Chapter 64 Urinary Tract Infection
INTRODUCTION
Description: An infection of the urinary tract causes urethritis, cystitis (including trigonitis), or pyelonephritis. Urinary tract infections (UTIs) are much more common in women because of their shortened urethral length and exposure of the urinary tract to trauma and pathogens during sexual activity.
Prevalence: Seen in 3% to 8% of patients (second most common type of infection in the body, 8.3 million visits per year), with roughly 45% of women aged 15 to 60 experiencing at least one UTI.
ETIOLOGY AND PATHOGENESIS
Causes: Most UTIs in women ascend from contamination of the urethra, acquired via instrumentation, trauma, or sexual intercourse. (A history of intercourse within the preceding 24 to 48 hours is present in up to 75% of patients with acute UTI.) Coliform organisms, especially Escherichia coli, are the most common organisms responsible for asymptomatic bacteriuria, cystitis, and pyelonephritis. Ninety percent of first infections and 80% of recurrent infections are caused by E. coli, with between 10% and 20% resulting from Staphylococcus saprophyticus. Infection with other pathogens such as Klebsiella species (5%) and Proteus species (2%) account for most of the remaining infections. Anaerobic bacteria, Trichomonas, and yeasts are rare sources of infections except in patients with diabetes, patients who are immunosuppressed, or those requiring chronic catheterization. Infection with Neisseria gonorrhoeae, Chlamydia trachomatis, Mycoplasma, and Ureaplasma should all be considered when urethritis is suspected.
