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)