CONTENTS

• Is CAUTI real?
• Diagnostic approach to CAUTI
  • [1] When to suspect CAUTI?
  • [2] Evaluate Foley catheter functionality.
  • [3] Replace Foley & check UA/Cx.
  • [4] Evaluate urinalysis & culture data.
  • Other studies/tests that may occasionally be useful.
• Treatment of CAUTI
  • When to start antibiotics.
  • Antibiotic selection.
  • Duration of antibiotics.
• Prevention
• Related: Candiduria ➡️
• Podcast
• Questions & discussion
• Pitfalls

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is CAUTI real?

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some general principles

• Urinary tract infections may be divided into infections limited to the bladder and urethra (cystitis) and infections which ascend to involve the kidneys (pyelonephritis).
  • Cystitis may cause local symptoms (e.g., frequency, dysuria), but rarely causes systemic symptoms (e.g., fever, septic shock).
  • Pyelonephritis is a common cause of bacteremia and septic shock.
• Over time, most patients with a urinary catheter will develop bacterial colonization of their bladders. This is also commonly seen in normal elderly people as well, even without having urinary catheters (asymptomatic bacteriuria).
  • This colonization is generally noninvasive and limited to the bladder, rather than ascending to the kidneys (unless there is obstruction, urologic surgery, or neutropenia). The Foley catheter itself plus ongoing urine flow tends to prevent invasive infection. However, some patients may develop invasive infection after the Foley catheter is removed, if there is subsequent urinary stasis and reflux into the kidneys.
• Catheter associated-urinary tract infection (CAUTI) is generally over-diagnosed, because the urine is easily cultured and often yields bacteria. In reality, these bacteria are usually not causing disease.
  • Finding bacteria in the urine is easy; the challenging issue is determining whether they are causing disease.

is CAUTI real?

• CAUTI does exist, but it is vastly less common than usually believed.
• One study prospectively evaluated 1,034 hospitalized patients with new Foley catheters and no alternative focus of infection. 89 patients (9%) developed >1,000 bacteria/ml in their urine. However, comparing patients who developed bacteriuria versus those who did not, there was no difference in the frequency of urgency, dysuria, fever, or leukocytosis! Thus, the vast majority of patients who develop bacteriuria have asymptomatic bacteriuria.(10724054)
• There is a notable absence of evidence that either of the following statements is valid:
  • CAUTI commonly causes symptoms (or necessarily exists, among patients with a functional Foley catheter).
  • Treatment of bacteriuria in hospitalized patients with an indwelling Foley catheter is beneficial.

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diagnostic approach to CAUTI

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#1) when to suspect CAUTI?

don't pay attention to cloudy or odorific urine

• Cloudy or malodorous urine shouldn't trigger evaluation for CAUTI.
• Urine usually doesn't smell like fine wine.

symptoms of CAUTI can be tricky

• CAUTI is rarely a cause of fever or delirium. (23878765)
  • It's unusual for urinary tract infection to be a cause of fever in the absence of urological procedures, neutropenia, or Foley dysfunction. (23878765, 18379262)
• Symptoms of bladder irritation (e.g., frequency, dysuria, urgency):
  • For a patient with a urinary catheter, these are nonspecific (because they can be caused by direct irritation from the catheter).
  • For a patient whose catheter has been removed, these symptoms should be considered as potential symptoms of infection (note that CAUTI may be diagnosed in patients whose catheter has been removed within <48 hours).

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#2) evaluate Foley catheter functionality & check urinalysis

This might be the single most important investigation to perform in a patient with possible CAUTI.

• If the Foley catheter is dysfunctional, this creates a much higher risk of pyelonephritis, septic shock, and obstructive renal failure. Urinary obstruction is an emergent problem that requires immediate attention (e.g., replacement of the foley catheter).
• If the Foley catheter is draining urine normally, this makes the likelihood of an invasive bacterial infection much less likely.

how to evaluate the Foley catheter

• Ideally: POCUS to exclude a distended bladder:
  • The finding of a distended bladder indicates dysfunction of the Foley catheter. This indicates a true risk of pyelonephritis, septic shock, and obstructive renal failure.
  • A non-distended bladder indicates normal function of the Foley catheter.
• Alternative: ensure that the Foley catheter is flushing normally.

