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Summary for primary care

Diagnosis of Urinary Tract Infections: Quick Reference Tool

PHE

Overview

The aim of this Guidelines summary is to provide a simple, effective, economical, and empirical approach to the diagnosis of urinary tract infections (UTIs) and minimise the emergence of antibiotic resistance in the community.

The quick reference tool has been produced in consultation with general practitioners, nurses, specialists, and patient representatives. 

The tool is in agreement with other publications, including NICE Clinical Knowledge Summaries (CKS) and Scottish Intercollegiate Guidelines Network (SIGN). 

NICE has endorsed that this quick reference tool accurately reflects recommendations in the NICE guideline on antimicrobial stewardship and urinary tract infections.

The quick reference tool is fully referenced and graded. 

The quick reference tool is not all-encompassing, as it is meant to be ‘quick reference’. Clinicians should ultimately rely on their clinical judgement and use with other recommended resources. If more detail is required, referral to the websites and references cited is suggested. 

All Patients

Algorithm 1: Flowchart for Women (Under 65 Years) with Suspected UTI

  • Excludes women with recurrent UTI (two episodes in last 6 months, or three episodes in last 12 months) or urinary catheter.
Algorithm 1: Flowchart for Women (Under 65 years) with Suspected UTI
Guidelines summaries of NICE/PHE antimicrobial prescribing guidance are available:

Diagnostic Points for Men Under 65 Years

  • Asymptomatic bacteriuria is rare in men <65 years.

Consider Other Genitourinary Causes of Urinary Symptoms

  • If sexually active, check sexual history for sexually transmitted infections (STIs), for example chlamydia and gonorrhoea
  • Urethritis due to urethral inflammation post-sexual intercourse, irritants, or STIs.

Check for Pyelonephritis, Prostatitis, Systemic Infection, or Suspected Sepsis Using Local Policy

  • Urinary symptoms with fever or systemic symptoms in men are strongly suggestive of prostatic involvement or pyelonephritis
  • Acute prostatitis may present with feverish illness of sudden onset, symptoms of prostatitis (low back, suprapubic, perineal, or sometimes rectal pain), symptoms of UTI (dysuria, frequency, urgency or retention), or exquisitely tender prostate on rectal examination
  • Recurrent or relapsing UTI in men should prompt referral to urology for investigation.

Diagnostic Points in Men

  • To confirm diagnosis, always send a mid-stream urine sample for culture, collected before antibiotics are given
  • Do not use urine dipsticks to rule out infection as they are unreliable for this
  • A urine dipstick test with positive nitrites makes UTI more likely in men (PPV 96%). Negative for both nitrite and leucocyte makes UTI less likely, especially if symptoms are mild
  • If suspected UTI, offer immediate treatment according to NICE/PHE guideline on lower UTI: antimicrobial prescribing and review choice of antibiotic with pre-treatment culture results.

Algorithm 2: Flowchart for Suspected UTI in Catheterised Adults or Those Over 65 Years

Algorithm 2: Flowchart for Suspected UTI in Catheterised Adults or Those Over 65 Years

Guidelines summaries of NICE/PHE antimicrobial prescribing guidance are available:

Sending Urine for Culture and Interpreting Results in All Adults

  • Review need for culture when considering treatment
  • Send a urine for culture in:
    • over 65 year olds if symptomatic and antibiotic given
    • pregnancy: for routine antenatal tests, or if symptomatic
    • suspected pyelonephritis or sepsis
    • suspected UTI in men
    • failed antibiotic treatment or persistent symptoms
    • recurrent UTI (two episodes in 6 months or three in 12 months)
    • if prescribing antibiotic in someone with a urinary catheter
    • as advised by local microbiologist
  • Consider risk factors for resistance and send urine for culture if:
    • abnormalities of genitourinary tract
    • renal impairment
    • care home resident
    • hospitalisation for >7 days in last 6 months
    • recent travel to a country with increased resistance
    • previous UTI resistant
  • If prescribing an antibiotic, review choice when culture and antibiotic susceptibility results are available.

Sampling in All Men and Women

  • Women: mid-stream urine (NHS Choices) and holding the labia apart may help reduce contamination but if not done, sample can still be sent for culture. Do not cleanse with antiseptic, as bacteria may be inhibited
  • Elderly/frail: only take urine sample if symptomatic and able to collect good sample. If incontinent, clean catch in disinfected container and condom catheters for men may be viable options but little evidence to support
  • Men:  advise on how to take a mid-stream specimen (NHS Choices)
  • People with urinary catheters: collect from newly placed catheter using aseptic technique if changed, drain a few millilitres of residual urine from the tubing before using sampling port, then collect a fresh sample from catheter sampling port.
Culture urine within 4 hours of collection, refrigerate, or use boric acid preservative. Boric acid can cause false negative culture if urine not filled to correct mark on specimen bottle and can affect urine dipstick tests.

