Differential Diagnosis

Common Diagnoses

Rare Diagnoses

  • Bladder Tumour
  • Behcet’s Syndrome
  • Schistosomiasis
  • Tuberculosis
  • Benign Prostatic Hypertrophy/Overactive Bladder (Common Problems but Rarely Present with Dysuria)
  • Endometriosis
  • Ketamine-Associated Ulcerative Cystitis

Ready Reckoner

Key distinguishing features of the most common diagnoses

Lower UTIUpper UTISTIPeri-Urethral InflammationPainful Bladder Syndrome
Systemic UpsetNoYesNoNoNo
Recurring ProblemPossiblePossibleNoPossibleYes
MSU PositivePossiblePossibleNoNoNo
Vaginal/Urethral DischargeNoNoPossiblePossibleNo
Visible External AbnormalityNoNoPossibleYesNo

Possible Investigations

Likely:Urinalysis, MSU, swabs and other investigations for STI.

Possible:Vulval/vaginal swab (for non-STI causes), cystoscopy and abdominal ultrasound, hospital based urological investigations, gynaecological investigations.

Small Print:FBC, ESR/CRP, EMU, serological testing.

  • Urinalysis: If nitrite positive, very likely UTI, if only leucocytes positive probable UTI, but if nitrite and leucocyte negative UTI very unlikely; UTI may also cause proteinuria and haematuria; positive findings in various other scenarios (e.g. leucocytes positive in STI, TB, peri-urethral inflammation, blood positive in stone and tumour).
  • MSU: To confirm any suspected infection; sterile pyuria in STI, TB, peri-urethral inflammation; microscopy may reveal schistosomiasis eggs.
  • STI investigations: In suspected STI, usually arranged in local GUM clinic
  • Other vulval/vaginal swab: In the presence of a discharge when STI not suspected (e.g. to confirm thrush).
  • Cystoscopy and ultrasound: May be necessary in recurrent UTI to exclude any underlying problem, or in persistent or recurrent dysuria when the diagnosis is unclear (may reveal, for example, bladder stone, enlarged prostate or bladder tumour).
  • Hospital based urological investigations (e.g. for young children with recurrent or severe UTI).
  • FBC, ESR/CRP: Raised white cell count and inflammatory markers in acute prostatitis; eosinophilia in schistosomiasis.
  • EMU: Three EMUs for microscopy and culture for suspected TB.
  • Serological testing: For suspected schistosomiasis.
  • Gynaecological investigations: Usually in secondary care, if endometriosis suspected.

Top Tips

  • In a clear case of lower UTI in women under 65, it is reasonable to make the diagnosis – with appropriate safety netting – without urinalysis or MSU.
  • Remember peri-urethral inflammation as a potential cause. This is particularly common in children who are often presented as ‘another water infection’ when, in fact, they have balanitis or vulvitis.
  • A ‘negative’ (for growth) MSU packed with pus cells is not ‘normal’. There are many possible explanations, including STI, peri-urethral inflammation and TB.
  • Re-test the urine after treatment of lower UTI if there is visible or non-visible haematuria, and consider further investigations if the haematuria persists.
  • Acute prostatitis is probably under-diagnosed. Suspect it if a man presents with UTI-type features plus sudden onset of obstructive urinary symptoms and systemic upset. If managed in the community, these men require two weeks of antibiotic.

Red Flags

  • Take care when triaging – pressure of work may mean a rushed assessment. Remember that dysuria might be just one part of an acute pyelonephritis, so enquire specifically about fever, rigors and systemic upset. These patients will need to be seen and may need admission.
  • Remember that recurrent lower UTIs occasionally have an underlying cause. In particular, beware the older patient with little or no previous history of UTIs suddenly experiencing recurrent or persistent problems – there could be an underlying bladder tumour.
  • Do not overlook the possibility of an STI which is commonest in, though not restricted to, the younger age groups. Ask about this possibility, other relevant symptoms, and sexual history.
  • Remember to investigate children with recurrent or severe UTI according to prevailing guidance.
  • Bear in mind that unexplained dysuria in children may occasionally be a sign of abuse.
  • UTIs are much less common in men – refer for investigation if recurrent.
  • Remember the possibility of chronic ketamine abuse in young people.
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