Urinary tract infection

Question 1

What is urinary tract infection?

Answer 1

A UTI is an infection of the kidneys, bladder, or urethra. Infectious cystitis is the most common type of UTI, which is caused by a bacterial infection of the bladder.
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The presence of a pure growth of >105 organisms per mL of fresh MSU (not diagnostic - 1/3 women with symptoms of UTI will have negative MSU) 

MSU= midstream specimen of urine

Question 2

How can a UTI be classified?

Answer 2

1. Lower UTI- affecting the urethra (urethritis), bladder (cystitis) or prostate (in MEN - prostatitis) 
2. Upper UTI- affecting the renal pelvis (pyelonephritis) 
3. Uncomplicated UTI- normal renal tract and function 
4. Complicated UTI 
   - abnormal/reduced renal/genitourinary tract function, 
   - voiding difficulty/obstruction, 
   - impaired host defences, virulent organism (e.g.S. aureus) 

Question 3

What causes a UTI?

Answer 3

MOST UTIs are caused by Escherichia coli 
Other causative organisms: 
- Staphylococcus saprophyticus 
- Proteus mirabilis 
- Enterococci 
Atypical organisms that can cause UTI (usually in immunocompromised individuals): 
- Klebsiella - hospital acquired 
- Candida albicans 
- Pseudomonas aeruginosa 

Question 4

What are the risk factors for a UTI?

Answer 4

o FEMALE
o Sexual intercourse
o Exposure to spermicide
o Pregnancy – in pregnant, usually asymptomatic until serious pyelonephritis or premature delivery supervenes so must do routine dipstick
o Menopause
o Immunosuppression
o Catheterisation
o Urinary tract obstruction
o Urinary tract malformation

Question 5

Summarise the epidemiology of urinary tract infections

Answer 5

● VERY COMMON
● 1-3% of GP consultations
● The majority of women will have a UTI in their lifetime
● MUCH more common in FEMALES

Question 6

What are presenting symptoms of urinary tract infections?

Answer 6

1. Cystitis
   o Frequency
   o Urgency
   o Dysuria
   o Haematuria
   o Suprapubic pain
2. Prostatitis
   o Flu-like symptoms
   o Low backache
   o Few urinary symptoms
   o Swollen or tender prostate on
   o flank pain
3. Acute Pyelonephritis
   o High fever
   o Rigors
   o Vomiting
   o Loin pain and tenderness
   o Oliguria “low urine output” (if AKI)

Question 7

What signs of UTI can be found on physical examination?

Answer 7

● Fever
● Abdominal or loin tenderness
● Foul-smelling urine
● Distended bladder (occasionally)
● Enlarged prostate (if prostatitis)

Question 8

What investigations are used to diagnose/ monitor a UTI?

Answer 8

1. Urine Dipstick → 1st line, most important initial diagnostic test. Findings include positive leukocytes and nitrites.
2. MSU should be sent for MC&S (microscopy, culture and sensitivities) → gold standard. Identify bacteria.
   - Pyelonephritis → will have white cell casts
   - Urine Culture → determine causative pathogen & adapt antibiotic treatment. E.coli is intesely pink on MacConkey agar (positive lactose fermentation).
3. Blood Cultures → if signs of sepsis

Question 9

How are UTI’s managed?

Answer 9

1. Uncomplicated Lower UTI → Nitrofurantoin or Trimethoprim.
   2nd line is beta-lactam antibiotics (Amoxicillin) or cefalexin
   - Women have 3 day prescription (7 if pregnant). Men have 7 day prescription.
   *Asymptomatic bacteriuria in pregnant women = still treat with nitrofurantoin (avoid near term) or amoxicllin to avoid risk of progression to pyelonephritis.
   - Trimethoprim ⇒ folate antagonist hence should be avoided in first trimester of pregnancy.
   - and the British National Formulary (BNF) recommends avoiding it for the duration of pregnancy.
   - Trimethoprim causes competitive inhibition of creatinine secretion from the renal tubules. It leads to markedly increased creatinine without any true decrease in glomerular filtration rate.
   - Nitrofurantoin ⇒ should be avoided near end of pregnancy.
   - Nitrofurantoin is contraindicated in patients with an eGFR of less than 45 & pts with G6PD deficiency (can cause haemolysis)
2. Don’t treat asymptomatic bacteriuria in catheterised patients (if symptomatic, 7 day abx course and change catheter).
3. Acute Pyelonephritis → hospital admission + broad-spectrum cephalosporin or a quinolone (for 10-14 days) can develop into a very serious condition and immediate intervention is warranted. In the presence of infection, a ureteric stent or nephrostomy should be inserted as a matter of priority, before dealing with the underlying cause.
4. Prevention → increased fluid intake, timely bladder voiding, postcoital voiding (peeing within 15 minutes of sexual intercourse), clean intermittent catheterization, chemoprophylaxis (the administration of a medication for the purpose of preventing disease or infection)