Catheter-associated urinary infection

01OverviewDefinition, clinical context and the essential points that orientate the chapter.

Catheter-associated urinary tract infection is symptomatic infection in a person with a current catheter or within 48 hours of removal. Biofilm and bacteriuria are expected with prolonged catheterisation, so culture alone has poor specificity.

The first questions are whether symptoms are attributable to the urinary tract, whether the catheter is still needed and whether urine drains freely. Mechanical blockage can cause pain, leakage and renal injury without invasive infection.

Fresh urine from a disinfected sampling port or a newly replaced catheter better represents bladder organisms than stagnant drainage-bag urine. Treatment then follows lower-tract, upper-tract or sepsis localisation.

Delirium or functional decline must be assessed broadly. A chronically colonised catheter provides an attractive but often false explanation, so seek medication effects, dehydration, constipation, hypoxia, metabolic disturbance and infection at another site before assigning causation.

Key points

Bacteriuria becomes common with catheter duration and does not by itself diagnose catheter-associated urinary infection.
Require compatible urinary or systemic symptoms and actively assess catheter blockage, trauma, bladder spasm and non-urinary causes.
Do not use urine dipsticks to diagnose infection in catheterised adults because leucocytes, blood and nitrite are frequently misleading.
Obtain urine before antibiotics from the sampling port using aseptic technique, or from a newly inserted catheter after change; never use the drainage bag.
Remove the catheter when no longer needed; if it has been in place more than seven days and remains necessary, change it promptly without delaying antibiotics.
Lower-tract symptoms may use a seven-day oral regimen; upper-tract or septic features require pyelonephritis or sepsis treatment.
Do not give routine antibiotic prophylaxis to prevent infection during long-term catheter use or every catheter change.
Review culture and response within 48 hours and investigate ongoing obstruction, encrustation, stones or an alternative source.

02AetiologyUnderlying causes, associations and risk factors, with why each one matters.

Ascending catheter biofilm

Organisms introduced during insertion or through the drainage system adhere to catheter surfaces and ascend within structured microbial biofilm.

Enteric and healthcare organisms

Escherichia coli, Klebsiella, Proteus, Pseudomonas, enterococci and Candida become more likely with duration, healthcare exposure and previous antibiotics.

Mechanical predisposition

Obstruction, encrustation, dependent-loop failure, disconnection and mucosal trauma impair bladder drainage and increase symptomatic infection risk.

03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.

1
Biofilm persistence
Extracellular biofilm protects organisms from host defence and antimicrobials, making bacteriuria progressively common while the device remains.
2
Mucosal injury and ascent
Catheter friction disrupts urothelium, while a bypassed urethral barrier permits organisms to reach bladder and potentially upper tracts.
3
Obstruction and pressure
Encrustation or kinking produces urinary retention, reflux and renal pressure, which can amplify infection and acute kidney injury.
4
Bloodstream invasion
Upper-tract spread or traumatic manipulation during heavy colonisation can seed blood and cause sepsis in vulnerable patients.

04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.

Attributable urinary symptoms

New suprapubic pain, flank pain, acute haematuria, pelvic discomfort or systemic fever and rigors support infection when another cause is not better.

Mechanical catheter problemRed flag

Bypassing, poor drainage, sediment, bladder distension, pain or spasm suggests kinking, encrustation, displacement or blockage needing immediate correction.

Upper-tract progressionRed flag

Loin pain, fever, rigors, vomiting or renal tenderness should be managed as catheter-associated pyelonephritis rather than lower infection.

Sepsis presentationRed flag

Hypotension, confusion, tachypnoea, mottling or reduced urine output demands urgent systemic treatment while other sources are considered.

Colonisation without infection

Cloudy or malodorous urine and a positive culture are common during catheterisation and do not justify antibiotics without compatible symptoms.

Red flags requiring action

Absent catheter drainage with a painful palpable bladder suggests acute retention or mechanical obstruction.
Fever, rigors, loin pain or costovertebral-angle tenderness indicates possible upper urinary tract involvement.
Hypotension, tachypnoea, confusion, mottling or oliguria requires urgent sepsis assessment.
Visible haematuria with clots can obstruct the catheter and requires urgent urological assessment.
Persistent symptoms after catheter change and active therapy suggests stone, abscess, resistant infection or another source.

