Lecture 17 - urinary tract infection Flashcards
Urinary defences against infection
Micturition - removes pathogens Vesico- uretal valves - prevents back flow of urine Mucosal barrier Acidic urine Immunulogical defense
Cystitis
Infection in the bladder
Pyelonephritis
Infection in the kidney
Requires longer treatment and further investigation
Prevalence of UTI
Infancy - incompetent valve Children - poor hygiene Women - shorter urethras Adolescents - engage in sexual activity elderly - weaker immune system and enlarged prostate
Causes of UTIs
Obstruction - stones, enlarged prostate
Impaired emptying of bladder- - multiple sclerosis, stroke
Pregnancy - enlarged uterus compresses bladder
Abnormal renal tract - vesico-uteric reflux in children
Impaired host defense - diabetes mellitus and immunosuppression
What bacteria causes UTIs most commonly
E coli - gram negative coliforms
Virulence factors of E coli
Flagellar - movement
Pili - attachment to mucus membrane
Lipid polysaccharide membrane - resist host defences
Haemolysin toxins - damages host membranes and causes renal damage
Presentation of cystitis
Dysuria Nocturia Pyrexia Cloudy urine Urgency Haematuria Suprapubic tenderness
Presentation of pyelonephritis
High fever Rigor Loin pain and tenderness Nausea and vomiting \+/- symptoms of cystitis
Uncomplicated UTI
Infection by a usual organism in a patient with normal urinary function and tract
Complicated UTI
More than 1 factor that predisposes them to persistent, recurrent infection or treatment failure e.g.
- Abnormal urinary tract
- Virulent organism - staph aureus
- Impaired host defence - poorly controlled DM
- Impaired renal function
Requires urine culture
Practised complicated cases
Children
Pregnant women
Some men
Specimen collection methods
Mid stream urine Clean catch - children Collection bag Catheter sample Suprapubic aspiration - invasive so not done
Culture urine within 4 hours of collection or preserve in refrigerator or boric acid
Urine dipstick tests
Leukocyte esterase - WBCs Nitrates - coliforms pH Protein Blood
When to do a urine diptick
If 1 or less symptom of:
- dysuria
- Nocturia
- cloudy urine
Microscopy of urine
WBC
RBC
Epithelial cells
Bacteria
Why use urine culture
Investigation of complicated infections
Epidemiology isolates - create guidlines
Antibiotic susceptibility data
Imaging
Consider in all children with UTI
Septic patients for renal involvement
Males - posterior urethral valves
Female - vesicoureteric reflux
Sterile pyuria
Raised WBCs in urine due to:
- Prior antibiotics
- Appendicitis
- Vaginal infection or inflammation
- Urethritis
Tuberculosis
Asymptomatic bacteriuria
Only treated in pregnant women as untreated leads to high risk of premature labour and pyelonephritis
Treatment of UTIs
Increased fluid intake
Analgesia
Cranberry products
Treated underlying cause
Uncomplicated - 3 day course of antibiotics:
Complicated - 5 -7 day course of antibiotics
Treatment of cystitis
Uncomplicated: 3 days Complicated - 5 -7 day - trimethoprim - nitrofurantoin - pivmecillinam
Prophylaxis
Can be given if more than 3 episodes in 1 year without any treatable underlying condition
