In 2015, urinary tract infection (UTI) was the seventh most common diagnosis in women older than 15 years of age presenting to EDs.1 Between 2006 and 2009, 10.8 million patients were evaluated in EDs due to UTIs, with 1.8 million admissions.2 Most visits for UTIs occur in younger women, with nearly half of all women experiencing a UTI during their lifetime.3 Starting at age 50, men experience an increasing frequency of UTIs as they grow older due to prostatic hypertrophy, debilitation, and instrumentation for relief of urinary obstruction.4 All age groups from neonates to the elderly are affected, with greater risks in special populations (see Chapter 135, “Urinary Tract Infection in Infants and Children,” and Chapter 99, “Comorbid Disorders 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 defined by several criteria:
The presence of >100,000 (>105) colony-forming units (CFU)/mL of a single pathogen on two successive clean-catch urine cultures in a woman without symptoms.5
The presence of >100,000 (>105) CFU/mL on one clean-catch urine culture in asymptomatic men.
The presence of 100 CFU/mL of a single isolate in a catheterized urine specimen in a patient without symptoms.
Prevalence of asymptomatic bacteriuria is 3.5% in the general population, but can be up to 10% in pregnant woman, 30% in male and 55% in female residents of nursing homes, and up to 100% in patients with indwelling catheters for more than 1 month.4 Treatment of asymptomatic bacteriuria is recommended only in pregnant women (see Chapter 99, “Comorbid Disorders in Pregnancy”) and in patients immediately prior to invasive urinary procedures in which mucosal bleeding may occur.5
Infections of the lower urinary tract include urethritis and cystitis. Acute cystitis is an infection and inflammation isolated to the bladder. Cystitis from an infection typically starts with colonization of the urethra by a pathogen from the GI system, which migrates into the bladder. Cystitis is typically diagnosed clinically by presence of dysuria, urinary frequency, and hematuria. Urine cultures in as many as 30% to 50% of women with cystitis have 100 to 10,000 CFU/mL, which may be reported as negative by some laboratories.6 Urethritis, commonly associated with sexually transmitted diseases, presents with similar symptoms but typically is associated with a discharge, lesions, or irritation. In women who have dysuria and urinary frequency without vaginal discharge or irritation, the probability of cystitis increases to greater than 90%.7
Pyelonephritis is an infection of the upper urinary tract. Acute pyelonephritis is infection of the renal parenchymal and pelvicalyceal system. Pyelonephritis ...