Urinary tract infection (lower) - women
Exam Tips
- In women <65 years, dysuria/new nocturia/cloudy urine without vaginal symptoms strongly supports lower UTI.
- Always separate lower UTI from pyelonephritis: fever, flank pain, and systemic upset imply upper tract disease and different management urgency.
- Do not diagnose UTI from cloudy or malodorous urine alone in catheterized patients; asymptomatic bacteriuria is common.
- Recurrent UTI definition to remember: at least 2 episodes in 6 months or at least 3 in 12 months.
- In prescribing stations, mention renal function check before nitrofurantoin and pregnancy status before trimethoprim.
Definition
Lower urinary tract infection (UTI) in women is an infection primarily involving the bladder (acute cystitis), usually caused by enteric bacteria ascending through the urethra. In UK practice it is classified as uncomplicated in non-pregnant women without structural/functional urinary tract abnormality or major comorbidity, and complicated when factors such as pregnancy, catheterization, obstruction, renal disease, or immunocompromise increase risk of treatment failure and ascending infection.
Pathophysiology
Most infections arise by retrograde ascent of uropathogens from periurethral/perineal flora into the bladder, where bacterial adhesins (for example, uropathogenic E. coli fimbriae) promote urothelial attachment, inflammatory cytokine release, and symptoms such as dysuria, urgency, and frequency. Less common routes are haematogenous spread (more likely in immunocompromise or obstruction) and direct inoculation during catheterization/instrumentation. Recurrent episodes may represent reinfection (new strain) or relapse (same strain persistence), and post-menopausal oestrogen deficiency contributes via mucosal and microbiome changes that reduce colonization resistance. See Figure: ascending infection pathway (urethra to bladder to kidney) in standard microbiology/urology teaching texts.
Risk Factors
- Sexual intercourse, new sexual partner, and spermicide use
- Previous UTI (including childhood UTI) and maternal family history
- Post-menopause with urogenital atrophy
- Urinary incontinence, cystocele, and raised post-void residual volume
- Urinary catheterization or recent urological instrumentation
- Structural/functional urinary tract abnormality (for example obstruction, reflux, stones, neurogenic bladder)
- Pregnancy
- Diabetes mellitus (especially poor control), immunosuppression, or renal impairment
- Healthcare exposure (hospitalization/long-term care) and recent prolonged antibiotic use
- Previous resistant UTI or travel to regions with high antimicrobial resistance
Clinical Features
Symptoms
- Dysuria (pain/burning/stinging on passing urine)
- Urinary frequency
- Urinary urgency
- New nocturia
- Suprapubic discomfort/pain
- Cloudy urine
- Visible haematuria
- In older women: new dysuria alone, or two or more of fever, urgency/frequency, new incontinence, suprapubic pain, haematuria, or new/worsening delirium
Signs
- Often no major systemic signs in uncomplicated lower UTI
- Suprapubic tenderness on abdominal examination
- Usually afebrile; fever, rigors, flank pain, or costovertebral angle tenderness suggest upper UTI/pyelonephritis instead
- Delirium in older adults should trigger broader assessment rather than automatic attribution to UTI
Investigations
Management
Lifestyle Modifications
- Maintain hydration and use simple analgesia (for example paracetamol) for symptom relief
- Provide safety-net advice: seek urgent review for fever, flank pain, vomiting, sepsis features, or non-improvement after 48 hours
- Avoid spermicides in recurrent UTI where possible; address post-void habits and contributory factors
- Do not treat asymptomatic bacteriuria in non-pregnant women (except specific indications such as pregnancy or before selected urological procedures)
Pharmacological Treatment
First-line oral antibiotic (uncomplicated lower UTI in non-pregnant women)
- Nitrofurantoin modified-release 100 mg twice daily for 3 days (or immediate-release 50 mg four times daily for 3 days)
Check renal function before prescribing; generally avoid if eGFR <45 mL/min/1.73 m2 (short-course use may be considered with caution in selected patients). Avoid in G6PD deficiency and if suspected pyelonephritis (poor tissue levels).
Alternative first-line when nitrofurantoin unsuitable and resistance risk is low
- Trimethoprim 200 mg twice daily for 3 days
Avoid in pregnancy (especially first trimester) unless specialist advice; folate antagonist. Caution with hyperkalaemia risk (for example with ACE inhibitors/ARBs/spironolactone) and with warfarin (INR interaction).
Other oral options guided by culture/local resistance
- Pivmecillinam 400 mg initial dose, then 200 mg three times daily to complete a 3-day course
- Fosfomycin trometamol 3 g single oral dose
Use according to local antimicrobial guidance and sensitivities. Pivmecillinam is contraindicated in serious penicillin hypersensitivity. Fosfomycin should not be used for suspected upper UTI; metoclopramide may reduce exposure.
Delayed or back-up prescribing strategy
- Delayed antibiotic prescription for up to 48 hours in selected mild cases with clear safety-netting
May reduce antibiotic exposure but symptom duration can be slightly longer; ensure patient understands red-flag triggers for immediate treatment/review.
Surgical / Interventional
- No surgical treatment for uncomplicated cystitis
- If catheter-associated UTI: remove or replace catheter (especially if long-standing) as part of source control
- If obstruction with infection is suspected, urgent urology referral for decompression (for example nephrostomy or stent) is required
Complications
- Persistent or recurrent infection
- Ascending infection causing acute pyelonephritis
- Renal/perinephric abscess
- Pyonephrosis in obstructed infected systems
- Acute kidney injury and potential progression to chronic kidney disease after severe/ascending infection
- Urosepsis
- Reduced quality of life (work, social, sexual functioning)
- In pregnancy: higher risk of preterm delivery, low birth weight, and maternal pyelonephritis
Prognosis
Uncomplicated lower UTI is often self-limiting, with many women improving over several days; effective susceptible antibiotics shorten symptom duration compared with no treatment or resistant therapy. A substantial minority experience recurrence, especially with prior UTI history and persistent risk factors, so recurrence prevention and antimicrobial stewardship are key in long-term management.
Sources & References
🏥BMJ Best Practice(1)
💊BNF Drug References(3)
- Cefalexin[management.pharmacological]
- Methenamine hippurate[management.pharmacological]
- Trimethoprim[management.pharmacological]
✅NICE Guidelines(1)
- Urinary tract infection (lower) - women[overview]
📖Textbook References(1)
- [Williams, Bailey and Love's Short Practice of Surgery] Norman Williams, Christopher Bulstrode, P Ronan O'Connell - Bailey & Love's Short Practice of Surgery 26E (2013, CRC Press) - libgen.li.pdf(pp. 1334, 1335)[context]