Urinary tract infection

Introduction

• Classified as urethritis, cystitis or pyelonephritis
• Defined as significant bacteriuria in presence of symptoms
• Risk factors in healthy young women:
  • Sexual activity
  • Spermicide or diaphragm use
  • New sex partner in last 12 months
  • Age at first UTI <15yo
  • Hx of UTI in patient’s mother
• Recurrent UTI may be a marker for teenage sex
• In males <50, symptoms usually due to STI of urethra or prostate

Urethritis/cystitis

• In the presence of symptoms (suprapubic tenderness, costovertebral angle pain or tenderness, urinary urgency or frequency, or dysuria), diagnostic standard of diagnosis is urine culture of >10^5 CFU/mL from a mid-stream urine sample
• Some definitions also include:
  • Pyuria >10 WCC/mm3/HPF
  • >10^3 CFU/mL if catheter-related
• In elderly patients, cloudy or malodourous urine does not require investigation in the absence of other symptoms/signs

Pyelonephritis

• Clinical syndrome of flank pain, costovertebral angle tenderness, fever, nausea and vomiting
  • If just flank pain and tenderness, may be referred from cystitis
• 30-50% of women with ‘cystitis’ actually have subclinical kidney infection

Uncomplicated UTI

• UTI
  • Without structural or functional abnormalities
  • Without relevant comorbidities that increase risk of adverse outcome
  • Not associated with GU tract instrumentation
• Diagnostic standard is culture >10^5 CFU/mL although can accept >1000 CFU/mL if symptomatic

Complicated UTI

• UTI with
  • Functional or anatomical abnormal urinary tract
    • IDC, ureteral stent, nephrolithiasis, neurogenic bladder, polycystic kidney disease, recent instrumentation
  • Presence of comorbidities that increase risk of adverse outcome
    • Male, recurrent UTI (3 or more per year), advanced age in men (prostatism, instrumentation), NH resident, neonates, DM, sickle cell, pregnancy, immunosuppression, advanced neurological disease, non-E. coli infections, known or suspected resistance
• Diagnostic standard is culture >10^5 CFU/mL
• More likely to have resistant organisms

Asymptomatic bacteriuria

• >10^5CFU/mL of a single bacterial species on two successive urine cultures without symptoms
  • Two samples rules out transient colonisation
• Occurs in 30% of pregnant women and 40% of female NH residents
• Also common in IDC and disorders that prevent complete bladder emptying
• 5% in healthy young women
• Screening only warranted in pregnant women and those undergoing urological procedures
• In pregnancy, associated with preterm labour, perinatal mortality, pyelonephritis and maternal anaemia

Asymptomatic bacteriuria (Burkett et al.)

• Definition: >10^5 CFU/mL from individual with no typical symptoms or signs of urinary system disease
• Also associated with pyuria to the same degree is UTI
• Prevalence in older persons
  • Community-dwelling: Females 6-16% and Males 4-7%
  • RACF: Females 25-55% and males 15-37%
  • IDC: 98% overall
    • Therefore only culture if fever, costovertebral, rigors or ALOC
• The most important step is assessing for signs of urinary tract infection before ordering a urine MCS as once ordered and bacteria found, treatment is almost universal

Establishing pre-test probability

• Features on past history
  • PMHX – Immunocompromise, DM, cognitive impairment, immobility, impairment in ADL’s
  • Past urology – Prior antibiotic Rx for UTI, urinary incontinence, BPH, recent instrumentation, renal stones
• History and exam findings of UTI including subjective fevers/rigors
• Absence of an alternate cause for symptoms
• Delirium alone does not increase the likelihood of UTI, but should be considered in the assessment
• No routine indication for urine testing in those that present with falls without urinary symptoms
• Need to determine if dysuria is acute or chronic (e.g. BPH/atrophic vaginitis)
• If no localising or non-specific indicators of UTI do NOT test urine for infection

Algorithm (Burkett et al.)

