Urinary Tract Infections Flashcards
UTI definition
the inflammatory response of the urothelium to bacterial invasion
UTIs are the result of
- reduced host defences
- micro-organism pathogenicity
usually a combination of these factors leads to the development of symptomatic infection
Less common micro-organsims can result in UTI by two types of spread:
- haematonegenous spread
- direct transmission from adjacent infected
organs
Less common micro-organsims can result in UTI by two types of spread:
- haematonegenous spread
- direct transmission from adjacent infected
organs
UTIs can be broadly divided into (2):
- uncomplicated: occuring in a patient with a
structurally and functionally normal urinary
tract - complicated
Bateriuria definition
presence of bacteria in the urine
Pyuria
presence of white cells in the urine
Sterile pyuria
presence of white cells in the urine with bacteriuria
Asymptomatic bacteriuria definition
presence of bacteria on two consecutive urine cultures without symptoms of upper or lower UTI
What is required for a UTI to be classed as a complicated UTI (2):
- positive urine culture with a risk factor
Recurrent UTI (4):
- episode of UTI after documented
successful resolution of an earlier episode - frequency of at least twice in the previous
6 months - three times in the last 12 months
- classed as persistent or re-infection
Persistent UTI:
- recurrent UTI caused by the same
organism - indicates focus of infection in the urinary
tract - stones/fistula
Re-infection UTI:
- recurrent UTI caused by different
organisms - indicates susceptibility to UTI (genetic)
- associated with (3):
- poor hygiene
- sexual intercourse
- post-menopause
- 95% of female UTIs are due to re-infection
Classification of UTI table
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What % of females have one UTI in their lifetime?
50%
What % of UTIs occur in men?
20%
What % of elderly have asymptomatic bacteriuria?
20%
Why are women more susceptible than men to UTIs?
- female urethra is shorter and straighter
- facilitates bacterial access to the bladder
In postmenopausal women, what may predispose patients to UTIs?
- oestregne deficiency
- from increased colonisation with E.coli
In men, UTI is often associated with
urinary obstruction eg bladder outlet obstruction due to prostate enlargement
Use of what type of catheters can cause UTIs
- indwelling catheters (men and women)
Male urethra
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3 risk factors of uncomplicated UTIs:
- female gender
- older
- younger
Risk factors of complicated UTIs?
- indwelling catheters
-immunosuppression - urinary tract abnormalities
- antibiotic exposure
Aetiology of UTI:
- UPEC
- K. pneumoniae
- S. saprophycticus
- Candida
- S. aureus
UTIs: Anatomical Sites (6):
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Classification of UTIs
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Risk factors for complicated UTIs:
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Acute Cystitis
- the infection and inflammation of
the bladder urothelium - often associated with lower urinary
tract symptoms: dysuria, frequency,
urgency, suprapubic pain, offensive
urine - if dysuria and frequency are both
present then probability of UTI >90
and EMPIRICAL antibiotic treatment
indicated
Acute Pyelonephritis
- infection/inflamm of kidney
- symptoms: flank pain, nausea,
vomiting and pyrexia - must differentiate early between
acute, uncomplicated and
obstructive (stone from kidney to
ureter, backpressure causes this,
antibiotics won’t help) - can result in urosepsis
- imaging of upper urinary tract key
for evaluating obstruction or renal
stones
Catheter associated UTI:
- catheters provide a focus for
bacterial biofilm formation - long0term indwelling catheters
often colonised with two or more
organisms
When is antibiotic treatment indicated in patients with catheter associated UTI?
