Urinary Tract Infection Flashcards
Define urinary tract infection.
A urinary tract infection (UTI) is an infection of the kidneys, bladder, or urethra.
- Infectious cystitis = bacterial infection of the bladder.
- Pyelonephritis= infection of the kidney
- Urethritis = inflammation of the urethra.
What are the red flags for pyelonephritis?
Costovertebral angle tenderness together with fever suggests pyelonephritis.
What is the most common organism causing uncomplicated UTI?
Escherichia coli is the most common organism in uncomplicated UTI/pyelonephritis.
How are UTIs categorised?
Uncomplicated/complicated
Acute
Recurrent
How common are UTIs?
10% of women >18yrs report at least 1 UTI every year
20-40% develop recurrent UTIs
What is the aetiology of UTI?
Uncomplicated:
- E coli - 70-95%
- Staph saprophyticus - 5-20%
Complicated:
- Citrobacter and Enterobacter genera,
- P aeruginosa, enterococci,
- Staphylococcus aureus
Entry into the urinary tract can be:
- Retrograde — bacteria ascend through the urethra into the bladder.
- Via the blood stream — more likely in people who are immunosuppressed.
- Direct — for example with insertion of a catheter into the bladder, instrumentation, or surgery.
What are P. mirabilis UTIs associated with?
Proteus mirabilis = more common in males, associated with renal tract abnormalities, particularly calculi
What are the risk factors for UTI?
Premenopausal:
- Sexual activity - strongest risk factor
- Hx of UTI in childhood
- FH
Post-menopausal:
- Atrophic vaginitis
- Cystocele
- Increased post-void urine volume
- Presence of foreign body e.g. indwelling catheter, stone, suture, surgical material
- Spermicide use - e.g. nonoxynol-9, decreases vaginal lactobacilli, which facilitates vaginal Escherichia coli colonisation (also spermicide coated condoms)
- Recurrent UTI Hx
What is the pathophysiology of UTI?
Most common route of infection is via ascending pathway - colonisation of vagina may –> ascenting UTI
Type 1 pili (e.g. in E coli) bind in greater numbers to vaginal fluid from women with vaginal colonisation.
Why do post-menopausal women get more UTI? How can this be reduced?
Alkalinisation of the fluid (as occurs post menopause) causes augmented binding of type I pili of E coli to vaginal discharge.
Acidification of vaginal pH by application of topical oestrogen reduces recurrence of UTI in post menopausal woman.
What are the symptoms of UTI?
- Dysuria
- Frequency
- Urgency
- Back/flank pain
- Costovertebral angle tenderness
- Supra-pubic pain and tenderness
What are the “four symptoms and one sign” that increase probability of UTI?
Four symptoms and one sign: including dysuria, frequency, haematuria, back pain, costovertebral angle tenderness - significantly increases the probability of UTI
What are the signs of UTI?
- Haematuria
- (Costovertebral angle tenderness)
What investigations should you do for a UTI and what would you find?
Urine dipstick - nitrite and leukocyte esterase positive (if dipstick result is negative but symptoms suggest a UTI, probability of disease is still high)
Urine microscopy - bacteria, WBC, possibly red blood cell
Urine culture and sensitivity - growth of >10⁵ CFU/mL. Most specific and sensitive test.
Other:
- Renal US/CT abdo - for kidney stones, hydronephrosis, abscess, scarring
- Cystoscopy - tumour; bladder stone; foreign body; diverticulum. Only if treatment has failed or unusual/persistent symptoms
How do you manage an uncomplicated UTI?
- Oral antibiotic (without resistence)
- Nitrofurantoin (100mg BD for 5 days)
- OR Trimethoprim (160/800mg BD for 3 days)
How do you manage a complicated UTI?
Oral antibiotics:
- Ciprofloxacin (500mg BD for 7 days)
- OR amoxicillin (500mg BD for 7 days)
If complicated and requiring admission give IV gentamicin or ceftriaxone or ampicillin for ~10-14days
How do you manage an uncomplicated recurrent UTI (>3 times per year) which is
a) related to sexual intercourse
b) unrelated to sexual intercourse
- Related to sexual intercourse:
- Post-coital abx therapy
- nitrofurantoin
- if post menopausal then ADD intra vaginal oestrogen therapy
- Post-coital abx therapy
- Unrelated to sexual intercourse:
- Low dose prophylactic abx one dose when exposed to the trigger
- nitrofurantoin OD at bedtime
- Low dose prophylactic abx one dose when exposed to the trigger
How do you prevent UTI?
- There is little evidence to support hydration and urination soon after sexual intercourse for the prevention of UTIs.
- There is conflicting evidence to support cranberry for the prevention of UTIs - contains bioactive proanthocyanidin (PAC) of the A type. But 36mg are needed for prevention of UTI.
What are the possible complications of UTI?
- Sepsis
- Renal and peri-renal abscess
- AKI
- Emphysematous pyelonephritis
- Xanthogranulomatous pyelonephritis
UTI in pregnancy can cause pre-term delivery and low birth weight.
How do you treat pyelonephritis compared to lower UTI?
Broader spectrum antibiotics e.g. cephalosporin or co-amoxiclav for 7-10days
What is the treatment for pregnant women with UTI?
Nitrofurantoin 7 days PO (2nd line: amoxicillin or cephalexin)
Send urine culture in all cases and treat even if asymptomatic
What is the treatment for UTI in men?
7 days trimethoprim/nitrofurantoin
Send urine culture in all cases
Should you treat bacteruria in catheterised patients?
Do not treat asymptomatic bacteria
If symptomatic:
7 days nitrofurantoin /trimethoprim/ amoxicillin
Change catheter.
Define recurrent UTI.
Recurrent UTI is usually defined as two or more episodes of UTI in six months or three or more episodes in one year. It is more common in women and can be due to:
- Relapse — infection due to the same strain of organism or,
- Reinfection — infection due to a different organism.
How common is catheter related bacteruria?
By a few days all people will have bacteruria
What is the prognosis with UTI once on treatment?
Resolves within 3.3 days on average
In which patients should you send a urine culture?
- Pregnant
- >65yrs old
- Non-resolving symptoms
- Recurrent UTI - 2 in 6m or 3 in 12m
- Urinary catheter in situ
- Those at risk of resistance or complicated UTI
- Atypical symptoms
- Visible or non-visible haematuria
What is the typical prescription for nitrofurantoin and trimetoprim?
- Nitrofurantoin 100mg modified-release twice a day for 3/7 days (if eGFR ≥45ml/minute) or
- Trimethoprim 200mg twice a day for 3/7 days (if low risk of resistance).