• Clinical signs (Localising or non-localsiing AND no suspicion of infection at other site?
  • Yes -> Send for urinalysis
  • No -> No UTI
• Does patient have pyuria (>10/HPF) (note presence of bacteria is NOT the point of difference)
  • Yes -> Possible UTI
  • No -> No UTI
• Does patient need empirical treatment (localising signs OR unstable)?
  • Yes -> Treat empirically
  • No -> Monitor for deterioration and culture results for 48 hours
    • If clinical conditions deteriorate or is unchanged at 48 hours with no alternative diagnosis, treat empirically
    • If culture results negative, consider alternative diagnoses

RACF algorithm (eTG)

• No catheter
  • Acute dysuria -> Culture and treat empirically if unwell
  • No dysuria -> Assess for two or more criteria for UTI, including at least one general (fever, altered mental status)
• With Catheter
  • One or more criteria (Fever, costovertebral, rigors, altered mental status) -> Culture
  • If not -> No culture. Re-evaluate

Relapse and reinfection

• Relapse is recurrence within a month with same organism
  • = Treatment failure
• Reinfection is development of symptoms 1-6 months later after treatment
  • Usually by different enteric organism or different serotype of same organism
  • More likely represent defect in host defence
  • If >3 in one year, evaluation for structural abnormality, tumor, calculi or immunosuppression/DM is warranted

Organisms

• E. coli >80%
• Klebsiella, Proteus, Enterobacter, Pseudomonas – 5-20%
  • Pseudomonas is a low virulence organism in urinary tract so suggests impaired host defences
• Group D strep, Chlamydia trachomatis, S. saprophyticus, M. tuberculosis – <5%

Potential complications

• Pyelonephritis
  • Diffusely enlarged kidney with perinephric stranding but without focal renal changes
• Acute bacterial nephritis
  • Ill-defined focal areas, sometimes striated or wedge-shaped, of decreased density on USS or CT
• Renal abscess
  • Well-defined areas of decreased density on CT or USS
• Emphysematous pyelonephritis
  • 70-90% of patients diabetic with gas-forming organism
  • Appear toxic and septic

Clinical presentation

• 4 specific symptoms and one sign independently increase probability of UTI
  • Dysuria
  • Frequency
  • Visible haematuria
  • Fever
  • CVA tenderness
• Self-diagnosis also increases likelihood (50-60% of women with dysuria have bacteriuria)
• Absence of vaginal discharge, pruritis increases likelihood of UTI
• Dysuria
  • Internal dysuria (burning suprapubic pain accompanied by bladder tenderness) is more specific
  • External dysuria is more specific for vaginitis, cervicitis or PID than UTI

Who needs urine testing?

• If symptomatic, can treat empirically
• Urine samples for cultures are required if:
  • Pregnany
  • Male
  • Aged care residents
  • Recent antibiotics
  • Failed oral therapy
  • Recurrent infection
  • Recent international travel in last 6 months
  • Complicated UTI/pyelonephritis

Specimen collection

• Ideally clean-catch MSU
• If immobilised, cannot provide, too unwell or extremely obese consider in/out catheter
  • 1-2% rate of UTI after single catheterisation
  • 3-8% per day rate of bacteriuria with catheterisation
• Visual inspection and odor are not helpful

Urine dipstick

• Nitrite reaction
  • >90% specific but only 50% sensitive
  • E. coli converts nitrates to nitrite
  • Enterococcus, Pseudomonas, Acinetobacter do NOT convert nitrates to nitrites
• Leukocyte esterase
  • Sensitivity 77% and specificity 54% (using culture >10^5CFU/HPF as gold standard)
  • Supports diagnosis but does not exclude it

Urine microscopy

• WCC >10/HPF in patient with symptoms is abnormal
• Lower degrees of pyuria with/without bacteriuria may still be clinically significant in the presence of symptoms
  • False negative pyuria may occur due to large fluid intake, systemic leukopaenia, self-medication with partially treated UTI
  • Pyuria may be intermittent or absent if obstructed and infected kidney
• In men, WCC >1-2/HPF is significant when bacteriuria evident

Urine microscopy

• >1 bacterium/HPF is 95% sensitive and >60% specific for culture with >10000 CFU/mL
• Contaminated samples lead to false positives

Urine culture

• If typical symptoms of cystitis or uncomplicated UTI
  • If positive leukocyte esterase, positive nitrite reaction or leukocytes on microscopy – urine culture not required
    • Most patients will respond to empirical therapy
• Perform culture for:
  • Complicated UTI
  • Pregnant women
  • Children
  • Adult males
  • Patients with relapse or reinfection
• If asymptomatic, need 2-3 positive culture results to warrant treatment (unless pregnant when treatment of asymptomatic bacteriuria is always justified)