05InvestigationsWhat to request, why it matters and how to interpret it.

Investigation order

Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.

01
Catheter system examinationFirst step
Why
Identify kinking, disconnection, leakage, bladder distension or blockage before attributing poor drainage to infection.
Interpretation and limitations
Restore a closed dependent system and replace a blocked or unnecessary catheter using aseptic technique; document residual volume and urine appearance.
02
Urine culture from sampling port
Why
Obtain a representative pre-treatment sample for organism identification and susceptibility.
Interpretation and limitations
Disinfect the port and aspirate aseptically. If changing the catheter, sample the new device; never submit stagnant drainage-bag urine.
03
Blood cultures
Why
Detect bacteraemia when fever, rigors, hypotension or other systemic features are present.
Interpretation and limitations
Take before antibiotics if this causes no delay. Concordant blood and urine isolates support urinary source attribution.
04
Renal and inflammatory blood tests
Why
Assess acute kidney injury, dosing safety and severity.
Interpretation and limitations
Creatinine may rise from sepsis, dehydration or obstruction. Inflammatory markers cannot distinguish bacteriuria from symptomatic infection.
05
Bladder scan and renal imaging
Why
Assess retention, hydronephrosis, stones or abscess when drainage is poor or response is inadequate.
Interpretation and limitations
A low bag output may reflect dehydration or blockage; urgency rises with anuria, flank pain, renal deterioration or sepsis.

06Differential diagnosisRealistic alternatives and the features that help distinguish them.

Asymptomatic bacteriuria

A positive culture without attributable urinary or systemic symptoms is expected during prolonged catheterisation and does not require routine treatment.

Mechanical blockage or spasm

Poor drainage, pain and bypassing can result from kinking, constipation, encrustation, malposition or bladder spasm without infection.

Non-urinary infection

Pneumonia, skin infection, abdominal disease and line infection can cause fever or delirium while catheter urine is incidentally positive.

Trauma or malignancy

Haematuria can follow insertion trauma, anticoagulation, stones or urinary cancer and requires assessment beyond an infection label.

07ManagementImmediate care, first-line treatment, alternatives and escalation.

01VERIFYConfirm a symptomatic syndromeFirst stepA catheterised adult has cloudy urine, a positive test, pain, fever or functional deterioration.

1Assess for new urinary symptoms, upper-tract signs and sepsis while seeking respiratory, skin, abdominal, neurological and medicine-related alternatives.
2Inspect the catheter and bladder, restore drainage and remove the device if its indication has ended.
3Do not use dipstick or isolated culture to diagnose infection; obtain a fresh culture only when symptoms make treatment plausible.
4Give observation without antibiotics for asymptomatic bacteriuria unless pregnancy or a specified urological-procedure indication applies.

02SAMPLE AND CHANGEImprove drainage and microbiologySymptomatic catheter-associated infection is suspected and the catheter remains required.

1Take urine from the disinfected sampling port before antibiotics, or change the catheter first and sample through the new system.
2If present more than seven days, remove or change the catheter promptly without allowing the procedure to delay antimicrobial treatment.
3Record indication, insertion and change dates, catheter type, residual urine, trauma and whether blockage or encrustation was present.
4Maintain a closed drainage system with the bag below bladder level and minimise future manipulation.

03TREATMatch treatment to localisationCompatible symptoms support lower or upper catheter-associated urinary infection after assessment.

1For lower-tract disease without fever or flank pain, select a seven-day NICE regimen using renal function, culture and susceptibility.
2For upper-tract or septic disease, use the acute pyelonephritis and sepsis pathway with intravenous therapy and imaging when indicated.
3Review culture at 48 hours and narrow, change or stop therapy according to symptoms and susceptibility rather than trying to sterilise chronic catheter urine.
4Investigate recurrence for stones, obstruction, encrustation, fistula or poor catheter indication and seek continence or urology support.

04REASSESSResolve treatment failureSymptoms worsen or fail to improve within 48 hours after catheter and antimicrobial management.

1Repeat observations, bladder examination and drainage assessment and search for a non-urinary infection source.
2Review culture activity, renal function and adherence and change treatment only with a clear clinical reason.
3Arrange imaging and urology input for anuria, hydronephrosis, stones, abscess, persistent haematuria or sepsis.
4DefinitiveDocument catheter need, definitive drainage plan and safety-net instructions before discharge.

