Lecture 7: Pathology of UTI's Flashcards
describe the presentation of UTI
- dysuria (pain on micturition)
- frequency
- smelly urine
- very young - unwell, failure to thrive
- very old - incontinence, off their feet
list the bacteriostatic properties of the urinary tract
- free flow of urine through normal anatomy - assumes drinking enough fluids
- low pH, high osmolality, and high ammonia (NH3) content of normal urine
- prostatic secretions are bacteriostatic
- anti-bacterial antibodies
which parts of the urinary tract are sterile?
entire urinary tract, except for terminal urethra, is sterile
why is a urine specimen for culture collected mid-stream?
Mid Stream Specimen Urine (MSSU)
initial urine is heavily contaminated with bacteria from terminal part of urethra, so collecting mid-stream avoids this contamination, however urethral flora will still be present just more diminished
when is infection indicated in a MSSU culture?
10^5 bacterial per ml usually represents infection, however 10^3-10^4 bacteria per ml could still be an infection (50% chance of infection if no symptoms)
which micro-organisms cause UTI?
- bacteria mostly = gut flora, especially E.coli
- viral infection rare
what is the usual route of UTI?
almost always ascending from distal urethra
infection in kidneys: usually infection has spread up from bladder infection > more serious
aetiology of UTI
- stasis of urine: obstruction, loss of ‘feeling’ (sensory loss) of full bladder > spinal cord/brain injury
- pushing bacteria up urethra from below: sexual activity, females, catheterisation
- generalised predisposition to infection: e.g. diabetes
consequence of obstruction of urine outflow
- proximal dilatation
- slowed urine flow > cannot flush out bacteria > infection
- slowed urine flow > sediments form > calculous (stone formation) further obstruction > more dilatation, infections and increased calculous formation
what is the most important example of urinary obstruction in children?
vesicoureteric reflux
what is vesicoureteric reflux?
- when pee moves backwards from the bladder to the kidneys.
- can be caused by decreased angulation of ureter into bladder, can also be present with hydroureter
common causes of urinary obstruction in adults
- Men: benign prostatic hyperplasia of prostate - functional and anatomical obstruction (not a tumour)
- women: uterine prolapse
- both sexes: tumours and calculi
how does a spinal cord/brain injury cause stasis of urine?
decreased sensation > no sense of when to micturate and do not know to empty bladder completely > leave urine in bladder (high residual volume) > stasis of urine.
why do females have a predisposition to UTIs?
- short urethra
- lack of prostatic bacteriostatic secretion
- closeness of urethral orifice to rectum
- sexual activity (helps if void after intercourse)
- pregnancy - pressure on ureters and bladder
why can diabetes increase risk of UTIs?
glucose in urine
poor function of WBC
what are the acute complications of UTI?
severe sepsis and septic shock
what are the chronic complications of UTI?
- chronic damage to kidneys if repeated infections (chronic pyelonephritis) > hypertension, chronic renal failure
- calculi > obstruction > hydronephrosis > hypertension, chronic renal failure