Blood culture

• Positive in 29% of cases admitted for pyelonephritis
• Do not alter management

Imaging

• Male, elderly, diabetic, poor response to therapy or severely ill patients with acute pyelonephritis warrant imaging
• Must rule out urolithiasis
• USS can rule out hydronephrosis (but not urolithiasis directly) and image the renal parenchyma
• CT KUB can rule out urolithiasis and image the parenchyma

Algorithm (Tintinalli)

• Women with symptom/s, no risk factors for complicated infection, no back pain or fever, no vaginal discharge:
  • If history highly suggestive – 90% likelihood of UTI. Empirical Rx
  • If history not highly suggestive – perform dipstick
    • If positive – 80% likelihood of UTI. Empirical Rx
    • If negative – 20% likelihood of UTI still. Consider culture, pelvic exam and close clinical follow-up

Management

• Antibiotic resistance
  • ESBL increasing (currently 3% of community UTI isolates in Australia)
  • Consider resistant pathogen if:
    • Recent international travel in last 6 months (particularly Sth East Asia)
    • Recent antibiotic exposure
    • Non-response to oral antibiotics
    • Aged-care facility residents
  • Use alternative antibiotic if been treated with trimethoprim in last 3 months
  • In community-acquired UTI, 20% of E. coli is trimethoprim resistant and <10% are augmentin or cephalexin resistant
  • If ESBL isolated, nitrofurantoin, fosfomycin and sometimes augmentin are oral therapy options
  • If specific cardiac conditions requiring endocarditis prophylaxis, need antibiotic that covers Enterococcus

Management

• High fluid intake, complete and frequent bladder voiding may help resolve UTI
• Urinary alkalinisers help symptoms but should not be used with quinolones due to risk of crystalluria

Management

• Non-pregnant females
  • Trimethoprim 300mg nocte for 3/7
  • Cephalexin 500mg BD for 5 days
  • Augmentin 500/125 BD for 5 days
  • Nitrofurantoin 100mg BD for 5 days
  • If resistance to above confirmed – Norfloxacin 400mg BD for 3 days
• Pregnant females
  • Same as above but not trimethoprim
  • Repeat cultures 1-2 weeks after therapy to confirm resolution
  • If persistent bacteriuria, treat again

Management

• Men
  • Must perform testicular and prostate exam in all men with UTI
  • Trimethoprim 300mg daily for 7 days
  • Cephalexin 500mg BD for 7 days
  • Nitrofurantoin 100mg BD for 7 days
  • Augmentin 500/125 BD for 7 days
  • DO NOT use nitrofurantoin unless afebrile and prostatitis deemed unlikely as does not reach therapeutic concentrations in prostate
  • If resistance to all above, norfloxacin 400mg BD for 7 days
  • If prostatitis suspected, need 2-4 week course

Management

• Acute pyelonephritis
  • Imperative to take urine samples + BC before initiating empirical therapy
  • If pregnant, consider continued prophylaxis until delivery as associated with poor maternal and fetal outcomes
  • Mild infection (low fever, no nausea/vomiting)
    • Augmentin 875/125 BD for 10-14 days
    • Cephalexin 500mg q6h for 10-14 days
    • Trimethoprim 300mg daily for 10-14 days
    • If resistant to above or Pseudomonas – Cipro 500mg BD for 7 days or norfloxacin 400mg BD for 7 days
  • Repeat urine cultures at 1-2 weeks after treatment complete
• Acute pyelonephritis
  • Severe infection
    • Need imaging (USS or CT)
    • Gentamicin 5-7mg/kg IV load + Ampicillin 2g IV q6h
    • If recent travel to Sth East Asia or known ESBL – Meropenem 1g q8h
    • Total duration of therapy 10-14 days but extend to 21 days if delayed response to therapy
    • Repeat urine cultures 1-2 weeks after treatment complete

Recurrent UTI in adults

• Obtain samples for culture in all recurrence
• Treat as for pyelonephritis and ensure imaging performed
• In men, prostatitis is assumed

