Urinary Tract Infection
Very common
Significant cause of morbidity and mortality.
Occurs anywhere between the glomerulus
and the external os of the urethra
– Upper UTI is above the bladder
– Lower UTI is from the bladder down
Urinary Tract Infection
Stages of life :
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Infancy
Preschool
Honeymoon cystitis
Pregnancy
Prostatism
UTI - Who is susceptible?
Mostly females due to the (20cm) shorter urethra
(30:1).
Exceptions are neonatal boys who are 4X more
likely than neonatal girls to have an UTI –
reasons not clear.
Elderly men become more susceptible due to
prostatic hyperplasia but never overtake the
females (2:1).
The one equalising factor is the urethral
catheter.
UTI
• Urinary tract and bladder are normally
sterile apart from the anterior urethra
which may be colonised with skin flora
• Presence of microflora alone does not
establish significance
• Pyuria may or may not, reflect a response
to infection
Urinary Tract Infection
Sterile Pyuria:
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Renal TB
Glomerulonephritis
Urethritis
Pelvic Abscess
Schistosomiasis
Viral cystitis
Prostatitis
GU Fistula
Stones
UTI - Frequency and dysuria
syndrome
• Bacterial Cystitis
Characterised by significant bacteriuria,
pyuria and sometimes haematuria.
• Abacterial cystitis. Previously known as
‘urethral syndrome’. No bacteria are
cultured from urine and the cause is
usually unknown. (Often gut and vaginal
anaerobes)
UTI
Infections are described as
‘uncomplicated’ as in most OPD or GP
patients.
Or ‘complicated’ eg. in patients with
congenital or surgical abnormalities of the
tract or those having urological procedures
and / or the presence of a urethral
catheter.
UTI – Urinary Catheter
Hospital-Acquired UTI
1. Urinary catheter for relief of retention
2. Intermittent catheterisation following head or
spinal cord injury, may be required several
times a day.
3. Indwelling catheters - continuous drainage
may be needed following spinal cord lesion or
shorter term post TUR.
4. Any instrumentation or surgery on the urinary
tract increases the chances of HA-UTI.
Hospital-Acquired UTI
Care and insertion of Urethral Catheter :
• Motives?
• Choice of catheter (smallest bore and balloon)
• Insertion
• Sterile procedure but NO disinfectant.
• Bag emptying - maintain closed system.
• Catheter toilet
• Urine collection
• Limit washouts and antibiotics.
UTI
Almost all UTI’s are caused by organisms
ascending the tract.
Few are caused by haematogenous
transport of bacteria and other agents especially M. tuberculosis and Salmonella
spp. Also rarely Schisto. haematobium,
Histoplasma and viruses such as CMV
and Adenovirus
Recognised Urinary Pathogens
Mostly Gram-negative bacilli
Enterobacteriaceae
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•
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E. coli
Proteus spp
Klebsiella spp
Enterobacter spp
• Citrobacter spp
• Serratia spp
• Providencia spp
Recognised Urinary Pathogens
Other Gram negatives :
Pseudomonadaceae
• Pseudomonas spp
• Alcaligenes spp
Gram-negative coccobacilli
Acinetobacter spp
Recognised Urinary Pathogens
Gram-positive cocci :
Micrococcaceae :
• Staph saprophyticus
• Staph aureus
• Staph. epidermidis
Streptococcaceae :
• Strep faecalis and other enterococci
• Strep. agalactiae (Lancefield group B)
Also yeasts (Candida species)
UTI – Asymptomatic Bacteriuria
A significant bacteriuria (>100,000/ml) without
symptoms - not treated except for at risk patients:
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Pregnancy (To prevent acute Pyelonephritis)
Renal Disease diabetes or polycystic kidneys
The immunocompromised
Anatomical or neurological defects
Patients about to undergo urological examination
Children – require investigation for congenital reflux
abnormalities
UTI – Acute Pyelonephritis
Predisposing factors :
• Prostatic enlargement
• Pregnancy (3rd Trimester)
• Children with congenital malformations
• Obstruction, calculi, tumours
• Urethral catheterisation.
Diagnosis as for UTI
UTI – Lab. Diagnosis
Specimens are frequently contaminated with
normal flora from perineum or genitalia.
Contamination reduced by taking
‘midstream urine’ specimens (MSU)
having cleaned the genitalia
UTI – Lab. Diagnosis
Collection methods :
• MSU/CSU
• Adhesive bags
• Suprapubic stimulation (Babies)
• Suprapubic aspiration
NEVER by catheterisation
UTI – Lab. Diagnosis
Must be transported rapidly to lab and
refrigerated if delayed.
Use of transport kits have been
recommended but often inhibitory to
organisms
UTI – Lab. Diagnosis
Interpretation of results for MSU:
1. >100,000 bacteria/ml urine – UTI
2. 10,000 bacteria/ml urine - usually either
contamination or prior antibiotics
3. 1,000 bacteria/ml urine – Usually
contamination but may be significant with
acute dysuria and frequency
4. More than one organism or mixed growth:
Contamination likely
UTI Factors affecting bacterial
counts
• Stage of infection
• Fluid intake/ frequency of micturition.
• Presence of antibiotics and other
antibacterial substances (eg. Urea)
• Underlying illness of the patient.
• Whether patient is post-operative
• The presence of a urinary catheter
• Residual urine
UTI Factors affecting bacterial
counts cont’d
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Probably the age and sex of the patient
pH of urine
The growth rates of the organisms
The number of bacteria in a colony
forming unit
• The site of infection
UTI – Lab. Diagnosis
White cell count in urine is normally less than 10
white cells / cubic mm of urine.
Figures above this suggest an infection.
Though the WCC may be raised for other reasons
eg :
Interstitial neuropathies (diabetes and analgesics)
• Acute glomerulonephritis
• Renal failure
• Neoplasms
UTI – Lab. Diagnosis
Reasons for raised WCC cont’d:
• Postoperative
• Catheterisation
• Fevers in children
• Spread of inflammation of neighbouring
sites (eg appendix or bowel)
• White cells from preputial sac or vagina
may contaminate the urine
UTI - Factors predisposing bladder
to bacteruria
Factors which facilitate ascent of organisms
up the urethra :
• Urethral, bladder or prostatic surgery
• Sexual intercourse
• Vaginal prolapse
UTI - Factors predisposing bladder
to bacteruria
Factors which result in the stagnation of urine in
the bladder :
• Infrequent micturition
• Inadequate fluid intake (or urinary output)
• Obstruction (Urethral valves, strictures, prostatic
hypertrophy, constipation, calculi and catheters)
• Vesico-ureteric reflux
• Impairment of neurogical control of bladder
• Bladder diverticula
UTI Treatment
1.
2.
3.
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Increase fluid intake (= urine output)
Acidify urine
Antibiotics
Uncomplicated –
3 days
Pyelonephritis –
7 -14 days IV
Asymptomatic bacteriuria in pregnancy –
3-7 days