MI: Urinary Tract Infection Flashcards
In which situation is asymptomatic bacteriuria clinically significant?
Pregnancy - associated with increased risk of complications
What is the difference between uncomplicated and complicated UTI?
- Uncomplicated - infection in a structurally and neurologically normal urinary tract
- Complicated - infection in a urinary tract with functional or structural abnormalities (includes indwelling catheters and calculi)
In which groups of patients are UTIs considered ‘complicated’?
- Men
- Pregnant women
- Children (may have structural abnormality)
- Hospitalised patients
Which organism most commonly causes UTI?
E. coli
List some other organisms that cause UTI.
- Proteus mirabilis - struvite kidney stones
- Klebsiella aerogenes
- Enterococcus faecalis
- Staphylococcus saprophyticus - UTI young healthy women - probably 2nd after E. coli
- Staphylococcus epidermidis - can cause infection in the presence of prosthesis (e.g. procedures, indwelling catheters)
Which virulence factor allows E. coli to stick to the urinary tract epithelium?
P fimbriae
List some antibacterial host defences in the urinary tract.
- Urine (osmolality, pH, organic acids)
- Urine flow and micturition
- Urinary tract mucosa (bactericidal activity, cytokines)
What is an ascending UTI?
Infection of the lower urinary tract may pass up the ureters into the renal pelvis and parenchyma
List some causes of urinary tract obstruction.
Extra-renal
- Valves, stenosis or bands
- Calculi
- BPH
- External ureter compression (gravid uterus, tumour)
Intra-renal
- Nephrocalcinosis
- Nephropathy (uric acid, analgesic, hypokalaemic)
- Polycystic kidney disease
Neurogenic malfunction
- Poliomyelitis
- Tabes dorsalis (demyelinating condition caused by advanced syphilis)
- Diabetic neuropathy
- Spinal cord injuries
What is vesicoureteric reflux?
- A condition in which urine can reflux into the ureters
- It results in a residual pool of infected urine in the bladder after voiding
- It can result in scarring of the kidneys
Describe how UTI can become established via the haematogenous route.
The kidney is a frequent site for abscesses in patients with S. aureus bacteraemia or endocarditis (not really a UTI)
NOTE: Gram negative bacilli like E. coli rarely spreads via the haematogenous route
Outline the symptoms of UTI in:
- Neonates and childrne < 2 years
- Children > 2 years
Neonates and children < 2 years: (non-specific)
- Failure to thrive
- Vomiting
- Fever
Children > 2 years: (more localised)
- Frequency
- Dysuria
- Abdominal or flank pain
List some symptoms of lower UTI
- Bladder and urethral mucosal irriation - frequent and painful urination
- Suprapubic pain
- Haematuria
- Absence of fever (most of the time)
List some symptoms of upper UTI.
- Fever (and rigors)
- Flank pain
- Lower urinary tract symptoms (frequency, urgency, dysuria)
- At times LUTS preceed the onset of fever and upper tract symptoms
Describe the symptoms of UTI in older patients.
- Mostly asymptomatic
- Atypical symptoms (e.g. confusion, abdominal pain)
NOTE: classic symptoms such as frequency and dysuria are common in older people and does not necessarily suggest that there is an infection
Would you do a urine dip in suspected UTI in >65 year old and why?
No - dipsticks become unreliable in ages >65 due to the increased likelihood of asymptomatic bacturia (which is not harmful)
List some investigations for uncomplicated UTI.
- Urine dipstick
- MSU for urine MC&S
- Bloods - FBC, CRP, U&E
List some further investigations that may be considered in complicated UTIs.
- Renal ultrasound scan
- IV urography
What are nitrites in the urine specific for?
They are produced by E. coli
What does nitrite-negative leukocyte-positive urine suggest?
UTI caused by non-coliform bacteria
List some patient groups in whom culture and sensitivities should be performed.
- Pregnancy
- Children
- Pyelonephritis
- Men
- Catheteristed
- Failed antibiotic treatment
- Abnormalities of the genitourinary tract
- Renal impairment
What does the presence of white cell in the urine (pyuria) suggest?
Infection
What does the presence of sqaumous epithelial cells in the urine suggest?
Contamination
What is the microbiological definition of UTI?
Culture of single organisms >10^5 colony forming units/mL with urinary symptoms
NOTE: this threshold may be reduced for organisms that are known to cause UTI (e.g. E. coli and S. saprophyticus)
What number of white cells in the urine represents inflammation of the urinary tract?
More than 10^4/mL
In which patient groups should screening of the urine for white cells for MC&S NOT be performed?
Immunocompromised patients, pregnant women and children
List some causes of sterile pyuria (white cells in urine but no culture growth).
- Prior antibiotic treament (MOST COMMON)
- STIs (e.g. chlamydia)
- TB
- Calculi
- Catheterisation
- Bladder cancer
What type of agar is used for urine culture? What do the colours suggest?
Chromogenic agar
- Pink = E. coli
- Blue = other coliforms
- Light blue = Gram-positives
List some methods of sampling urine for investigations.
- MSU
- Catheterisation
- Suprapubic aspiration (usually in young children)
What type of therapy may be needed for patients with UTIs caused by ESBL producing organisms?
Outpatient parenteral antibiotic therapy (OPAT)
Outline the treatment options for:
- Uncomplicated UTI in women
- UTI in pregnant or breastfeeding women
- UTI in men
- Pyelonephritis or systemically unwell with a UTI
- Catheter-associated UTI
-
Uncomplicated UTI in women
- Cefalexin 500 mg BD PO for 3 days OR
- Nitrofurantoin 50 mg POQ QDS for 3 days (check renal function)
-
UTI in pregnant or breastfeeding women
- Cefalexin 500 mg BD PO for 7 days
- 2nd line: co-amoxiclav 625 mg TDS PO for 7 days
-
UTI in men
- Cefalexin 500 mg BD PO for 7 days OR
- Ciprofloxacin 500 mg BD PO for 14 days if suspicion of prostatitis
- Chronic prostatitis: ciprofloxacin 500 mg BD PO for 4-6 weeks
-
Pyelonephritis or systemically unwell with a UTI
- Co-amoxiclav 1.2 g IV TDS
- Consider adding IV amikacin or gentamicin
- Penicillin allergy: ciprofloxacin 400 mg IV BD
-
Catheter-associated UTI
- Remove catheter (but give stat doses before removal of infected catheter)
- Gentamicin 80 mg STAT IV/IM 30-60 mins before procedure
OR - Amikacin 140 mg STAT IV/IM 30-60 mins before procedure
In which groups of patients is a short course (3-days) of antibiotics not appropriate?
- Women with a history of UTI caused by antibiotic resistant organisms
- More than 7 days of symptoms
- Men
i.e. any complex UTI - short course only appropriate for women with uncomplicated UTI
In which patients do Candida UTIs tend to occur?
Patients with indwelling catheters
How should Candida infections due to catheters be treated?
Remove the catheter
There is no evidence of oral fluconazole being better than no intervention
In which exceptional cases should Candida UTI be actively treated?
- Renal transplant patients
- Patients waiting to undergo elective urinary tract surgery
Which part of the kidney is more susceptible to infection?
Renal medulla
What is the main treatment option for pylenephritis?
IV co-amoxiclav with or without gentamicin
Why might imaging be included in the diagnostic workup for pyelonephritis?
To see whether there are any structural abnormalities or calculi
List some complications of pyelonephritis.
- Perinephric abscess
- Chronic pyelonephritis - leads to scarring and chronic renal impairment
- Septic shock
- Acute papillary necrosis
