Urinary Tract Infection (lower)

Usually describes acute urethritis and cystitis caused by a microorganism.


  • Common- accounts for around 1-3% of consultations in GP; affects around 3% of women at age 20 and increasing by ~1% every decade.
    • In men, UTI is uncommon except in neonates/infants and in men >60 with LUTS.


  • More common in women because, the urethra is shorter and there is closer proximity between the urethra and the vagina and anus.
  • Patients with catheters (or other instrumentation or foreign bodies- technically including renal stones) are also much higher risk
  • Bladder outflow obstruction e.g. BPH, Prostate Cancer, urethral stricture
  • Uterine prolapse
  • Neurological conditions e.g. MS, diabetic neuropathy
  • Diabetes mellitus
  • NB Have a high clinical suspicion in elderly people (particularly females) who have acute onset fever or delirium of unknown cause, as this is the most common cause.


  • The most common organisms to cause UTIs are
    • E coli (from the GI tract- account for ~75%)
    • Proteus spp
    • Staphylococcus saprophyticus
    • Other organisms include
      • Pseudomonas spp, streptococci and staph epidermidis
      • In hospital, Klebsiella and streptococci are more common (E coli still most common)
  • Entry of the organisms may be retrograde (via the urethra), via the bloodstream (particularly in immunosuppressed) or direct (via instrumentation)

Clinical Presentation

  • abrupt onset frequency and urgency of micturition
  • scalding/burning pain (dysuria) in the urethra during micturition
  • suprapubic pain during and after voiding
  • feeling of incomplete emptying (due to spasm of the inflamed bladder wall)
  • cloudy urine which may have an offensive smell
  • there may also be haematuria
  • Systemic symptoms e.g. fever, rigors, nausea/vomiting, confusion etc are usually only mild in simple UTI.  If these signs are present, suspect pyelonephritis and/or bacteraemia.
  • Make sure to ask about previous UTIs and PMHx


  • NB UTI in females is a clinical diagnosis and investigations aren’t completely necessary.  UTI in males should be investigated with culture (male UTI is often immediately classed as complicated)
  • Urinalysis
    • Leucocytes and nitrites are suggestive of UTI
  • Urine microscopy/culture & sensitivity
  • In some cases, particularly if the patient is having recurrent episodes or if there is a history suspicious of renal stones, USS imaging may be of benefit.


  • In uncatheterised patients
    • 1st line- Trimethoprim 200mg BD for 3 days (female- unless pregnancy is suspected/known) or 7 days (male) OR Nitrofurantoin MR 100mg BD or 50mg QDS for 3 or 7 days.
    • 2nd line- culture sample and treat as sensitivities

Special cases

  • Patients with chronic kidney disease
    • In patients with CKD 3B/4/5, consider pivmecillinam (400mg stat then 200mg TDS for 3 days)
  • UTI in pregnancy
    • 1st line nitrofurantoin MR 100mg BD or 50mg QDS for 7 days in the 1st and 2nd trimester
      • In the 3rd trimester, trimethoprim 200mg BD for 7 days
    • 2nd line cefalexin 500mg every 8 hours for a minimum of 7 days or as per sensitivities
  • Recurrent UTIs in women (≥2/month or ≥3/year)
    • Treat for 6 months then review
    • 100mg trimethoprim at night/post-coital OR nitrofurantoin 50-100mg at night/post-coital
      • (Cranberry juice/extract also has evidence)
  • Catheterised patients
    • In the presence of a catheter, antibiotics will NOT eradicate bacteria
    • Change catheter prior to treatment
    • Send sample
    • Treat only if symptomatic/systemically unwell
    • If in the community
      • Co-amoxiclav 625mg TDS for 14 days or cotrimoxazole 960mg BD for 14 days
        • 2nd line, base on sensitivities
    • If in hospital
      • IV Amoxicillin and Gentamicin (cotrimoxazole + gentamicin)
        • Aztreonam can be used as an alternative to gentamicin in patients with kidney failure (AKI/CKD)
        • Step down to co-trimoxazole or adjust as sensitivities suggest for 14 days total

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