Key medicines and prescribing safety4 treatments · regimens, roles and cautions

Treats susceptible lower urinary infection in a catheterised adult without systemic or renal features.

Nitrofurantoin modified release

Give 100 mg orally twice daily for seven days for lower catheter-associated UTI when eGFR is adequate and upper-tract or prostate involvement is excluded.

Usually require eGFR at least 45 mL/minute; do not use for pyelonephritis, sepsis or prostatitis, and review pulmonary, hepatic, neurological and haemolysis risks.

Provides an oral lower-tract option where the organism is likely or proven susceptible.

Trimethoprim

Give 200 mg orally twice daily for seven days for lower catheter-associated UTI when resistance risk is low or susceptibility is known.

Review renal function, potassium, pregnancy relevance and interactions with methotrexate, warfarin, ACE inhibitors and spironolactone; recent use increases resistance risk.

Offers a narrower beta-lactam option for selected culture-confirmed lower catheter-associated infection.

Amoxicillin

Give 500 mg orally three times daily for seven days only when urine culture confirms that the organism is susceptible.

Do not use empirically because resistance is common; clarify penicillin allergy, adjust for renal impairment and review rash, diarrhoea and Clostridioides difficile risk.

Provides tissue-active oral beta-lactam treatment for selected catheter-associated pyelonephritis rather than bladder colonisation.

Cefalexin for upper features

Give 500 mg orally twice or three times daily for seven to ten days when upper-tract infection is stable and guidance supports oral treatment.

Clarify beta-lactam allergy, adjust for renal impairment, use susceptibility and admit for vomiting, sepsis, obstruction or inability to absorb oral medicine.

08ComplicationsImportant consequences, why they occur and why they matter clinically.

Pyelonephritis and urosepsis

Ascending infection reaches renal tissue and blood, producing flank pain, organ dysfunction and shock, particularly with impaired drainage.

Obstructive renal injury

Catheter blockage or encrustation causes urinary retention, hydronephrosis and acute kidney injury even without clinically invasive infection.

Bladder and urethral injury

Traction, false passage, erosion and chronic inflammation cause bleeding, pain, urethral stricture and long-term continence problems.

Antimicrobial resistance

Repeated treatment of colonisation selects multidrug-resistant biofilm organisms and increases drug toxicity and Clostridioides difficile risk.

09Monitoring and follow-upTreatment response, safety checks and longer-term review.

Check that urine flows freely after intervention and record output, bladder symptoms, bypassing and haematuria.
Review observations and mental state frequently when systemic illness is possible; deterioration requires sepsis escalation.
Check culture and susceptibility within 48 hours and document final indication, agent, duration and stop date.
Repeat renal function when acute kidney injury, obstruction or renally cleared antimicrobials are relevant.
Review the ongoing catheter indication and arrange trial without catheter, intermittent catheterisation or specialist planning when feasible.

10Special situationsVariants, exceptions and circumstances that change the usual approach.

Biofilm is expected

Long-term catheters develop polymicrobial biofilm, so attempts to maintain sterile urine with antibiotics are ineffective and harmful.

The bag is not a specimen

Stagnant drainage-bag urine overrepresents colonising organisms and contamination; a fresh sampling-port or new-catheter specimen is required.

Change helps but must not delay

Replacing a longstanding catheter improves drainage and sample relevance, yet sepsis treatment should begin promptly when indicated.

Bypassing is often mechanical

Leakage around a catheter may reflect blockage, constipation, spasm or an incorrect device rather than infection.

Duration follows anatomy

Seven-day lower-tract treatment cannot be copied into sepsis, renal infection or prostate involvement, which follow different guidance.

Catheter necessity is prevention

Daily review and prompt removal reduce future infection risk more effectively than routine cultures, prophylactic antibiotics or frequent unindicated catheter changes.

11Common pitfallsFrequent interpretation and management errors.

01
Do not send routine cultures or prescribe antibiotics for cloudy urine in an otherwise well catheterised adult.
02
Do not collect a diagnostic urine specimen from the drainage bag.
03
Do not use dipstick leucocytes or nitrite to diagnose catheter-associated urinary infection.
04
Do not change a catheter and forget to review whether it remains clinically required.
05
Do not treat systemic catheter-associated infection with nitrofurantoin because tissue and bloodstream exposure is inadequate.