UROLOGY - UTI Flashcards
What are common organisms causing UTI?
E.coli 70%
Klebsiella pneumoniae
Proteus mirabilis
Enterococcus faecalis
Staphylococcus saprophyticus.
What are the possible mechanisms for UTI?
Mostly caused by bacteria from a patient’s own bowel flora and ascends up the urethra
Rarely the infection may arise from bloodstream, lymphatics or by direct extension e.g. vesicocolic fistula
What virulence factors does E.coli have which makes it a common pathogen for UTI?
Fimbriae - attach organism to perineurm and urothelium
Flagella
Aerobactin (to acquire iron)
Haemolysin (to form pores)
K capsule - allows bacteria to avoid phagocytosis and inactivation by the complement
What are the innate host defences to prevent UTI?
Neutrophils
Urine osmolality and low or high pH
Complement activation with mucosal IgA
Commensalism organisms
Urine flow
Uroepithelium having tamm-horsfall proteins which have antibacterial properties
What are risk factors for UTI?
Increased bacterial inoculation - sexual activity, urinary incontinence, faecal incontinence, constipation
Increased binding of uropathogenic bacteria - spermicide use, decreased oestrogen e.g. menopause
Decreased urine flow - dehydration or obstruction
Increased bacterial growth - DM, immunosuppression, obstruction, stones, catheter, urinary tract malformation, pregnancy
What are the most typical clinical features of a lower uti?
Frequency of micturition day and night
Dysuria
Suprapubic pain and tenderness
Haematuria
Smelly urine
Fever
Distended bladder or enlarged prostate
Confusion, fatigue, incontinence in elderly
Febrile, sick, fussy with FTT in children
How are UTIs diagnosed?
Examination - vital signs, palpate for flank or suprapubic tenderness and for pelvic/abdominal masses, check for blockage if urinary catheter in situ
Urine dipstick if under 65 and not pregnant - nitrites, leukocytes, RBC
Urine culture
FBC, U&Es, CRP and blood culture if systemically unwell
Imaging e.g. USS, cystoscopy or renal ultrasound in children to check kidney malformation
What is a relapse of UTI?
Recurrence of bacteriuria with the same organism within 7 days of completion of antibacterial treatment
What is re-infection of UTI?
When bacteriuria is absent after treatment for at least 14 days followed by a recurrence of infection with same/different organism.
This is not failure to eradicate but re-invasion of a susceptible tract
What’s the natural history of outcome for UTI?
In patients with normal urinary tract, outcomes are very good
In those with abnormal urinary tracts, recurrence is more common and outcomes are less good
Recurrent UTI can cause renal scarring
Dissemination of infection can cause septicaemia (urosepsis)
Can ascend to cause pyelonephritis
Whats the difference between complicated and uncomplicated UTI?
Uncomplicated is normal renal tract structure and function
Complicated involves a structural or functional abnormality of the genitourinary tract e.g. stones, catheters, obstruction
What are symptoms of pyelonephritis?
Fever, rigor, vomiting, loin pain, cystitis symptoms, septic shock
What is reflux nephropathy?
Chronic pyelonephritis
A combination of vesicoureteric reflex and infections acquired in early childhood
An incompetent vesicoureteric valve so urine reflux up ureter and incomplete bladder emptying
Predisposes to infection and causes kidney damage (papillary damage, tubulointerstitial nephritis and cortical scarring)
Reflux ceases around puberty with growth of bladder base
What does chronic reflux nephropathy predispose you to in later life?
Hypertension
ESKD
How do you manage a single, isolated attack of UTI?
Antibiotics - trimethoprim-sulfamethoxazole or nitrofurantoin 5-7 days
High fluid intake >2L daily
How should you treat a UTI in men if symptoms suggest prostatitis?
A longer course of 4 weeks of fluoroquinolone
Whats the moa of nitrofurantoin?
converted by bacterial nitroreductases to electrophilic intermediates which inhibit the citric acid cycle as well as synthesis of DNA, RNA, and protein
Whats the moa of trimethoprim-sulfamethoxazole?
Sulfamethoxazole inhibits the synthesis of dihydrofolic acid. Trimethoprim inhibits thymidine and DNA synthesis. These two agents act synergistically in inhibiting folic acid synthesis.
How do antibiotic choices for UTI change in pregnancy?
Can’t give trimethoprim/sulfamethoxazole in first trimester pregnancy as they inhibit folic acid synthesis
Can’t give nitrofurantoin in 3rd trimester of pregnancy as it may cause haemolytic anaemia of the newborn
How can you prevent UTIs?
Drink plenty of water
Wipe front to back
Wash before sex and urinate after
Don’t use irritating feminine products/bubble baths
Don’t use a diaphragm, spermicide
Cranberry juice - substance in cranberries, called proanthocyanidins, might help prevent UTI-causing bacteria from sticking to the walls of the bladder and other urinary tract linings
Voiding at 2-3 hour intervals
Voiding before bed
Avoid constipation
Infection by which organism is most common for UTI caused by prolonged bladder catheterisation?
These infections are often caused by Escherichia coli and Proteus mirabilis and candida spp
Why do urine dipsticks become unreliable over 65?
Up to half of older adults and most with a urinary catheter, urine will have bacteria present without an infection
What will 50% of women with suspected UTI but negative culture have?
Urethral syndrome - irritated urethra (urinary frequency, dysuria and suprapubic discomfort)
How do you treat pyelonephritis in non-r pregnant women and men over 16?
If oral…
Co-amoxiclav 3x day for 7 days
Or ciprofloxacin, levofloxacin
If sepsis concerned then give IV