- only if symptomatic
Epididymo-orchitis
- inflammation of the epididymis and
or testicle - causes pain, swelling and often
unilateral - antimicrobials selected empirically
that in young, sexually active men
c. trachomatis is usually causative - in older men with BPH or other
micturition disturbances, generally
gram neg e-coli
Pathogenesis of UTIs:
- faecal flora (gram neg) colonise
perineum, UTI usually results from
retrograde ascent of these
microorganisms - bacteria adhere to the urothelium
and release toxins
UTI: UPEC: Pathogenesis:
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Clinical Presentation of UTI: Mneumonic:
FUND
Clinical Presentation of UTI: FUND:
- frequency
- urgency
- nocturia
- dysuria
- foul odour
- suprapubic pain/tenderness
indicative of cystitis - costovertebral angle
pain/tenderness indicative of
pyelonephritis - Fever
- hypotension and altered mental
state may indicate sepsis
Clinical Presentation of Pyelonephritis:
- fevers, rigors, loin pain
- renal angle tenderness
- costovertebral angle pain
- if pain radiates to groin = stone
- risk of bacteraemia
UTI Investigations:
- urine dipstick
- microscopy
- urine culture
- renal imaging
UTI Investigations: Urine Dipstick:
- urinary pH: alkaline may indicate a
urea-splitting organism - leukocyte esterase: inflammatory
cells - nitrite: enterobacteria family
- blood: cystitis may cause but
malignancy should be ruled
out - protein: glomerulopathy, large WBC
count may lead to a false
positive
If a urine dipstick shows presence of nitrites but not leukocytes then
does not necessarily suggest a UTI
UTI Investigations: Microscopy:
- midstream sample
- centriguged
- more 5 leukocytes per high power
field denotes pyruria - sterile pyuria may occur with:
- bacterial infections (renal
abscesses)
- partially treated UTI
UTI Investigations: Urine Culture:
- gold standard investigations
- 0.1 ml urine delivered onto each half
of split agar plate - number of colonies estimated after
overnight incubation - more than 10to the power 5 colony
count for diagnosing UTI - 50% symptomatic women have a
lower colony count - 100 colonies may signal infection in
symptomatic patients
Urinary bacteria generally gram positive or negative?
Gram negative
Gram staining:
Pink signifies
Purple signifies
pink = gram neg
purple = gram pos
Is E.coli gram positive or negative?
Negative
Gram positive organisms include:
- enterococcus faecalis
- staphylococcus
UTI Investigations: Renal Imaging:
- ultrasound
- CT
- in pts who are systemically ill, with a
history of kidney stones - to rule out an infection behind an
obstruction that mimics an abscess
Uncomplicated cystitis: Management: Women:
- empiric treatment in healthy, non-
pregnant women with classic
symptoms of acute UTI without
evidence of pyelonephritis - urinary dipstick is only test required
- if abnormal then pelvic exam and
urine culture could be indicated
Uncomplicated Cystitis: Management: Men:
- urine dipstick and culture generally
performed before therapy
Uncomplicated Pyelonephritis: Management:
- urinary dipstick is usually positive
- urine culture sent for definitive
diagnosis, to find causative
organism
Complicated UTI: Management:
- suspected in pts who relapse and
don’t improve with therapy - results when anatomic or functional
abnormality of urinary tract or a
resistant infection - cather associated UTI always
complicated - urine culture recommended
Asymptomatic Bacteriuria: Management:
- screening for asymptomatic
bacteruria unnecessary - pregnant women screened and
treated if bacteria count 10,000 or
more to decrease risk of
pyelonephritis - patients undergoing renal or
urologic procedures also benefit
from screening
UTI: Antibiotic Treatment:
- empiric: consider target organisms,
route of administration, side effects,
resistance - uncomplicated UTI usually need 5
days antibiotics (broad-spectrum)
whilst waiting for culture
UTI Treatment: Antibiotics: Empiric Drugs:
- nitrofurantoin (4x day)
- trimethoprim (x2 day)
- 5-7 days for trimethoprim
Prevention of recurrent UTIs:
- correct underlying host cause
(diabetes mellitus) - antibiotic prophylaxis (temporary)
- behavioural changes:
- high fluid intake
- void after intercourse
- double voiding (before and
after)
- OTC: cranberry juice - oestregen replacement for post
menopausal women
Prevention of Catheter Acquired UTIs:
- only use for a good reason
- asceptic insertion
- closed drainage system
- remove promptly when no longer
indicated
