MI: Urinary Tract Infection

Question 1

In which situation is asymptomatic bacteriuria clinically significant?

Answer 1

Pregnancy - associated with increased risk of complications

Question 2

What is the difference between uncomplicated and complicated UTI?

Answer 2

• 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)

Question 3

In which groups of patients are UTIs considered ‘complicated’?

Answer 3

• Men
• Pregnant women
• Children
• Hospitalised patients

Question 4

Which organism most commonly causes UTI?

Answer 4

E. coli

Question 5

List some other organisms that cause UTI.

Answer 5

• Proteus mirabilis
• Klebsiella aerogenes
• Enterococcus faecalis
• Staphylococcus saprophyticus
• Staphylococcus epidermidis (can cause infection in the presence of prosthesis (e.g. procedures, indwelling catheters))

Question 6

Which virulence factor allows S. saprophyticus to stick to the urinary tract epithelium?

Answer 6

P-fimbriae

NOTE: S. saprophyticus causes infection in young women

Question 7

List some antibacterial host defences in the urinary tract.

Answer 7

• Urine (osmolality, pH, organic acids)
• Urine flow and micturition
• Urinary tract mucosa (bactericidal activity, cytokines)

Question 8

What is an ascending UTI?

Answer 8

The infection ascends from the female introitus and periurethral area

Question 9

List some causes of urinary tract obstruction.

Answer 9

Extra-renal

• Valves, stenosis or bands
• Calculi
• BPH

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

Question 10

What is vesicoureteric reflux?

Answer 10

• 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

Question 11

Describe how UTI can become established via the haematogenous route.

Answer 11

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

Question 12

Outline the symptoms of UTI in:

1. Neonates and childrne < 2 years
2. Children > 2 years

Answer 12

Neonates and children < 2 years:

• Failure to thrive
• Vomiting
• Fever

Children > 2 years:

• Frequency
• Dysuria
• Abdominal pain

Question 13

List some symptoms of upper UTI.

Answer 13

• Fever (and rigors)
• Flank pain
• Lower urinary tract symptoms

Question 14

Describe the symptoms of UTI in older patients.

Answer 14

• Mostly asymptomatic
• Atypical symptoms (e.g. confusion)

NOTE: classic symptoms such as frequency and dysuria are common in older people and does not necessarily suggest that there is an infection

Question 15

List some investigations for uncomplicated UTI.

Answer 15

• Urine dipstick
• MSU for urine MC&S
• Bloods - FBC, CRP, U&E

Question 16

List some further investigations that may be considered in complicated UTIs.

Answer 16

• Renal ultrasound scan
• IV urography

Question 17

What are nitrites in the urine specific for?

Answer 17

They are produced by E. coli

Question 18

What does nitrite-negative leukocyte-positive urine suggest?

Answer 18

UTI caused by non-coliform bacteria

Question 19

List some patient groups in whom culture and sensitivities should be performed.

Answer 19

• Pregnancy
• Children
• Pyelonephritis
• Men
• Catheteristed
• Failed antibiotic treatment
• Abnormalities of the genitourinary tract
• Renal impairment

Question 20

What does the presence of white cell in the urine (pyuria) suggest?

Answer 20

Infection

Question 21

What does the presence of sqaumous epithelial cells in the urine suggest?

Answer 21

Contamination

Question 22

What is the microbiological definition of UTI?

Answer 22

Culture of single organisms > 10⁵ 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)

Question 23

What number of white cells in the urine represents inflammation?

Answer 23

More than 10⁴/mL

Question 24

In which patient groups should screening of the urine for white cells for MC&S NOT be performed?

Answer 24

Immunocompromised patients, pregnant women and children

Question 25

List some causes of sterile pyuria (white cells in urine but no culture growth).

Answer 25

* STIs (e,g, chlamydia) * TB * Prior antibiotic treament (MOST COMMON) * Calculi * Catheterisation * Bladder cancer

Question 26

What type of agar is used for urine culture? What do the colours suggest?

Answer 26

Chromogenic agar * Pink = *E. coli* * Blue = other coliforms * Light blue = Gram-positives

Question 27

List some methods of sampling urine for investigations.

Answer 27

* MSU * Catheterisation * Suprapubic aspiration (usually in young children)

Question 28

What type of therapy may be needed for patients with UTIs caused by ESBL producing organisms?

Answer 28

Outpatient parenteral antibiotic therapy (OPAT)

Question 29

Outline the treatment options for: 1. Uncomplicated UTI in women 2. UTI in pregnant or breastfeeding women 3. UTI in men 4. Pyelonephritis or systemically unwell with a UTI 5. Catheter-associated UTI

Answer 29

1. **Uncomplicated UTI in women** * Cefalexin 500 mg BD PO for 3 days OR * Nitrofurantoin 50 mg POQ QDS for 7 days (check renal function) 2. **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 3. **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 4. **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 5. **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

Question 30

In which groups of patients is a short course of antibiotics not appropriate?

Answer 30

* Women with a history of UTI caused by antibiotic resistant organisms * More than 7 days of symptoms * Men

Question 31

In which patients do *Candida* UTIs tend to occur?

Answer 31

Patients with indwelling catheters

Question 32

How should *Candida* infections due to catheters be treated?

Answer 32

Remove the catheter NOTE: there is no evidence of oral fluconazole being better than no intervention

Question 33

In which exceptional cases should *Candida* UTI be actively treated?

Answer 33

* Renal transplant patients * Patients waiting to undergo elective urinary tract surgery

Question 34

Which part of the kidney is more susceptible to infection?

Answer 34

Renal medulla

Question 35

What is the main treatment option for pylenephritis?

Answer 35

Co-amoxiclav with or without gentamicin

Question 36

List some complications of pyelonephritis.

Answer 36

* Perinephric abscess * Chronic pyelonephritis (scarring, renal impairment) * Septic shock * Acute papillary necrosis