In 2010, urinary tract infection (UTI) was the sixth most common diagnosis in women age 15 to 64 years and the fourth most common diagnosis in women age 65 years and older presenting to the ED.1 The self-reported annual incidence of UTI in women is 12%, and by the age of 32 years, half of all women report having had at least one UTI. Although younger women are more likely to be affected than men by a ratio of 35:1, the gender gap decreases to 2:1 by age 66, most likely due to prostatic hypertrophy and need for instrumentation in elderly men.2 All age groups from neonates to the elderly are affected, carrying risks in special populations. 3 (See chapters 132, "Urinary Tract Infection in Infants and Children" and 99, "Comorbid Diseases in Pregnancy").
PATHOPHYSIOLOGY AND DEFINITIONS
UTIs can be grouped based on the anatomic site involved as well as patient characteristics. These classifications are important when determining treatment modalities.
Asymptomatic bacteriuria is the presence of >100,000 (>105) colony-forming units (CFU)/mL of a single pathogen on two successive urine cultures in a patient without symptoms.4
Prevalence of asymptomatic bacteriuria is up to 10% in pregnant woman, 40% in male and 50% in female residents of nursing homes, and up to 100% in patients with indwelling catheters for more than 1 month. There is evidence to suggest that asymptomatic bacteriuria may provide some protection against symptomatic infection with invasive organisms in patients with indwelling catheters5 and in patients with recurrent UTIs.6 Treatment of asymptomatic bacteriuria is recommended only in pregnant woman (see chapter 99) and in patients immediately prior to invasive urinary procedures.4
Infections of the lower urinary tract include urethritis and cystitis. Acute cystitis is an infection isolated to the bladder. Acute cystitis without coexisting pyelonephritis in otherwise healthy, nonpregnant young females with no obstruction is a benign illness with a 24% spontaneous cure rate; less than 1% of patients go on to develop pyelonephritis.7 Competent ureteral valves prevent ascent of the bacteria into the kidneys in most cases. The diagnostic criterion in acutely symptomatic patients is a positive urine culture of ≥102 to >103 CFU/mL.8 Urethritis, commonly associated with sexually transmitted diseases, presents with similar symptoms but typically is associated with a vaginal discharge or irritation.
Pyelonephritis is an infection of the upper urinary tract. Acute pyelonephritis involves the renal parenchymal and pelvicalyceal system. Pyelonephritis is differentiated from cystitis primarily by clinical findings: a syndrome of flank pain or costovertebral angle tenderness, with or without fever, in the setting of a positive urine culture of 105 CFU/mL, and frequently other systemic symptoms such as nausea or ...