Key Facts

UTI is one of the most frequently encountered infections in primary care. Most are uncomplicated lower UTIs in women that respond well to empirical antibiotic therapy. Recognition of complicated UTI, upper tract involvement, and appropriate investigation of atypical presentations is essential.

Epidemiology

• Lifetime risk in women: approximately 50%; 27% will have at least one recurrence within 6 months
• Male UTI is less common and should prompt investigation for underlying cause
• Peak incidence in young sexually active women and postmenopausal women
• UTI in pregnancy: 2-10% develop asymptomatic bacteriuria; untreated, 30-40% progress to pyelonephritis

Aetiology

• E. coli: 70-90% of uncomplicated community-acquired UTI
• Staphylococcus saprophyticus: 5-15%, particularly in young women
• Klebsiella, Proteus, Enterococcus: together account for 5-10%
• Proteus mirabilis: more common in men and with urinary catheters; associated with struvite stones
• Risk factors: female sex, sexual activity, pregnancy, menopause (vaginal atrophy), diabetes, urinary catheterisation, urinary tract abnormalities, immunosuppression

Pathophysiology

• Ascending infection: uropathogens colonise the periurethral area, ascend the urethra, and adhere to urothelial cells via fimbriae (type 1 and P fimbriae)
• Shorter female urethra (4 cm vs 20 cm in males) explains higher female prevalence
• Virulence factors of E. coli (adhesins, toxins, siderophores) promote colonisation and invasion
• Complicated UTI involves structural or functional abnormalities impairing urinary flow or host defences

Uncomplicated Lower UTI (Cystitis)

• Dysuria (burning on micturition)
• Frequency and urgency
• Suprapubic pain or discomfort
• Haematuria (visible or non-visible)
• Cloudy or malodorous urine
• No systemic symptoms

Upper UTI (Pyelonephritis)

• Loin/flank pain (unilateral or bilateral)
• Fever ≥38°C, rigors
• Nausea and vomiting
• Costovertebral angle tenderness
• May have lower urinary tract symptoms

UTI in the Elderly

• May present atypically: confusion, falls, functional decline
• Avoid attributing non-specific symptoms to UTI on dipstick alone (asymptomatic bacteriuria is common)

Red Flags

• Signs of sepsis: fever >38°C, tachycardia, hypotension, altered mental state
• Loin pain with systemic symptoms — pyelonephritis
• Visible haematuria in patients >45 years — requires 2-week-wait urology referral to exclude malignancy
• UTI in men — investigate for underlying cause
• Recurrent UTI — consider investigation for structural abnormality
• UTI in pregnancy — risk of pyelonephritis and preterm labour

Bedside

• Urine dipstick: nitrites (high specificity >90%, sensitivity 50-70%), leucocyte esterase (high sensitivity, lower specificity), blood
• Observations: temperature, HR, BP (sepsis screen)
• In women <65 with ≥2 of dysuria, frequency, urgency: treat empirically without dipstick (NICE NG109)

Bloods

• Not required for uncomplicated lower UTI
• FBC, CRP, U&Es, blood cultures if pyelonephritis or sepsis suspected

Microbiology

• MSU for culture and sensitivity: not required for uncomplicated lower UTI in young women
• MSU recommended for: men, pregnant women, children, recurrent UTI, treatment failure, atypical symptoms, catheter-related UTI
• Significant bacteriuria: ≥10⁵ CFU/mL (some labs use ≥10³ for symptomatic patients)

Imaging

• Not required for uncomplicated UTI
• USS renal tract: if recurrent UTI, male UTI, suspected complications (abscess, obstruction)
• CT urogram: if haematuria persisting after UTI treatment or structural abnormality suspected

Special Tests

• Residual urine assessment if voiding dysfunction suspected
• Urodynamics if recurrent UTI with voiding symptoms
• Cystoscopy for recurrent UTI in patients >45 or with risk factors for malignancy

Non-pharmacological

• Adequate fluid intake (aim 2-3 L/day during acute infection)
• Paracetamol or ibuprofen for pain/fever
• Voiding habits: regular voiding, post-coital voiding
• Cranberry products: limited evidence; NICE does not recommend for prevention
• Vaginal oestrogen for postmenopausal women with recurrent UTI (reduces recurrence by 50%)

Pharmacological

Uncomplicated lower UTI in non-pregnant women (NICE NG109):

• First-line: nitrofurantoin 100mg MR BD for 3 days (avoid if eGFR <45 mL/min)
• Second-line: trimethoprim 200mg BD for 3 days (avoid if used in preceding 3 months or local resistance >30%)
• Third-line: pivmecillinam 400mg initial dose then 200mg TDS for 3 days; or fosfomycin 3g single dose

Lower UTI in men:

• Trimethoprim 200mg BD for 7 days or nitrofurantoin 100mg MR BD for 7 days

UTI in pregnancy:

• First-line: nitrofurantoin 100mg MR BD for 7 days (avoid at term — risk of neonatal haemolysis)
• Alternative: amoxicillin 500mg TDS for 7 days (if culture-sensitive); cefalexin 500mg BD for 7 days
• Treat asymptomatic bacteriuria in pregnancy

Acute pyelonephritis (managed in community if mild):

• Cefalexin 500mg BD-TDS for 7-10 days or co-amoxiclav 500/125mg TDS for 7-10 days
• Hospital admission if systemically unwell, unable to take oral medication, pregnant

Recurrent UTI prophylaxis:

• Self-start antibiotic courses for women with ≥3 UTIs/year
• Low-dose prophylaxis: nitrofurantoin 50-100mg nocte or trimethoprim 100mg nocte for 6 months
• Vaginal oestrogen in postmenopausal women
• D-mannose 2g daily (some evidence of benefit)

Surgical

• Not generally applicable unless structural abnormality requiring correction

Referral Criteria

• Male UTI: urology referral for investigation of underlying cause
• Visible haematuria >45 years: 2-week-wait urology referral
• Recurrent UTI not responding to prophylaxis: urology or urogynaecology referral
• Complicated UTI with suspected structural abnormality
• Pyelonephritis in pregnancy: hospital admission

• Uncomplicated UTI: 90-95% resolution with appropriate antibiotics; symptom improvement within 24-48 hours
• Recurrence: 27% recur within 6 months; 44-70% within 1 year
• Pyelonephritis: full recovery in >90% with appropriate treatment; <5% develop complications (perinephric abscess, sepsis)
• UTI in pregnancy: untreated asymptomatic bacteriuria leads to pyelonephritis in 30-40%; associated with preterm birth and low birth weight
• Antimicrobial resistance: trimethoprim resistance in E. coli approximately 30% in UK; nitrofurantoin resistance <5%

NICE NG109 Treatment Summary

Dipstick Interpretation