for staghorn calculi. Check for retrorenal colon on pre-procedural CT — the colon can lie posterior to the lower pole in up to 10% of patients (especially on the left). Post-obstructive diuresis can be life-threatening if not managed with appropriate fluid replacement — monitor electrolytes closely in the first 24-48 hours. If the nephrostomy tube dislodges within the first week (before tract maturation), the tract will collapse and a new access must be obtained — secure the catheter well and educate the patient. For malignant obstruction with bilateral hydronephrosis, consider draining the kidney with better function or the more recently obstructed kidney first.

<image>CT image showing retrorenal colon posterior to the left kidney, illustrating the importance of pre-procedural imaging to plan a safe access route for percutaneous nephrostomy</image>

## References
- Ramchandani P, et al. Quality Improvement Guidelines for Percutaneous Nephrostomy. J Vasc Interv Radiol. 2016;27(3):410-414.
- Wah TM, et al. Percutaneous Nephrostomy: Technical Aspects and Indications. Semin Intervent Radiol. 2011;28(4):424-437.
- Zagoria RJ. Percutaneous Nephrostomy and Ureteral Stenting. In: Genitourinary Radiology. Elsevier; 2016.
- Saad WE, et al. ACR/SIR Practice Parameter for Percutaneous Nephrostomy. J Vasc Interv Radiol. 2016;27(3):410-414.
- Millward SF. Percutaneous Nephrostomy: A Practical Approach. J Vasc Interv Radiol. 2000;11(8):955-964.