Urinary tract infection

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Urinary tract infections (UTI) are infections of the urinary tract. They are are second in incidence only to infections of the respiratory tract, with an estimated 8 million office visits annually in the USA. UTI is usually identifed as the most common cause of bacteremia in the community, hospital, and nursing homes. The majority of UTI infections occur in women, with as many as 20% of all women experiencing an episode of UTI at the age of 30. Recurrent episodes afflict about 1:10 of women at some time in their lives.

Urinary tract infections can affect all areas of the urinary tract, but the most common UTIs are those of the bladder (cystitis) and kidney (pyelonephritis). Urethritis can also occur alone. In males, chronic prostatic infection may lead to recurrent UTIs. Pyelonephritis may be complicated by bacteremia and if untreated may lead to sepsis.

Pathogenesis

Most UTIs are caused by fecal organisms — especially Escherichia coli — that are inadvertently introduced into the periurethral area, with anatomic differences between female and male urethras acting as a host factor. Hematogenous infection is rare and usually affects the kidneys (e.g., tuberculosis). Some bacterial clones are more likely to be associated with pyelonephritis than cystitis.

Treatment

For a treatment to be effective, the antibiotic of choice has to be eliminated by the kidney. Recurrent infections require culturing and determination of antimicrobial susceptibility for therapeutic decision.

Asymptomatic bacteriuria requires treatment in the case of pregnant women, preschool children, patients with structurally abnormal urinary tracts, and patients that will undergo instrumentation of the urinary tract. In other cases, additional more specialized studies may be required, especially to evaluate reflux and anatomical anomalies.

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