Urinary tract infection (UTI) is complicated if the UTI is associated with factors that increases colonization and decreases therapy efficacy. Factors may include one or all of the following: Structural or functional abnormalities of the genitourinary tract; presence of an underlying disease that interferes with host defense mechanisms or the patient being immunocompromised; and being infected by a multi-drug resistant bacteria.
Principles of therapy includes effective antimicrobial antimicrobial therapy, optimal management of the underlying abnormalities or other diseases & adequate life-supporting measures.

Principles of Therapy

General Therapy Principles

  • The successful treatment of a complicated urinary tract infection (UTI) considers effective antimicrobial therapy, optimal management of the underlying abnormalities or other diseases & adequate life-supporting measures
  • Patients w/ complicated UTIs generally require 7-14 days of antimicrobial therapy

Oral vs Parenteral Therapy

  • Oral antibiotic therapy may be started in stable patients
  • Initial parenteral therapy is preferred only for individuals who have: Hemodynamic instability, nausea & vomiting, questionable absorption or an infection by suspected resistant organisms for which oral therapy is not available
    • Patients may be switched to appropriate oral therapy w/in 72 hours if showing clinical improvement & if they can tolerate oral medications

Empiric Treatment

  • The selection of a specific antimicrobial agent is based upon clinical presentation, the known or suspected microorganism & its susceptibilities, patient tolerance, documented efficacy & in some cases, cost
  • Should immediately be replaced w/ specific treatment once pathogen is detected in urine culture since intense use of any antimicrobial will lead to the emergence of resistant microorganisms



  • One of the treatments of choice if parenteral therapy is needed
  • Depending on suspected etiologic agent, may be used as initial therapy or reserved as an alternative therapy
    • May be combined w/ beta-lactam w/ or w/o pseudomonal coverage (many times an aminopenicillin is used as initial therapy) 
  • Effective against several resistant microorganisms

Aminopenicillin w/ Beta-lactamase Inhibitor

  • Synergistic action w/ beta-lactamase inhibitor causes these agents to be more active than aminopenicillins alone
    • Efficacious in Gram-positive microorganisms (eg group B streptococci & Enterococcus sp) 
  • Aminopenicillins alone are no longer sufficiently active againstE coli & therefore should not be used as empiric therapy
    • Depending on local antimicrobial resistance patterns, aminopenicillins in combination w/ aminoglycosides may be used for empiric therapy

Antipseudomonal Penicillin w/ Beta-lactamase Inhibitor

  • May be used in case of failure of initial empiric therapy or for severe cases


  • Appropriate empiric parenteral therapy in hospitalized patients who fail to respond to initial antibiotic therapy or in patients in whom the bacteria is known to be resistant to other agents


Doripenem, Imipenem/cilastatin or Meropenem

  • Appropriate empiric parenteral therapy in hospitalized patients who fail to respond to initial antibiotic therapy or in patients in whom the bacteria is known to be resistant to other agents

Cephalosporins (1st, 2nd & 3rd Generation)

  • Oral 1st, 2nd or 3rd generation cephalosporins may be appropriate for patients w/ mild-moderate complicated urinary tract infection (UTI)
  • IV 2nd or 3rd generation cephalosporins may be used as initial empiric therapy in hospitalized patients
  • IV 3rd or 4th generation cephalosporins may be used in case of initial empiric therapy failure
    • Ensure that 3rd generation cephalosporin to be used was not previously administered & has antipseudomonal coverage

Co-trimoxazole [Sulfamethoxazole (SMZ) & Trimethoprim (TM)]

  • Should be avoided as empiric therapy since most countries have high rates of E coli resistance to Co-trimoxazole
  • Can be considered if susceptibility is known


  • Oral quinolones are appropriate as initial empiric therapy in patients w/ mild-moderate complicated UTIs
  • IV quinolones may be used for severe cases
  • Quinolones may be used if initial therapy fails as long as initial therapy was not a quinolone
  • Should be administered orally as much as possible