How Do I Interpret a Urine Culture Result if I Suspect a UTI?

  • Culture should be interpreted in parallel to severity of signs/symptoms. False negatives/positives can occur
  • Do not treat asymptomatic bacteriuria unless pregnant as it does not reduce mortality or morbidity
  • Urine culture results in patients with urinary symptoms that usually indicate UTI:
    • many labs use growth of 107–108 cfu/l (104–105  cfu/ml) to indicate UTI
    • lower counts can also indicate UTI if patient symptomatic:
      • strongly symptomatic women—single isolate ≥105 cfu/l (≥102 cfu/ml) in voided urine
      • in men, counts as low as 106 cfu/l (103 cfu/ml) of a pure or predominant organism
      • any single organism ≥107 cfu/l (≥104 cfu/ml)
      • Escherichia coli or Staphylococcus saprophyticus ≥106 cfu/l (≥103 cfu/ml)
      • ≥108 cfu/l (≥105 cfu/ml) mixed growth with one dominant organism
  • Epithelial cells/mixed growth:
    • the presence of epithelial cells is not necessarily an indicator of perineal contamination, culture result should be interpreted with symptoms and repeated if significance is uncertain
    • mixed growth may indicate perineal contamination; however a small proportion of UTIs may be due to genuine mixed infection. Consider a re-test if symptomatic
  • Red cells:
    • may be present in UTI
    • chemical tests may be more sensitive than microscopy as a result of the detection of haemoglobin released by haemolysis
    • refer patients with persistent haematuria post-UTI to urology
  • White blood cells (WBC)/leucocytes:
    • white cells ≥107 WBC/l (≥104 WBC/ml) are considered to represent inflammation in urinary tract, this includes the urethra
    • white cells can be present in older people with asymptomatic bacteriuria, as the immune system does not differentiate colonisation from infection
  • Sterile pyuria
    • in sterile pyuria, consider Chlamydia trachomatis (especially if 16–24 years), other vaginal infections, other nonculturable organisms including tuberculosis or renal pathology
    • if recurrent pyuria with UTI symptoms, discuss with local microbiologist as lower counts down to 105 cfu/l (102 cfu/ml) may be significant. Higher volume of urine may need to be cultured, including for fastidious organisms.
Follow up:For all patients: consider antibiotic susceptibility results and resistance when deciding on management and reviewing antibiotic treatment.

Please refer to joint NICE/PHE guidance: NICE/PHE guidelines on UTI (lower): antimicrobial prescribing or NICE/PHE guidelines on pyelonephritis (acute): antimicrobial prescribing or NICE/PHE guideline on catheter-associated UTI: antimicrobial prescribing.

Algorithm 3: Flowchart for Infants/Children Under 16 years with Suspected UTI

  • Consider UTI in any sick child and every young child with unexplained fever.
Algorithm 3: Flowchart for Infants/Children Under 16 Years with Suspected UTI

Guidelines summaries of NICE/PHE antimicrobial prescribing guidance are available:

Key Points for Infants/Children Under 16 Years with Suspected UTI

Sampling in Children:

  • If sending a urine culture, obtain sample before starting antibiotics
  • If child has alternative site of infection do not test urine unless remains unwell—then test within 24 hours
  • In infants/toddlers, clean catch urine advised; gentle suprapubic cutaneous stimulation using gauze soaked in cold fluid helps trigger voiding; clean catch urine using potties cleaned in hot water with washing up liquid; nappy pads cause more contamination, and parents find bags more distressing
  • If non-invasive not possible consider: catheter sample, or suprapubic aspirate (with ultrasound guidance)
  • Culture urine within 4 hours of collection, if this is not possible refrigerate, or use boric acid preservative. Boric acid can cause false negative culture if urine not filled to correct mark on specimen bottle.

Interpretation of Culture Results in Children:

  • Single organism ≥106 cfu/l (103 cfu/ml) may indicate UTI in voided urine
  • Any growth from a suprapubic aspirate is significant
  • Pyuria ≥107 WBC/l (104 WBC/ml) usually indicate UTI, especially with clinical symptoms but may be absent.

Other Diagnostic Tests

  • Do not use CRP to differentiate upper UTI from lower UTI.

Ultrasound

  • If proven UTI is atypical (seriously ill, poor urine flow, abdominal or bladder mass, raised creatinine, septicaemia, failure to respond to antibiotic within 48 hours, non-E.coli infection): ultrasound all children in acute phase and undertake renal imaging within 4–6 months if under 3 years
  • All ages with recurrent UTI
  • For children under 6 months or those with non-E.coli UTI: ultrasound within 6 weeks if UTI not atypical and responding to antibiotics
  • Refer to NICE CG54 for other things to consider in suspected UTI in children.

References

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