How to manage and prevent encrustation in a urinary Foley (Foley catheter) catheter?

Management and Prevention of Foley Catheter Encrustation

The most effective strategy to prevent catheter encrustation is early removal of the catheter as soon as medically feasible, as catheter duration is the primary risk factor for crystalline biofilm formation and blockage. 1, 2

Understanding the Problem

Catheter encrustation occurs when urease-producing bacteria, particularly Proteus mirabilis, colonize the catheter and form crystalline biofilms. 1, 3 These organisms generate ammonia from urea, elevating urinary pH above 7.0, which causes calcium and magnesium phosphate crystals to precipitate within the catheter lumen and biofilm. 3, 4 In a study of 1,135 weekly urine specimens from 32 long-term catheterized patients, 86% had urease-positive bacteria, and P. mirabilis was significantly associated with 67 catheter obstructions observed. 1

Blocked catheters can lead to serious complications including urinary retention, bladder distension, pyelonephritis, septicemia, and endotoxic shock if not promptly identified and changed. 3

Primary Prevention Strategies

Catheter Removal and Alternatives

• Reassess catheter necessity daily and remove within 48 hours when possible, as infection risk increases exponentially with prolonged catheterization. 2
• Consider intermittent catheterization instead of indwelling catheters when feasible, as this significantly reduces infection and encrustation risk. 2
• Maintain a closed drainage system at all times with the collection bag positioned below bladder level to prevent retrograde bacterial migration. 2

Catheter Selection

• Use silver alloy-coated urinary catheters rather than standard catheters, as meta-analyses demonstrate they significantly reduce UTI rates despite higher upfront costs. 2
• Note that all types of Foley catheters, including silver- or nitrofurazone-coated devices, remain vulnerable to encrustation by P. mirabilis biofilms. 3

Management of Established Encrustation

For Patients with Recurrent Blockage

• Replace the catheter immediately when blockage occurs or is imminent, as biofilms on existing catheters harbor bacteria protected from antimicrobials. 2
• There is insufficient evidence to recommend routine scheduled catheter changes (e.g., every 2-4 weeks) to prevent encrustation, even in patients experiencing repeated early blockage. 1
• For chronic blockers, some experts suggest catheter changes every 7-10 days to avoid obstruction, though this has not been evaluated in clinical trials. 1

Fluid and Dietary Management

• Increase fluid intake with citrated drinks to dilute urine and potentially reduce crystal formation, particularly for patients who are already chronic blockers and stone formers. 4

What NOT to Do

Ineffective Interventions

• Do not use routine bladder irrigation with normal saline or antiseptics to prevent encrustation, as randomized trials in long-term catheterized patients showed no reduction in catheter obstructions or febrile episodes. 1
• Do not routinely add antimicrobials or antiseptics to the drainage bag, as this does not reduce catheter-associated bacteriuria or UTI (A-I level evidence). 1
• Do not use prophylactic systemic antimicrobials routinely at catheter placement, removal, or replacement, as this increases antimicrobial resistance without proven benefit (A-I level evidence). 1, 2
• Do not routinely change catheters as a preventive measure against infection. 1

Treatment of Underlying Infection

When P. mirabilis is Identified

• Eliminate P. mirabilis with antibiotic therapy as soon as it appears in the catheterized urinary tract, before bladder stones develop and biofilms become established. 4
• Obtain urine culture before initiating treatment to guide antimicrobial selection. 2
• Replace the catheter before treating symptomatic UTI, as biofilms on the existing catheter protect bacteria from antimicrobials. 2

For Chronic Stone Formers

• Antibiotic treatment is unlikely to be effective once P. mirabilis establishes stable residence in bladder stones due to resistance of cells in crystalline biofilms. 4
• Surgical removal of bladder stones should be organized for these patients. 4

Emerging Strategies (Not Yet Standard Practice)

Urease Inhibition

• Acetohydroxamic acid (AHA) reversibly inhibits bacterial urease, reducing ammonia production and urinary pH elevation. 5
• AHA has shown benefit in reducing stone growth rates in patients not candidates for surgical stone removal and may allow successful antibiotic treatment after stone removal. 5
• 36-65% of oral AHA is excreted unchanged in urine, where concentrations as low as 8 mcg/mL may inhibit urease. 5

Novel Catheter Technologies

• Experimental catheters with triclosan-impregnated retention balloons completely inhibited crystalline biofilm formation for at least 7 days in laboratory models, while control catheters blocked within 24 hours. 6
• Double-balloon catheters capable of periurethral irrigation with antimicrobial solutions showed significant inhibition of biofilm colonization in vitro models. 7

Critical Pitfall

The most common mistake is allowing catheters to remain in place longer than medically necessary. Daily assessment and prompt removal when indications no longer exist is the single most effective prevention strategy, as established biofilms are extremely difficult to eradicate once formed. 2, 3