Complicated Urinary Tract Infections

Definition and Factors

• A complicated urinary tract infection (UTI) occurs when an individual has host-related factors or specific anatomic or functional abnormalities in the urinary tract that make the infection more challenging to eradicate compared to an uncomplicated infection, as defined by the European Urology guidelines 1, 2
• Obstruction at any site in the urinary tract is a factor that defines a complicated UTI, according to the European Urology guidelines 1
• Presence of foreign bodies, including indwelling catheters, is a factor that defines a complicated UTI, as stated by the European Urology guidelines 1
• Incomplete voiding is a factor that defines a complicated UTI, as defined by the European Urology guidelines 1
• Vesicoureteral reflux is a factor that defines a complicated UTI, according to the European Urology guidelines 1
• Recent history of instrumentation is a factor that defines a complicated UTI, as stated by the European Urology guidelines 1
• Urinary tract diverticula or fistulae are anatomical abnormalities that can contribute to complicated UTIs, as reported by the Journal of the American College of Radiology 3
• Male gender is a host-related factor that defines a complicated UTI, as all UTIs in men are considered complicated, according to the European Urology guidelines 1
• Pregnancy is a host-related factor that defines a complicated UTI, as stated by the European Urology guidelines 1
• Diabetes mellitus is a host-related factor that defines a complicated UTI, according to the European Urology guidelines 1
• Immunosuppression is a host-related factor that defines a complicated UTI, as defined by the European Urology guidelines 1
• Healthcare-associated infections are a host-related factor that defines a complicated UTI, as stated by the European Urology guidelines 1
• Voiding dysfunction is a host-related factor that can contribute to complicated UTIs, as reported by the Journal of the American College of Radiology 3

Microbiological Factors

• Infections with ESBL-producing organisms are a microbiological factor that defines a complicated UTI, according to the European Urology guidelines 1
• Multidrug-resistant organisms are a microbiological factor that defines a complicated UTI, as stated by the European Urology guidelines 1
• Broader microbial spectrum than uncomplicated UTIs is a characteristic of complicated UTIs, as defined by the European Urology guidelines 1
• Common pathogens include E. coli, Proteus spp., Klebsiella spp., Pseudomonas spp., Serratia spp., and Enterococcus spp., as reported by the European Urology guidelines 1

Clinical Considerations

• Complicated UTIs require longer treatment duration (7-14 days) compared to uncomplicated UTIs, as recommended by the European Urology guidelines 4
• Men with UTIs typically need 14 days of treatment when prostatitis cannot be excluded, according to the European Urology guidelines 4
• Complicated UTIs require management of the underlying urological abnormality or complicating factor, as stated by the European Urology guidelines 4
• Complicated UTIs often necessitate broader antimicrobial coverage due to increased risk of resistant organisms, as recommended by the European Urology guidelines 4
• Urine culture and susceptibility testing should always be performed before initiating therapy, as recommended by the European Urology guidelines 1
• Initial empiric therapy should be tailored based on local resistance patterns and patient factors, according to the European Urology guidelines 1

Important Distinctions

• Uncomplicated UTI occurs in patients without structural or functional abnormalities and without relevant comorbidities, as defined by the Journal of the American College of Radiology 3
• Repeated episodes of pyelonephritis should prompt consideration of a complicated etiology, as reported by the Journal of the American College of Radiology 3
• Catheter-associated UTIs (CA-UTIs) are always considered complicated, according to the European Urology guidelines 5
• Inadequate antimicrobial coverage may lead to treatment failure due to higher likelihood of resistant organisms, as stated by the European Urology guidelines 1
• Overlooking the need for longer treatment duration in complicated UTIs compared to uncomplicated cases can lead to poor outcomes, as recommended by the European Urology guidelines 4

Definition and Clinical Management of Complicated Urinary Tract Infections

Definition

• A complicated urinary tract infection is a symptomatic urinary infection occurring in individuals with functional or structural genitourinary abnormalities, or host‑related factors that increase the risk of treatment failure, persistent infection, or serious complications. 6

Guideline Classification

• The 2024 European Association of Urology (EAU) guidelines provide the current framework for classifying complicated urinary tract infections. 7

Clinical Outcomes

• Complicated UTIs have a higher risk of progression to urosepsis, with approximately 10 % mortality when bacteremia develops. 7

Diagnostic Recommendations

• The EAU 2024 guidelines mandate obtaining a urine culture and susceptibility testing before initiating antimicrobial therapy for all suspected complicated UTIs. 7

Empiric Antimicrobial Therapy

• For patients with systemic symptoms, empiric combination therapy is recommended: amoxicillin plus an aminoglycoside, or a second‑generation cephalosporin plus an aminoglycoside, or an intravenous third‑generation cephalosporin. 7
• Fluoroquinolones should be avoided as empiric agents when local resistance exceeds 10 %, when the patient has used them within the previous six months, or in patients managed in urology departments. 7

Management of Underlying Urological Abnormalities

• Addressing and correcting the underlying urological abnormality (e.g., obstruction, foreign body, functional impairment) is mandatory; antimicrobial therapy alone will fail without such correction. 7

Catheter‑Associated Urinary Tract Infections

• Symptomatic catheter‑associated UTIs are to be managed using the same protocols as other complicated UTIs. 7
• The incidence of bacteriuria rises by 3–8 % for each day a urinary catheter remains in place. 7
• Asymptomatic bacteriuria in catheterized patients should not be treated, except prior to invasive urologic procedures. 7
• Treating catheter‑associated asymptomatic bacteriuria is discouraged because it promotes antimicrobial resistance without clinical benefit. 7