9. UTIs Flashcards
What factors play a role in the pathogenesis of a UTI?
Innoculum size Virulence of organism Host factors Tract abnormalities Age
What host factors can predispose to a UTI?
Incomplete bladder emptying Low water intake Integrity of the vesicle-uretal valve Length of the ureter Lactobacillus is protective in young women
What tract abnormalities can predispose to UTI?
Obstruction eg. stones, malignancy, prostate
Vesico-ureteric reflux
Neuropathic bladder (diabetics)
Foreign bodies
How does age predispose to UTIs?
Prostatic enlargement
Lose the bactericidal function of prostatic fluid
Weak pelvic floor muscles in women cause the uterus to press on the bladder
What are the routes an organism can take to cause a UTI?
Ascending
Haematogenous
Direct (ie. fistulas)
What is the most common UTI-causing pathogen?
E.coli
What pathogen is associated with stone formation?
Proteus
Urease promotes stone formation
Which pathogens are opportunistic?
Enterococci
Pseudomonas
Which pathogens are associated with HCAIs?
Enterobacterales
Pseudomonas
Enterococcus faecalis
What is needed to diagnose a UTI?
Clinical symptoms with supporting evidence
ie. bacturia isn’t the same as a UTI
What cases should bacturia be treated?
Pregnancy
If urinary tract has been manipulated
What specimens can be used in the investigation of a UTI?
Midstream urine
Catheter specimen urine
Nephrostomy or ileal conduit
Blood if systemically unwell
What investigations are done to confirm UTI?
Dipstick
Microscopy, culture and sensitivity of specimen
- >10 pus cells
- >10^5 colonies on chromogenic agar
What do colony sizes less than 10^5 mean?
10^4 needs clinical judgement
10^3 means sample was probably contaminated
What is the use of dipsticks in UTIs?
Useful to rule out UTIs: if negative for nitrites and leucocytes then very unlikely
What is the treatment length for
a) female cystitis
b) male cystitis
c) pyelonephritis
a) 3 days
b) 7 days
c) 7-14 days
Why is asymptomatic bacturia treated in pregnancy?
Can become pyelonephritis which can increase the risk of miscarriage and prem birth
Why is the risk of UTI increased in pregnancy?
Smaller bladder size
Hormones reduce the tone of the urethral muscle
Stasis due to pressure from uterus
What imaging is used for follow up care of UTIs in children?
Ultrasound to show structural abnormalities
DMSA scan to show renal parenchymal defects after infection
Micturating cystourethrogram to show reflux
Why is there an increased risk of UTIs in diabetics?
Neuropathy causes bladder dysfunction
Glucosuria is a good medium for bacteria
What is the treatment of acute pyelonephritis?
Cefuroxime and gentamicin
What is sterile pyuria?
WBCs in urine but nothing on culture
What are the causes of sterile pyuria
Antibiotics
Tumours, stones
Chlamydia and other STIs
TB and brucellosis
Which pathogen most commonly spreads haematogenously to the kidneys?
TB
