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Epidemiology

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Urinary tract infection (UTI) is described by location: urethritis, cystitis, or pyelonephritis. UTI is significant bacteriuria in the presence of symptoms. More than one third of women in the U.S. are diagnosed with a UTI by the time they are 24 years old. In women the lifetime risk for one or more UTIs exceeds 60%. UTIs account for at least 1 million ED visits, 7 million office visits, and 100,000 hospitalizations every year in the U.S. About 20% of all UTIs occur in men. UTI is the second most common form of infection, representing up to 25% of all infections and over 20% of all hospital-acquired infections. The estimated U.S. annual cost of community-acquired UTI is at least $1.6 billion currently.1–3 In school-aged children, UTI incidence rises with age to 5% and occurs almost exclusively in girls. The incidence of infection in postmenopausal women also increases with age. The prevalence of bacteruria among elderly women in nursing homes exceeds 40%.

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Neonates, girls (see Chapter 126, Urinary Tract Infection in Infants and Children), young women, and older men are the four age groups at increased risk for infection.1–4

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UTI in healthy young women is associated with the following risk factors: sexual activity, specifically increased intercourse frequency in the previous month, spermicide or diaphragm use, or a new sex partner in the previous 12 months; age at first UTI of <15 years; and history of UTI in the patient’s mother. The relationship between intercourse and UTI is sufficiently strong that recurrent UTI has been proposed as a possible marker for teenage sex.

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In males <50 years of age, the symptoms of dysuria or urinary frequency are usually due to a sexually transmitted disease (STD)–related infection of the urethra or prostate. However, in men >50 years, the incidence of UTI rises dramatically because of prostatic obstruction or subsequent instrumentation. By their eighth decade, more than one third of men will have had an episode of bacteriuria and one quarter will have been diagnosed with prostatitis.3

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Pathophysiology

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Urethritis and Cystitis

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Urethritis and cystitis are infections of the lower urinary tract system. Given the appropriate symptoms of dysuria, frequency, and urgency, the best diagnostic standard is a positive result on urine culture of ≥1000 colony-forming units (CFU)/mL.2,4,5 Acute cystitis is infection isolated to the bladder. Competent ureteral valves prevent ascent of the bacteria into the kidneys in most cases. Acute cystitis in otherwise healthy, nonpregnant young females with no obstruction is generally regarded as a benign illness if treated appropriately.

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Pyelonephritis

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Pyelonephritis is an infection of the upper urinary tract. Acute pyelonephritis is infection of the renal parenchymal and pelvico-calyceal system with a clinical syndrome of flank pain or costovertebral angle (CVA) tenderness, fever, and frequently other systemic symptoms such as nausea or vomiting.

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Uncomplicated Urinary Tract Infection

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Uncomplicated UTI is defined as UTI without structural or functional abnormalities within the urinary tract or kidney parenchyma, without relevant comorbidities that place the patient at risk for more serious adverse outcome, and not associated with GU tract instrumentation.1 The diagnostic standard is the isolation of 105 CFU/mL; however, ...

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