How do we determine if a percutaneous nephrostomy (PN) drain is functioning properly?

Assessing Percutaneous Nephrostomy Drain Function

A properly functioning percutaneous nephrostomy (PCN) drain is primarily determined by adequate urine output, improvement in clinical symptoms, and resolution of laboratory abnormalities that prompted the placement. 1, 2

Primary Indicators of PCN Function

• Urine Output Assessment:

  • Consistent drainage output (typically 30-50 mL/hr or 1-2 mL/kg/hr)
  • Clear or appropriately colored urine (may be initially bloody but should clear)
  • No significant decrease in output over time

• Clinical Improvement:

  • Resolution of flank pain and tenderness
  • Normalization of vital signs (particularly in cases of infection/sepsis)
  • Improvement in patient's overall condition
  • Decreased C-reactive protein levels (a useful, objective parameter for monitoring improvement) 1

• Laboratory Parameters:

  • Improving or normalized renal function tests (creatinine, BUN)
  • Resolution of leukocytosis in cases of infection
  • Negative urine cultures after appropriate antibiotic therapy in cases of infection

Technical Assessment Methods

• Direct Visualization:

  • Inspect the catheter for patency and position
  • Check for kinks, blockage, or displacement
  • Evaluate the insertion site for signs of infection or leakage

• Radiologic Evaluation:

  • Nephrostogram: inject contrast through the PCN to assess for:
    • Proper catheter position within collecting system
    • Free flow of contrast into the ureter (if no distal obstruction)
    • Absence of extravasation
  • Ultrasound: to assess for persistent hydronephrosis

• Drainage Fluid Analysis:

  • In suspected urinary leaks, compare drain fluid creatinine to serum creatinine
  • Drain fluid creatinine level just 18% higher than serum creatinine can indicate a urine leak 1

Common Problems and Solutions

• Decreased Output:

  • Check for catheter obstruction (blood clots, debris, encrustation)
  • Flush gently with sterile saline if obstruction suspected
  • Assess for catheter displacement or kinking
  • Consider catheter exchange if persistently malfunctioning

• Persistent Hydronephrosis:

  • Evaluate catheter position
  • Check for obstruction within the catheter
  • Consider upsizing the catheter if output is inadequate

• Signs of Infection:

  • Fever, increasing WBC, purulent drainage
  • Obtain cultures from the nephrostomy tube
  • Initiate appropriate antibiotic therapy
  • Consider catheter exchange if biofilm formation suspected

Long-term Monitoring

• Regular catheter changes (typically every 4-12 weeks)
• Monitoring for signs of infection or obstruction
• Evaluation for conversion to internal stent if long-term drainage required 2

Pitfalls to Avoid

• Failure to recognize catheter dislodgement: The most common complication (12.6% of cases) 2
• Overlooking catheter blockage: Occurs in approximately 3.3% of cases 2
• Ignoring signs of sepsis: Postprocedural bacteremia and sepsis are common when infected urinary tracts are drained 1
• Inadequate flushing protocol: Regular flushing prevents encrustation and blockage
• Delayed recognition of complications: Bleeding, infection, or catheter malposition require prompt intervention

Remember that a properly functioning PCN should lead to marked clinical and analytical improvement in patients with complicated urinary obstruction 3. The absence of such improvement should prompt immediate reassessment of catheter function and position.