urinary tract infection

Last edited 11/2018 and last reviewed 02/2023

Urinary tract infection (UTI) is the presence and multiplication of microorganisms in one or more structures of the urinary tract with organisms invading the surrounding tissue (1).

Infections of the urinary tract are very common accounting for 1-3% of all consultations in general practice per year (2). It is accountable for the second most common clinical indication for empirical antimicrobial therapy in primary and secondary care (3).

It is much more common in women than in men (2). Most women will have at least one urinary tract infection in their lives. It is more unusual in men (in men between 20 and 60 the incidence is less than <1%) who have longer urethras and should be investigated for underlying pathology e.g. – prostate pathology (2).

UTI includes a variety of clinical syndromes,

  • acute and chronic pyelonephritis (kidney and renal pelvis)
  • cystitis (bladder)
  • urethritis (urethra)
  • epididymitis (epididymis)
  • prostitis (prostate) (1)

The rate of incidence

  • is equal between the sexes in the first year of life
  • in elderly it is between 1 and 3 %
  • increases with age, co-existent disease or institutional care (2).

Lower UTI (3)

  • in most cases, managing lower UTI will require antibiotic treatment. However, acute, uncomplicated lower UTI in non-pregnant women can be self-limiting and for some women delaying antibiotic treatment with a back-up prescription to see if symptoms will resolve without antibiotic treatment may be an option
  • most common causative pathogen in uncomplicated UTIs is Escherichia coli (in 70 to 95% of cases). Staphylococcus saprophyticus accounts for 5 to 10% of cases and occasionally other Enterobacteriaceae, such as Proteus mirabilis and Klebsiella species are isolated
  • main complication of lower UTI is ascending infection leading to upper UTI (acute pyelonephritis)
    • most episodes of acute pyelonephritis are uncomplicated and result in no residual kidney damage - complications can include impaired renal function or renal failure, septicaemia and preterm labour in pregnancy
      • in men, prostate involvement is common, which may lead to acute prostatitis, chronic bacterial prostatitis or a prostatic abscess; urinary stones are also a possibility
      • in children, UTIs can lead to renal scarring, but more often this is preceded by acute pyelonephritis rather than lower UTI, and it is more common in children with vesicoureteral reflux

Nationally for England, resistance of E. coli (the main causative organism of lower UTIs) in laboratory-processed urine specimens to the following antibiotics is:

  • nitrofurantoin: 2.5% (varies by area from 2.0 to 3.6%)
  • trimethoprim: 30.3% (varies by area from 27.1 to 33.4%)
  • pivmecillinam: 7.5% (varies by area from 4.1 to 15.7%)
  • cefalexin: 9.9% (varies by area from 8.1 to 11.4%)

Asymptomatic bacteriuria, where there is significant bacteriuria but no symptoms or signs of infection, is not routinely screened for or treated, except if it is considered a risk factor, such as in pregnant women