Urinary tract infections (UTIs) are among the most common causes of sepsis in hospitalized patients. UTIs have a wide variety of presentations. Some simple UTIs can be managed with outpatient antibiotics and carry a reassuring clinical course with an almost universally good outcome. On the other end of the spectrum, florid urosepsis in a comorbid patient can be fatal. UTIs can also be complicated by several risk factors leading to treatment failure, repeat infections, or significant morbidity and mortality with a poor outcome. It is essential to determine whether the presenting episode is associated with underlying risk factors and assess its likelihood of resolving with first-line antibiotics.
A complicated urinary tract infection (UTI) is an infection with a higher risk of treatment failure. Proper identification is crucial, as these infections often require longer treatment durations, alternative antibiotics, and sometimes additional diagnostic evaluations to ensure effective management.
A simple UTI (or cystitis) is a urinary tract infection due to appropriate susceptible bacteria in a clinical context not associated with treatment failure or poor outcomes. Typically, this is an infection in an afebrile, nonpregnant, immune-competent female patient. Pyuria and/or bacteriuria without any symptoms is not a UTI and may not require treatment. An example would be an incidental positive urine culture in an asymptomatic, afebrile, nonpregnant immune-competent female. A complicated UTI is any UTI other than a simple UTI, as defined above. Therefore, all UTIs in immunocompromised patients, males, pregnant patients, and those associated with fevers, stones, sepsis, urinary obstruction, catheters, or involving the kidneys are considered complicated infections.
The female urinary tract, with its relatively short urethra, is inherently predisposed to bacterial seeding and proximal spread. This anatomy increases the frequency of infections. Simple cystitis, a single episode of ascending pyelonephritis, and even recurrent cystitis in certain contexts may be classified as simple UTIs, provided they respond promptly to first-line antibiotics and result in no long-term complications.
Any UTI that does not conform to the above description or clinical trajectory is considered a complicated UTI. In these scenarios, one can almost always find protective factors that failed to prevent infection or risk factors that lead to poor resolution of sepsis, higher morbidity, treatment failures, and reinfection. The reason for the distinction is that complicated UTIs have a broader spectrum of bacteria as an etiology and have a significantly higher risk of clinical complications. The presence of urinary tract stones and catheters is likely to increase the incidence of recurrences compared to patients without these foci of bacterial colonization.
Examples of a complicated UTI include:
Infections despite the presence of anatomical protective measures (UTIs in males are, by definition, considered complicated UTIs)
Infections due to anatomical abnormalities, for example, an obstruction, hydronephrosis, renal tract calculi, or colovesical fistula
Infections due to an immunocompromised state, for example, steroid use, postchemotherapy, diabetes, HIV, older individuals
Atypical organisms causing UTI
Recurrent infections despite adequate treatment (multidrug-resistant organisms)
Infections occurring in pregnancy (including asymptomatic bacteriuria)
Infections occurring after instrumentation, such as placing or replacement of nephrostomy tubes, ureteric stents, suprapubic tubes, or Foley catheters
Infections in renal transplant and spinal cord injury patients
Infections in patients with impaired renal function, dialysis, or anuria
Infections following surgical prostatectomies or radiotherapy
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