Catheter-associated urinary tract infection

• UTI that occurs in patients with indwelling urinary catheters, or who have had them recently removed.
• Usually presents with non-specific signs and symptoms, so can be difficult to diagnose.

Urine culture results from people who have an existing catheter are almost impossible to interpret because you cannot differentiate between catheter colonisation (essentially universal), asymptomatic bacteriuria, and UTI.

• Test for CAUTI in catheterised patients with clinical features suggestive of UTI without an obvious alternate cause.
  • These features are often non-specific e.g. fever, generally unwell.

• Patients with existing catheters will commonly have cloudy, smelly, or sedimented urine, or a positive dipstick for leucocytes or nitrites.
  • None of these are diagnostic of UTI or a reason to send urine for culture in themselves – the patient must have clinical features that raise suspicion of infection.
  • However, a negative dipstick for leucocytes and nitrites does mean CAUTI is unlikely.

Urine sample for culture – either MSU or from freshly replaced catheter

• Because urine cultures from existing catheters are so difficult to interpret, if CAUTI is suspected it is recommended to remove catheter colonisation from the equation. Either:
  • Remove catheter and obtain MSU sample, or;
  • Replace catheter (usually part of CAUTI management anyway) and obtain urine from freshly inserted catheter
    • It is important to state on the lab request form if urine has been obtained from a fresh catheter, as the lab will treat this differently.

• If the patient is systemically unwell then 2 sets of blood cultures should also be collected.

Sending urine for culture in patients without clinical features of infection

• This is a common cause of unnecessary antibiotic treatment.
• This includes cloudy, smelly, or sedimented urine without other features.
• This includes positive dipstick for leucocytes or nitrites without other features.