Specific Therapy

Complicated Urinary Tract Infection (UTI) Associated w/ Indwelling Catheter

  • Symptomatic complicated UTIs occurring in patients w/ a short-term indwelling catheter should be treated by removing the catheter & w/ administration of a narrow-spectrum antibiotic based on culture & sensitivity results
  • Replace or remove catheter before starting antibiotics if indwelling catheter has been in place >7 days
  • Asymptomatic bacteriuria should not be treated regardless whether or not the patient has short-term or long-term catheter, except in certain situations eg prior to traumatic urinary tract procedures
  • Antibiotic prophylaxis is not recommended for preventing catheter-related UTI

Complicated Urinary Tract Infection (UTI) Associated w/ Urinary Stones

  • Urinary obstruction w/o evidence of infection may be treated expectantly
  • Empiric, broad-spectrum antimicrobials should be started immediately in patients that have clinical signs of infection
  • Efforts to remove the stone should only be considered once the infection has cleared but early intervention to relieve the obstruction using a stent or nephrostomy tube is frequently necessary
  • If complete removal of the stone cannot be accomplished, long-term antibiotic therapy may be considered

Complicated Urinary Tract Infection (UTI) in Spinal Cord-Injured Patients

  • The presence of residual urine & bladder outlet obstruction (anatomic or physiologic) predisposes this group of patients to UTI
  • Symptomatic episodes of infection should be treated w/ antimicrobials
    • There is no superiority of 1 agent or class of antimicrobials over another 
  • Asymptomatic bacteriuria should not be treated

Complicated Urinary Tract Infection (UTI) Associated w/ Diabetes Mellitus (DM)

  • 7-14 days of antimicrobial therapy is recommended
  • DM patients who present w/ UTI & signs & symptoms of sepsis should be hospitalized
    • Failure to respond w/in 48-72 hours requires plain abdominal radiograph & renal ultrasound
  • Asymptomatic bacteriuria in diabetics should not be treated routinely w/ antibiotics
    • A history of febrile UTI & other concomitant conditions are factors to be considered when deciding on starting antibiotic treatment for diabetics w/ asymptomatic bacteriuria

Complicated Urinary Tract Infection (UTI) in Renal Transplant Patients

  • Effective antibiotic therapy requires the use of antibiotics that achieve therapeutic concentration in the urine & are appropriately dose-adjusted for the level of renal failure
  • Initially, treat w/ parenteral broad-spectrum antibiotics until urine culture becomes negative
  • May be shifted to oral agents guided by culture & sensitivity results to complete 4-6 weeks
  • 10-14 days of antibiotic treatment is required in most cases
  • Asymptomatic bacteriuria that occurs during the first 6 months after transplantation may often need to be treated w/ antibiotics
    • Low-dose Co-trimoxazole antibiotic prophylaxis has been recommended for 6 months posttransplant

Urinary Tract Infection (UTI) in Pregnant Women

  • Progression of cystitis & asymptomatic bacteriuria to pyelonephritis is significantly increased in pregnant women
  • Pregnant women should be screened for asymptomatic bacteriuria through a quantitative urine culture at first prenatal visit, ideally at 16 weeks of gestation 
    • If positive, confirm through a 2nd culture
    • Treat both symptomatic & asymptomatic bacteriuria w/ antibiotics
    • Obtain specimen for urine culture before starting treatment
  • Repeat urine culture 7-14 days after completing antibiotic treatment
    • Repeat urine culture at each prenatal visit until delivery
  • If urine culture during 1st prenatal visit is negative, it is unnecessary to repeat urine culture during subsequent prenatal visits
  • For cystitis, penicillins, cephalosporins & Nitrofurantoin are recommended
  • For pyelonephritis, aminopenicillins w/ or w/o a beta-lactamase inhibitor & cephalosporins are mainstays; aminoglycosides may be used w/ caution
    • Most pregnant women will need hospitalization & parenteral antibiotics
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