Acetic Acid Flush for Urinary Catheters
Acetic acid flush should NOT be used routinely for catheter irrigation to prevent catheter-associated bacteriuria or UTI, as it has been proven ineffective in randomized trials and is explicitly recommended against by IDSA guidelines. 1
Evidence-Based Recommendations
Routine Prevention: Not Indicated
The 2009 IDSA guidelines provide clear, high-quality evidence (A-I and A-II ratings) that catheter irrigation with antimicrobials—including acetic acid—should not be used routinely to reduce or eradicate catheter-associated bacteriuria or catheter-associated UTI in patients with indwelling catheters 1. This recommendation is based on multiple randomized controlled trials showing no benefit.
Why Acetic Acid Fails
The evidence demonstrates two critical failures of acetic acid irrigation:
No effect on bacterial counts: A 1978 randomized trial found that 0.25% acetic acid irrigation had no effect on urinary bacterial counts in catheterized patients with pre-existing UTI 2
Cannot prevent encrustation: In vitro experiments conclusively showed that acidification of urine is not feasible for preventing catheter encrustation. When urease-producing bacteria are present, they continuously convert urea to ammonia, rapidly neutralizing any acidification attempt 3
Ineffective in neurogenic bladder patients: A randomized double-blind study of 89 community-dwelling patients with neurogenic bladders showed no effect on bacteriuria levels from twice-daily bladder irrigation with acetic acid versus sterile saline 1
The Only Historical Exception (No Longer Relevant)
Acetic acid has been mentioned in older literature (1969-1975) for two very specific, limited uses 4, 5:
- Candida bladder infections: Continuous irrigation with increasing concentrations up to pH 5.0 was used for fungal infections, not bacterial prevention
- Dissolving calcium deposits: Used therapeutically to dissolve existing encrustations, not prophylactically
These are therapeutic interventions for established problems, not preventive measures.
What Actually Works
For Catheter Blockage Prevention
Replace the catheter rather than attempting irrigation. The IDSA guidelines note that patients with repeated early catheter blockage from encrustation are sometimes managed with catheter changes every 7-10 days, though this lacks trial evidence 1. Irrigation with normal saline should not be used routinely for obstruction prevention in long-term catheterization (B-II recommendation) 1.
For Infection Prevention
The 2025 ISID guidelines reinforce that catheter irrigation as a preventive measure against infection is not advisable 6. Instead, focus on:
- Early catheter removal when no longer indicated
- Maintaining closed drainage systems
- Proper insertion technique
- Routine hygiene (not antiseptic meatal cleansing)
Common Pitfalls to Avoid
Do not confuse therapeutic dissolution with prevention: While acetic acid may dissolve existing calcium deposits, it does not prevent new encrustation or infection 3, 5
Do not use any routine bladder irrigation for infection prevention: This includes saline, acetic acid, chlorhexidine, or other antimicrobials in standard catheter care 1
Do not attempt to acidify urine in urease-producing infections: The bacteria will simply produce more ammonia, neutralizing your efforts and making the intervention futile 3
The Bottom Line
Recent systematic review data (2026) examining prophylactic catheter washouts found only low to very low certainty evidence for any benefit, with acidic washouts showing minimal advantage over saline or no washout 7. The evidence consistently demonstrates that acetic acid flush has no role in routine catheter management for infection or blockage prevention.