Pathophysiology
Clinical meaning
Women are disproportionately affected by UTI due to anatomic, hormonal, and microbiological factors. The female urethra (3-4 cm) provides a short conduit for uropathogenic bacteria to ascend from the periurethral area to the bladder. The proximity of the urethral meatus to the vaginal introitus and rectum facilitates colonization with fecal flora, particularly E. coli. Recurrent UTI, defined as >=3 culture-confirmed episodes in 12 months or >=2 episodes in 6 months, affects approximately 27% of women who experience an initial UTI, with recurrence within 6 months in most cases. The pathogenesis of recurrence involves two mechanisms: reinfection (new episode with different strain or same strain re-acquired from fecal reservoir, accounting for ~80% of recurrences) and relapse (persistence of the same organism in a sequestered focus, such as intracellular bacterial communities in the bladder urothelium or renal parenchyma). Genetic factors influence susceptibility: women who are non-secretors of ABO blood group antigens (lacking the FUT2 gene) have increased vaginal epithelial cell receptor expression for uropathogenic E. coli, approximately doubling their recurrence risk. In postmenopausal women, declining estrogen levels cause profound changes in the...