Urinary Tract Infection

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Another name for UTI


• Common in women, uncommon in men and of special importance in children.

• Recurrent infection causes considerable morbidity, if complicated can cause  severe renal disease including end-stage renal failure

• Also a common cause of life-threatening Gram-negative septicaemia


Pathogenesis:

• Infection most often due to bacteria from the patient's own bowel flora (E. coli and other coliforms = 68+%, Proteus mirabilis = 12%)

• Transfer to the urinary tract may be via the bloodstream, the lymphatics or by direct extension (e.g. a fistula).  However, most OFTEN it's via the ascending transurethral route (3 steps are needed)

  1. The lower vagina and periurethral area is heavily colonized by uropathogenic bacteria.  This is facilitated by the adhesion of bacteria to uroepithelial by pili or fimbriae present on the bacterial cell surgace.  Previous UTIs may predispose to further colonisation which may not be eliminated by treatment of the infection, causing a vicious circle.
    • Important risks for colonisation include use of a diaphragm and spermicidal jelly, hormone-deficient vaginal atrophy, and systemic antibiotic treatment for non-UTIs.  Little evidence to show that personal hygiene affects colonisation, but use of bubblebaths may contribute
  2. Bacteria are transferred along the urethra to the bladder.  This step is facilitated by sex or catheterisation.  Spontaneous transfer along the short female urethra is easy, while the longer male urethra protects against transfer of bacteria to the bladder.  Prostatic fluid also has defensive bactericidal properties.
  3. Establishment and multiplication of bacteria within the bladder.  This is the most important step.  Bladder urine is normally sterile, owing to defence mechanisms within the bladder.  These include hydrokinetic and bladder mucosal factors and constituents of urine.
    • A low flow rate, infrequent and poor bladder emptying predispose to infection.