Lecture 7: Pathology of UTI's

Question 1

describe the presentation of UTI

Answer 1

• dysuria (pain on micturition)
• frequency
• smelly urine
• very young - unwell, failure to thrive
• very old - incontinence, off their feet

Question 2

list the bacteriostatic properties of the urinary tract

Answer 2

• 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

Question 3

which parts of the urinary tract are sterile?

Answer 3

entire urinary tract, except for terminal urethra, is sterile

Question 4

why is a urine specimen for culture collected mid-stream?

Mid Stream Specimen Urine (MSSU)

Answer 4

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

Question 5

when is infection indicated in a MSSU culture?

Answer 5

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)

Question 6

which micro-organisms cause UTI?

Answer 6

• bacteria mostly = gut flora, especially E.coli
• viral infection rare

Question 7

what is the usual route of UTI?

Answer 7

almost always ascending from distal urethra
infection in kidneys: usually infection has spread up from bladder infection > more serious

Question 8

aetiology of UTI

Answer 8

• 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

Question 9

consequence of obstruction of urine outflow

Answer 9

• 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

Question 10

what is the most important example of urinary obstruction in children?

Answer 10

vesicoureteric reflux

Question 11

what is vesicoureteric reflux?

Answer 11

• 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

Question 12

common causes of urinary obstruction in adults

Answer 12

• Men: benign prostatic hyperplasia of prostate - functional and anatomical obstruction (not a tumour)
• women: uterine prolapse
• both sexes: tumours and calculi

Question 13

how does a spinal cord/brain injury cause stasis of urine?

Answer 13

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.

Question 14

why do females have a predisposition to UTIs?

Answer 14

• 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

Question 15

why can diabetes increase risk of UTIs?

Answer 15

glucose in urine
poor function of WBC

Question 16

what are the acute complications of UTI?

Answer 16

severe sepsis and septic shock

Question 17

what are the chronic complications of UTI?

Answer 17

• chronic damage to kidneys if repeated infections (chronic pyelonephritis) > hypertension, chronic renal failure
• calculi > obstruction > hydronephrosis > hypertension, chronic renal failure