Complicated Urinary Tract Infection (UTI)

Background

• Complicated UTI is defined as an infection of either the upper or lower urinary tract in a patient that is at an increased risk for failing treatment or complications.
• Risk factors for complicated UTI include both functional and structural abnormalities of the urinary tract, such as neurogenic bladder, instrumentation, or obstruction.
• Some experts consider UTI in a patient with metabolic abnormalities, such as diabetes mellitus or in patients with immunocompromising conditions, complicated as well.
• The spectrum of pathogens causing infection in complicated UTI is more diverse than that of uncomplicated UTI.
  • Escherichia coli is the most common pathogen followed by other enteric gram-negative rods.
  • Other pathogens include Pseudomonas species and gram-positive organisms such as enterococci and staphylococci.
• Systemic complications, such as sepsis, are more common than with uncomplicated UTI.
• Local complications are uncommon but include renal abscess, perinephric abscess, and papillary necrosis.

Evaluation

• Cystitis typically presents with urinary frequency, dysuria, suprapubic pain, and urgency.
• Pyelonephritis often presents with flank pain, fever, chills, nausea, and vomiting.
• Presentation may be subtle or atypical in elderly, immunocompromised, catheterized, obstructed, and neurologically impaired patients.
• In most cases, diagnosis requires the presence of significant bacteria in urine culture, defined as:
  • bacterial count ≥ 10⁵ colony-forming units (CFU)/mL in 2 consecutive midvoid urine samples for women.
  • bacterial count ≥ 10 ⁵ CFU/mL in a single midvoid urine sample for men.
  • bacterial count ≥ 10 ²CFU/mL in a single urine sample from patients with catheters.
• Sterile urine or lower colony counts may be present in patients with urinary obstruction, as bacterial growth may be proximal to site of obstruction.
• Consider computed tomography or ultrasound in patients with a suspected urinary tract abnormality, such as stricture or stone, or if a complication such as an abscess is suspected.

Management

• Select empiric antibiotic based on the severity of illness, local epidemiology, and the history of resistant microorganisms in the individual patient:
  • For mild-to-moderately ill patients consider fluoroquinolones with good urinary tract penetration if risk of fluoroquinolone resistance is known to be low and no contraindications, such as:
    • ciprofloxacin 500 mg orally twice daily or 400 mg IV every 12 hours
    • levofloxacin 500 mg/day orally or IV
  • For severely ill patients or those at risk for having fluoroquinolone-resistant organisms, broader coverage is recommended; options include:
    • cefepime 2 g IV every 12 hours
    • ceftazidime 2 g IV every 8 hours
    • piperacillin-tazobactam 3.375-4.5 g IV every 6 hours
    • meropenem 1 g IV every 8 hours
  • For severely ill patients at risk for enterococcal infection, consider addition of:
    • ampicillin 1-2 g IV every 6 hours
    • vancomycin 15 mg/kg IV every 12 hours
    • daptomycin 4 mg/kg IV once daily (if vancomycin-resistant Enterococcus is suspected)
    • linezolid 600 mg orally or IV every 12 hours (if vancomycin-resistant Enterococcus is suspected)
  • Consider addition of vancomycin 15 mg/kg IV every 12 hours in severely ill patients with risk for other gram-positive infections (if vancomycin, daptomycin, or linezolid not added as above) due to:
    • gram-positive cocci on Gram stain
    • known or suspected colonization with methicillin-resistant Staphylococcus aureus
    • recent instrumentation such as prostate biopsy or catheterization
  • For patients with suspected gram-positive infection, such as a history of enterococcal infection, recent instrumentation or gram-positive cocci on Gram stain, consider the addition of vancomycin.
• Definitive therapy should be based on culture and susceptibility results.
• The above antibiotic dosing may need adjustment based on renal function.
• The duration of therapy is typically individualized based on underlying condition and severity of illness.
• The European Association of Urology (EAU) recommends 7-14 days for most cases but courses as short as 5 days have been reported to be effective in clinical trials.
• Relieve obstruction immediately in severely ill patients when present, such as with passage of Foley catheter for lower tract obstruction or urologic consultation for impacted stone or other abnormalities obstructing urinary outflow.
• Consider the removal of any potential nidus for recurrent or relapsed infection such as a nonobstructing stone or an indwelling catheter.