Urinary Tract Infection - Uncomplicated

Definition

Uncomplicated urinary tract infection (UTI) refers to infection of the lower urinary tract in otherwise healthy, non-pregnant adults without structural or functional abnormalities of the urinary system.

Epidemiology

• Common in adult women, especially aged 18–50 years.
• Lifetime risk in women: 50–60%; men: <10%.
• Recurrence is common, particularly in sexually active women.
• Risk factors: female anatomy, sexual activity, spermicide use, previous UTIs.
• Mostly community-acquired; rarely leads to hospitalization.

Etiology

• *Escherichia coli* is the predominant pathogen (~75–95%).
• Other pathogens: *Staphylococcus saprophyticus*, *Klebsiella*, *Proteus*, *Enterococcus* (less common).
• Transmission: ascending infection from perineal flora to urethra and bladder.
• No structural or functional urinary abnormalities.

Pathophysiology

• Bacterial colonization of periurethral area followed by ascension into bladder.
• Adherence to urothelial cells via fimbriae or adhesins.
• Local inflammatory response: neutrophil infiltration, cytokine release, bladder mucosa irritation.
• Symptoms arise primarily from bladder inflammation (cystitis).
• Usually limited to lower urinary tract; systemic involvement uncommon.