Is an infected stone a contraindication to lithotripsy?

Infected Stones Are a Contraindication to Lithotripsy

In patients with obstructing stones and suspected infection, the collecting system must be urgently drained with a stent or nephrostomy tube and stone treatment should be delayed until the infection is resolved. 1

Understanding the Risk

When infection is present with an obstructing stone, immediate lithotripsy poses significant risks:

• Bacteremia and sepsis can occur when infected urine under pressure is forced into the bloodstream during lithotripsy
• Manipulation of infected stones can release bacteria and endotoxins
• The risk of periprocedural infectious complications is considerable in contaminated cases 1

Management Algorithm for Infected Stones

1. Initial Presentation with Suspected Infected Stone:

   • Obtain urine microscopy and culture
   • Assess for signs of systemic infection (fever, leukocytosis)
   • Evaluate for obstruction on imaging

2. If Infection + Obstruction Present:

   • Urgent decompression required via:
     • Nephrostomy tube placement OR
     • Retrograde ureteral stent placement 1
   • Start appropriate antibiotics based on local antibiogram or previous cultures

3. Delay Definitive Stone Treatment:

   • Complete antibiotic course
   • Wait for resolution of infection symptoms
   • Confirm negative urine cultures before proceeding 1

4. Once Infection Resolved:

   • Proceed with appropriate stone treatment based on size and location
   • For stones <20mm: SWL or URS may be considered
   • For stones >20mm: PCNL is preferred 1

Evidence Supporting This Approach

The 2016 AUA/Endourological Society guidelines explicitly state that when infection is suspected with ureteral obstruction, "the collecting system must be drained either by a nephrostomy tube or a ureteral stent, to allow drainage of infected urine and antibiotic penetration into the affected renal unit" 1.

The 2020 Best Practice Statement on Urologic Procedures and Antimicrobial Prophylaxis emphasizes that "elective procedures should be deferred in the presence of symptoms consistent with an active infection until an antimicrobial course is complete and associated symptoms have improved" 1.

Special Considerations

• Stone Culture: Recent research shows patients with positive stone cultures have significantly higher rates of major infectious complications (15.6% vs 0.4%) after ureteroscopic lithotripsy 2
• Risk Factors for Infected Stones: Diabetes, recent urinary infections, and preoperative stents/nephrostomies increase the likelihood of positive stone cultures 2
• Residual Fragments: Infected stone fragments left after treatment have a high rate of progression (78%) and should be completely removed 3

Pitfalls to Avoid

1. Don't perform immediate lithotripsy on infected stones - this can lead to life-threatening sepsis
2. Don't rely solely on urine cultures - stone cultures may contain different pathogens than urine 2
3. Don't underestimate infection stones - they require complete removal to prevent recurrence and ongoing infection 1
4. Don't delay drainage when infection and obstruction coexist - this is a urologic emergency requiring prompt intervention

By following this approach of drainage first, followed by definitive treatment only after resolution of infection, you can significantly reduce the risk of serious infectious complications and improve patient outcomes.