Catheter Associated Urinary Tract Infection

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Catheter Associated Urinary Tract Infection

Catheter Associated Urinary Tract Infection

Catheter associated urinary tract infection (CAUTI) is one of the most frequently encountered healthcare associated infections today. Indwelling urinary catheters frequently become colonised with micro-organisms but the majority of cases will be asymptomatic. Differentiation between such colonisation and CAUTI is important for patient management, but unfortunately is not straightforward. This article discusses the diagnosis, causative microbiology and pathogenesis of CAUTI, and briefl y considers complications of catheterisation and how these might be prevented.


The urethral catheter has been in use as a medical device for centuries. From the development by Foley of the fi rst ballooninfl ating device in the 1920s, to the evolution of the 'closed' drainage systems in the 1950s and 1960s, the urinary catheter today is one of the most widely used pieces of medical apparatus. Each year millions of urinary catheters are placed in patients in acute care hospitals, rehabilitation units and chronic care facilities. Unfortunately these devices are not without risk. (Zheng and Shetty 2000)

Healthcare associated infection is estimated to affect one in ten NHS hospital patients each year, of which urinary infection accounts for roughly 23%. Of these, 80% are traced to the use of indwelling urinary catheters (IDC). This may not be surprising since the use of urethral catheters is very common; urinary incontinence alone affects about 50% of the elderly population and up to 25% of patients may receive a catheter during their hospital stay. The prevalence of IDC has been estimated at 12.6% in acute hospitals in England and 9% of registered nursing home residents, but may be 40% or more in some types of nursing homes. (Wilson and Harbin 2008) One prospective study of elderly nursing home residents in the US found that over a 12 month period, catheterised patients were three times more likely to receive antibiotics, be hospitalised and die within a year compared with matched non-catheterised patients.

Furthermore, catheter associated urinary tract infection (CAUTI) may account for up to 15% of hospital acquired bacteraemias. In this article we will discuss the diagnosis, causative microbiology and pathogenesis of CAUTI, and briefly consider complications of catheterisation and how these might be prevented.

What is CAUTI and how is it diagnosed?

We fi rst need to establish what we mean by catheter associated urinary tract infection. In particular, we must differentiate catheter colonisation from infection. Bacteriuria is a term which simply means that bacteria have been cultured from the urine. Bacteriuria is strongly associated with the length of time the catheter is in situ, i.e. the longer the catheter is in place, the higher the risk of bacteriuria. (Jackson and Hicks 2007)

The risk of developing bacteriuria increases by approximately 3-10% per day for each day a catheter remains in place. Ten to 30% of patients with a short-term catheter, i.e. less than 30 days, will develop bacteriuria as compared to 1% in non-catheterised patients. In contrast, up to 95% of long-term catheterised patients, i.e. 30 days or more, will become ...
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