Urinary tract infection (UTI) is a common and painful human illness that is rapidly responsive to modern antibiotic therapy, if the correct antibiotic is chosen for the particular urinary pathogen. In the preantibiotic era, UTI caused significant morbidity. Hippocrates, writing about a disease that appears to have been acute cystitis, said that the illness could last for a year before either resolving or worsening to involve the kidneys. When chemotherapeutic agents used to treat UTI were introduced in the early twentieth century, they were relatively ineffective, and persistence of infection after 3 weeks of therapy was common. Nitrofurantoin, which became available in the 1950s, was the first tolerable and effective agent for the treatment of UTI.
Since the most common manifestation of UTI is acute cystitis and since acute cystitis is far more prevalent among women than among men, most clinical research on UTI has involved women. Many studies have enrolled women from college campuses or large health maintenance organizations in the United States. Therefore, when reviewing the literature and recommendations concerning UTI, clinicians must consider whether the findings are applicable to their patient populations.
UTI may be asymptomatic (subclinical infection) or symptomatic (disease). Thus, the term urinary tract infection encompasses a variety of clinical entities, including asymptomatic bacteriuria (ASB), cystitis, prostatitis, and pyelonephritis. The distinction between symptomatic UTI and ASB has major clinical implications. Both UTI and ASB connote the presence of bacteria in the urinary tract, usually accompanied by white blood cells and inflammatory cytokines in the urine. However, ASB occurs in the absence of symptoms attributable to the bacteria in the urinary tract and usually does not require treatment, while UTI has more typically been assumed to imply symptomatic disease that warrants antimicrobial therapy. Much of the literature concerning UTI, particularly catheter-associated infection, does not differentiate between UTI and ASB. In this chapter, the term urinary tract infection denotes symptomatic disease; cystitis, symptomatic infection of the bladder; and pyelonephritis, symptomatic infection of the kidneys. Uncomplicated urinary tract infection refers to an infection confined to the bladder, or acute cystitis. Pyelonephritis occurs when the infection involves the renal parenchyma. Complicated urinary tract infection is accompanied by symptoms that suggest the infection extends beyond the bladder, such as a fever or signs or symptoms of systemic illness. Recurrent urinary tract infection is not necessarily complicated; individual episodes can be uncomplicated and treated as such. Catheter-associated bacteriuria can be either symptomatic (CAUTI) or asymptomatic. This new approach to UTI categorization differs from the classical approach, in which men with UTI are automatically considered complicated. This updated categorization more closely reflects actual clinical practice. The key considerations in diagnostic workup and therapy for UTI are whether the patient is stable for outpatient management and whether the antimicrobial agents need to achieve adequate levels in blood and tissue.
EPIDEMIOLOGY AND RISK FACTORS