Bacteriuria in the presence of a well-functioning catheter is probably somewhat analogous to a drained abscess, in which drainage prevents additional infectious complications – Trautner BW and Morgan DJ (32324234)

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#3) replace Foley and check UA/Cx

⚠️ The Foley catheter should be replaced prior to obtaining a urine culture. Otherwise, the culture may be contaminated by bacterial growth within the foley catheter (which doesn't represent an invasive bacterial infection). This is recommended by the Infectious Diseases Society of America.  (37902340)

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#4) evaluate urinalysis & culture data

pyuria 

• Definition of pyuria?
  • Pyuria is generally defined as >10 WBC per high-power field. (31532742)
  • However, studies have used cutoffs varying between ~5-25 WBC per high-power field. (10724053, 35580716)
• The presence of pyuria is nonspecific: this can be caused by CAUTI or by sterile irritation of the bladder by the urinary catheter.
• The absence of pyuria argues against a diagnosis of CAUTI (unless the patient is neutropenic).

urine culture

• ⚠️ Over time, most urinary catheters will become colonized with bacteria (asymptomatic bacteriuria). This occurs at a rate of 3-10% per day, so nearly all patients catheterized for a month will have bacteriuria. (30241712) Consequently, the presence of bacteria doesn't necessarily indicate CAUTI.
• >100,000 colony-forming units per ml of a uropathological bacteria is generally considered positive.

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other tests

procalcitonin

• The role of procalcitonin in UTI requires further research. However, it does appear that procalcitonin >0.5 is sensitive for the detection of urinary tract infection with bacteremia.(27979420, 25944771)
• For patients in whom the clinical suspicion is low for CAUTI (e.g., no neutropenia, obstruction, or urologic surgery), a procalcitonin <0.5 ng/ml may support the decision to withhold antibiotics.

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treatment of CAUTI

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when to start antibiotics?

• It is unclear exactly when antibiotics should be started during the diagnostic evaluation for CAUTI.
  • For patients with clinical signs of septic shock or neutropenic fever, antibiotic initiation should not be delayed.
  • For patients with an isolated fever, antibiotics should generally be withheld pending additional investigation (fever isn't an indication for antibiotics!).

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initial antibiotic selection

causative bacteria

• Epidemiological studies of CAUTI show that most infections are caused by gram-negative bacilli:
  • E. coli may be most common (~25%).
  • Pseudomonas (~10-20%).
  • Klebsiella pneumoniae/oxytoca (~10%). (31532742)
• Occasional infections may occur due to Staphylococcus aureus or Enterococcus species.

how broad does initial coverage need to be?

• This is unclear.
• If the patient is stable (e.g., febrile, but not shocked), then it's unnecessary to empirically cover every possible bacteria.
  • Note that CAUTI would only rarely lead to clinical shock – so if the patient is in septic shock then alternative sources should be aggressively pursued.

initial coverage for stable patients

• Consider any available data:
  • Urinalysis with positive nitrites suggests an enterobacteriaceae.
  • Urine cultures may reveal preliminary data (e.g., gram-negative rods).
• 🏆 Ceftriaxone 1 gram IV daily is generally fine (especially if urinalysis is positive for nitrites).
• Ceftazidime might also be reasonable (improved gram-negative coverage, which makes sense for urinary tract infection).
• Aztreonam may be reasonable if there is higher concern about resistant gram-negatives (aztreonam provides good gram-negative coverage, without affecting gram-positive or anaerobic flora).

💡 Culture and sensitivity information should almost always be available within 48-72 hours. This should allow for narrowing and focusing of antibiotic therapy.

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antibiotic duration

• Available studies suggest that a 5-7 day course is sufficient. (26402541, 37592966, 31532742)
• For patients with neutropenia, pregnancy, or urological surgery longer courses could be considered.

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prevention

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avoid or limit Foley catheter placement

• Review the need for a Foley catheter daily (similarly to ongoing review for a central line).

alternatives to bladder catheterization?

• These include a condom catheter for men or an external female collection device for women (e.g., PureWick).
• Although intuitively these devices might seem safer, they are not supported by robust data among ICU patients.

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podcast

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questions & discussion

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To keep this page small and fast, questions & discussion about this post can be found on another page here.

• Urinalysis should not be checked simply due to cloudy or odorous urine (Class A recommendation from Infectious Diseases Society of America). This probably represents colonization of the Foley bag, not invasive infection.
• Be careful about blaming fever and sepsis on CAUTI. CAUTI is a rare cause of severe illness, so it's probable that something else is going on (e.g., ventilator-associated pneumonia or line infection). Prematurely anchoring on the diagnosis of CAUTI could cause another focus of infection to be overlooked.
• Lower urinary tract symptoms (e.g., frequency, dysuria) may be due to irritation of the bladder by the catheter itself, rendering them nonspecific and unhelpful.

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