Urinary tract infections (UTIs)

Definition
Urinary tract infections are infections of any part of the urinary system, most commonly the bladder (cystitis) and urethra (urethritis), but can also involve the kidneys (pyelonephritis) or prostate (prostatitis). They are typically caused by bacteria entering the urinary tract from the urethra and multiplying.

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Types

1. Lower UTI – cystitis, urethritis

2. Upper UTI – pyelonephritis, ureteritis

3. Complicated UTI – associated with structural or functional urinary tract abnormalities, catheters, immunosuppression

4. Uncomplicated UTI – occurs in otherwise healthy, non-pregnant women with normal urinary tract anatomy

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Causes

• Most common pathogen: Escherichia coli (70–90%)

• Others: Klebsiella pneumoniae, Proteus mirabilis, Enterococcus faecalis, Staphylococcus saprophyticus (in young women)

• Fungal UTIs (e.g., Candida) in immunocompromised or catheterised patients

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Risk Factors

• Female anatomy (shorter urethra)

• Sexual activity

• Use of spermicides or diaphragms

• Pregnancy

• Menopause (reduced estrogen)

• Urinary tract obstruction (stones, tumours)

• Catheterisation

• Diabetes mellitus

• Immunosuppression

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Clinical Features

Lower UTI (cystitis, urethritis)

• Dysuria (burning when urinating)

• Frequency and urgency

• Suprapubic discomfort

• Cloudy or foul-smelling urine

• Haematuria (sometimes)

Upper UTI (pyelonephritis)

• Fever, chills

• Flank or back pain (costovertebral angle tenderness)

• Nausea and vomiting

• Symptoms of lower UTI often present

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Diagnosis

• Urinalysis: leukocyte esterase, nitrites (for Gram-negative bacteria), pyuria, bacteriuria

• Urine culture: gold standard; ≥10⁵ CFU/mL significant in asymptomatic patients; lower counts in symptomatic patients

• Blood tests: FBC, CRP if systemic infection suspected

• Imaging: ultrasound or CT in recurrent, complicated, or atypical cases

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Treatment

A. Uncomplicated cystitis in non-pregnant women

• Nitrofurantoin 100 mg twice daily for 5 days

• Trimethoprim 200 mg twice daily for 3 days (avoid if local resistance high or during early pregnancy)

• Fosfomycin trometamol 3 g single dose

B. Complicated UTI / Pyelonephritis

• Oral or IV antibiotics based on culture and sensitivity

• Examples: co-amoxiclav, ciprofloxacin, cefalexin

• Duration: 7–14 days depending on severity

• IV therapy (e.g., ceftriaxone, gentamicin) for severe infection, then step down to oral

C. Pregnant women

• Safe options: nitrofurantoin (avoid at term), cefalexin, amoxicillin (if sensitive)

• Avoid trimethoprim in first trimester and quinolones throughout pregnancy

D. Catheter-associated UTI

• Remove or replace catheter

• Antibiotic therapy guided by culture

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Prevention

• Adequate hydration

• Urinate after sexual intercourse

• Wipe front to back after toileting

• Avoid unnecessary catheterisation

• In recurrent UTIs:

• Low-dose prophylactic antibiotics in selected patients

• Vaginal estrogen in postmenopausal women

• Behavioural modifications (avoid spermicides, maintain hydration)