2.2 Background

Acute, uncomplicated UTIs in adults include episodes of acute cystitis and acute pyelonephritis occurring in otherwise healthy individuals. These UTIs are seen mostly in women who have none of the factors that are known to increase the risks of complications or of treatment failure. Uncomplicated UTIs are extremely common infections. Approximately 25-35% of women between the ages of 20 and 40 years have experienced an episode described by their physician as an uncomplicated UTI (1).

2.3 Definition

The distinction between an uncomplicated and a complicated UTI is important because of implications with regard to pre- and post-treatment evaluation, the type and duration of antimicrobial regimens, and the extent of the evaluation of the urinary tract. A complicated UTI is an infection associated with a condition that increases the risks of acquiring an infection or of failing therapy. At the time of presentation with an acute onset of urinary tract symptoms, it is usually not possible to classify definitively patients as having a complicated or an uncomplicated UTI. Several factors have been identified, however, that are markers for a potential complicated UTI (Table 1).

Table 1: Factors that suggest a potential complicated UTI (modified according to ref 2)

Male sex

Elderly

Hospital-acquired infection

Pregnancy

Indwelling urinary catheter

Recent urinary tract intervention

Functional or anatomical abnormality of the urinary tract

Recent antimicrobial use

Symptoms for > 7 days at presentation

Diabetes mellitus

Immunosuppression

These factors serve only as guidelines to the clinician who must decide, based on limited clinicalinformation, whether to embark on a more extensive evaluation and treatment course. It is generally safe to assume that a pre-menopausal, non-pregnant woman with acute onset of dysuria, frequency or urgency, who has not recently been instrumented or treated with antimicrobials and who has no history of a genitourinary tract abnormality, has an uncomplicated lower (cystitis) or upper (pyelonephritis) UTI. Recurrent UTIs are common among young, healthy women, even though they generally have anatomically and physiologically normal urinary tracts.

Whether a UTI in pregnancy by itself is to be classified as an uncomplicated or a complicated UTI remains debatable. Although data on UTIs in healthy post-menopausal women without genitourinary abnormalities are limited, it is likely that most UTIs in such women are also uncomplicated. Data on UTIs in healthy adult men are sparse and much less is known about the optimal diagnosis of, and therapeutic approaches for, such UTIs.

2.4 Aetiological spectrum

The spectrum of aetiological agents is similar in uncomplicated upper and lower UTIs, with E. coli being the causative pathogen in approximately 70-95% of cases and S. saprophyticus in over 5% of cases. Occasionally, other Enterobacteriaceae, such as P. mirabilis and Klebsiella spp., or enterococci, are isolated from such patients. In as many as 10-15% of symptomatic patients, bacteriuria cannot be detected using routine methods.