Prophylaxis

• Intravaginal oestrogen in post-menopausal women may reduce recurrence
• Cranberry products and hippuric acid may reduce the incidence of symptomatic UTI in women (including pregnant) and asymptomatic bacteriuria
• Consider prophylactic antibiotics if
  • Frequent symptomatic infections (2 or more within 6 months or 3 or more in 12 months)
  • Intermittent post-coital prophylaxis in pregnant women with history of UTI prior to pregnancy
  • Continuous prophylaxis in pregnant women with recurrent UTI during pregnancy
• Trimethoprim 150mg nocte, cephalexin 250mg nocte are both reasonable

UTI in NH residents

• Frequent cause of fever in NH residents
• Asymptomatic bacteriuria is very common
• Screening for and treating asymptomatic bacteriuria offers no benefit
• Mental status change is highly unlikely to be due to UTI in the absence of systemic sepsis
• If UTI considered likely, obtain sample for cultures as microbial resistance is common

UTI in NH residents

• Without IDC
  • Acute dysuria – Obtain sample
  • No dysuria
    • If 2 or more of below, with 1 of first 2, obtain sample
      • Fever, ALOC without alternative explanation, new or worsening urinary urgency, frequency, suprapubic pain/tenderness, gross haematuria, costovertebral angle tenderness, new or worsening incontinence
• With IDC
  • If 1 or more of below – Obtain sample
    • Fever, CV tenderness, rigors, ALOC without alternative explanation

UTI with IDC

• Bacteriuria and pyuria occur in most patients with IDC within days
• All symptomatic patients need urine cultures sent
• Contamination can be avoided by MSU if catheter can be removed or by collecting urine through a new catheter if able to be changed easily
• If catheter cannot be removed or changed, take sample from port drainage system rather than drainage bag, to minimise contamination
• Duration of therapy is 7 days (or 14 if delayed response)
• Must change catheter if has been in >2 weeks as antibiotic therapy usually only transiently effective as most antibiotics penetrate poorly into the biofilm
• Treatment without catheter change increases risk of superinfection with resistant bacteria
• No evidence of prophylactic antibiotics at time of catheter placement or change
  • Recommended ONLY for high-risk individuals = Unplanned urological surgery, endocarditis risk, immunosuppression

Candiduria

• Usually reflects colonisation with IDC
• Usually resolves spontaneously
• If persistent, consider renal imaging to rule out fungus balls
• In high-risk patients, may be an indicator of disseminated candidiasis
• Consider treatment in:
  • Neutropaenic
  • Patients undergoing urological manipulations
  • Symptomatic patients
• Exclude candida vulvovaginitis and balanitis
• Fluconazole 200mg orally daily for 14 days

Prostatitis

• Acute prostatitis
  • Complicated UTI that requires urological workup
  • Fever, marked acute lower UTI symptoms, perineal pain and extreme prostatic tenderness on PR
  • Can lead to abscess and bacteraemia
  • Most antibiotics have good penetration (except nitrofurantoin)
  • 2-4 week duration of usual Ab’s
  • If severe infection, treat as for severe pyelonephritis for 2-4 weeks
  • Need adequate analgesia

Prostatitis

• Chronic prostatitis
  • 90-95% of patients that present with chronic prostatitis symptoms (chronic prostate pain, recurrent lower urinary tract symptoms) have a non-infective aetiology
  • Diagnosis requires MCS of urine and expressed prostatic secretions
  • If bacterial infection confirmed, need prolonged antibiotics as relapse is common
  • Cipro 500mg BD for 4 weeks
  • Norfloxacin 400mg BD for 4 weeks
  • Trimethoprim 300mg daily for 4 weeks
  • If Ureaplasma or Chlamydia identified, doxycycline 100mg BD for 2-4 weeks

CT imaging

• Pyelonephritis appears as:
  • Hypoenhancing and hypodense renal cortex
  • Perinephric stranding
  • May just islands of this
  • Emphysematous – Gas in kidney and perinephric compartment
• Hydronephrosis
  • Increased density of calyceal fat stranding
  • Loss of calyceal fat due to swelling around it
• Nephronia
  • Focal region of interstitial nephritis and is a stepping stone to abscess formation

Last Updated on March 27, 2024 by Andrew Crofton