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COMPLICATIONS OF URINARY CATHETERS
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Urinary catheters should be used sparingly. Indwelling urethral catheters are the most common; suprapubic catheters require a surgical procedure but have fewer infectious complications (see chapter 92, "Acute Urinary Retention"). Most catheters are made of latex; however, silicone catheters are available for patients with latex allergy.1 Table 95-1 lists the complications of urinary catheters.
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Catheter-associated urinary tract infections (UTIs) are one of the most common causes of nosocomial infections. The risk of infection is approximately 1% to 2% with a catheter in place for <24 hours, with the prevalence of bacteriuria reaching almost 100% for long-term catheterization (by 30 days).2 Comorbidities that increase the risk of catheter-associated UTI include female sex, prostatic hypertrophy, creatinine >2 milligrams/dL, diabetes, advanced age, nonsurgical disease, and debilitation.3 Microbial factors associated with an incidence of catheter-associated UTI include the source of the organisms, the specific bacteria, the route of invasion, and the duration of catheterization.
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In the noncatheterized urinary tract, bacteria are efficiently eliminated. In contrast, most bacterial strains that are introduced into the catheterized urinary tract are able to multiply to high concentrations in 24 hours. Bacteria may be able to gain access to the urinary tract through the catheter lumen (intraluminal) or along the catheter surface (extraluminal). The drainage tube of a urinary catheter must be opened periodically to drain the accumulated urine. If the drainage tube lumen is colonized, bacteria may ascend the collection bag and catheter, causing an infection. An infection from the catheter lumen route begins with the formation of a biofilm on the catheter's inner surface. This biofilm extends from the uroepithelium through catheters to the drainage bag and allows adherence of bacteria to a catheter or mucosal surface. Organisms become embedded within the biofilm and gain protection from the mechanical flow of urine, host defenses, and antibiotics.2 The microbiology of catheter-associated UTI varies according to the duration of catheter placement. During short-term catheterization, infections are usually due to single organisms, most commonly Escherichia coli, followed by Klebsiella, Pseudomonas, Enterobacter, and gram-positive cocci such as staphylococci. With long-term catheterization (≤30 days), catheter-associated UTIs are usually polymicrobial from E. coli, Proteus mirabilis, Pseudomonas, Morganella morganii, and Candida species. These infections are usually difficult to treat due to antibiotic resistance by the infecting bacteria.2
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Asymptomatic bacteriuria usually occurs ...