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Diagnosis of urinary tract infections (UTIs)

Urinary symptoms in adult women <65 years

  • Do not culture routinely
  • In sexually active young people with urinary symptoms, consider Chlamydia trachomatis

Algorithm for the assessment of urinary symptoms in adult women <65 years

Algorithm for the assessment of urinary symptoms in women (65 years of age 1280x1036

Urine culture in women and men >65 years

  • Do not send urine for culture in asymptomatic elderly with positive dipsticks
  • Only send urine for culture if two or more signs of infection, especially dysuria, fever >38°C, or new incontinence
  • Do not treat asymptomatic bacteriuria in the elderly as it is very common
  • Treating does not reduce mortality or prevent symptomatic episodes, but does increase side-effects and antibiotic resistance

Urine culture in women and men with catheters

  • Do not treat asymptomatic bacteriuria in those with indwelling catheters, as bacteriuria is very common, and antibiotics increase side-effects and antibiotic resistance
  • Treatment does not reduce mortality or prevent symptomatic episodes, but does increase side-effects and antibiotic resistance
  • Only send urine for culture in catheterised if features of systemic infection. However, always:
    • exclude other sources of infection
    • check that the catheter drains correctly and is not blocked
    • consider need for continued catheterisation
    • if the catheter has been in place for more than seven days, consider changing it before/when starting antibiotic treatment
  • Do not give antibiotic prophylaxis for catheter changes unless history of symptomatic UTIs due to catheter change

When else should I send a urine for culture?

  • Pregnancy: if symptomatic for investigation of positive UTI, and at first antenatal visit, as asymptomatic bacteriuria associated with pyelonephritis and premature delivery
  • Suspected pyelonephritis (loin pain and fever)
  • Suspected UTI in men
  • Failed antibiotic treatment or persistent symptoms
    • E. coli with ESBL and CPE enzymes are increasing in the community
    • ESBLs are multi-resistant, but usually remain sensitive to nitrofurantoin or fosfomycin
  • Recurrent UTI, abnormalities of genitourinary tract, or renal impairment, as more likely to have a resistant strain

Sampling in women and men

  • Refrigerate specimens to prevent bacterial overgrowth, or use specimen pots with boric acid (fill to the line)
  • Women: specimen should be midstream. Cleansing with water and holding the labia apart are not essential. Cleansing with antiseptic leads to false negatives
  • Men: specimen should be midstream
  • People with catheters: using aseptic technique, drain a few ml of urine, then collect a sample from catheter sampling port

How do I interpret a culture result?

  • Usually indicates UTI in patient with urinary symptoms. Higher counts have even higher positive predictive value
    • single organism >104 colony forming units (CFU)/ml
    • >105 mixed growth with one predominant organism
    • Escherichia coli or Staphylococcus saprophyticus >103 CFU/ml
  • Do not treat asymptomatic bacteriuria in the elderly as it does not reduce mortality or prevent symptomatic episodes
  • White blood cells:
    • white cells >104/ml are considered to represent inflammation
    • ‘no white cells present’ indicates no inflammation and reduces culture significance
    • pregnancy is associated with physiological pyuria
  • Sterile pyuria:
    • in sterile pyuria, consider Chlamydia trachomatis (especially if 16–24 years), other vaginal infections, other non-culturable organisms, including TB or renal pathology
  • Epithelial cells/mixed growth:
    • presence indicates perineal contamination, which reduces significance of culture
  • Red cells:
    • may be present in UTI; refer patients with persistent haematuria post-UTI
    • lab microscopy for red cells is less accurate than dipstick due to red cell lysis in transport

Is a follow-up urine sample needed?

  • Follow-up urine samples are not usually indicated, except when treating asymptomatic bacteriuria in pregnancy

Children

  • Consider UTI in any sick child and every young child with unexplained fever

Algorithm for the assessment of urinary symptoms in children

Algorithm for the assessment of urinary symptoms in children 1280x1178

  • Sampling in children:
    • in toddlers, clean catch urine using potties washed in hot water (60°C) with washing up liquid are suitable
    • in infants, clean catch urine is preferable; a collection pad in a nappy may be used but is less accurate; changing the pad every 30 minutes until urine is passed reduces contamination; bag urines are less comfortable
  • Interpretation of culture results:
    • single organism >104 CFU/ml indicates UTI; suprapubic aspirates: growth is significant
    • all children need clinical assessment for risk factors; if risk factors or non E. coli UTI, renal imaging needed
    • white blood cells: in children, pyuria may be absent, or present (due to fever without UTI)

full guideline available from…

www.gov.uk/government/publications/urinary-tract-infection-diagnosis

Public Health England. Diagnosis of urinary tract infections (UTIs). Updated June 2017.

First included: July 2017.