11.2 UTI's Flashcards
What is a common complication of UTI’s?
Gram-negative septicaemia
What are the defences of the urinary tract against UTI’s?
◦ Emptying of bladder during micturition
◦ Vesico-ureteral valves (stops backflow)
◦ Immunological factors
◦ Mucosal barriers (innate immune system)
◦ Urine acidity
What is the pathophysiology of UTI’s?
Ascending colonisation of bacteria from urethra up to bladder. If vesicoureteral valve is not in tact can travel up to the kidneys
What is cystitis?
Inflammation of the bladder. Usually caused by ascending UTI
What is pyelonephritis?
Inflammation of the kidney and its pelvis, caused by bacterial infection (UTI’s)
Why is there a spike in prevalence of UTI’s in infancy?
Babies with incontinent vesicoureteral valve
What are risk factors for UTI’s?
Female
Obstructive causes (stones, enlarged prostate, retroperitoneal fibrosis)
Neurological conditions affecting bladder emptying ( multiple sclerosis and stroke)
Pregnancy (enlarged uterus, hormonal effects on relaxation of musculature )
Abnormal renal tract (Vesico-ureteric reflux in children, indwelling urinary catheter)
Impaired host defence (diabetes mellitus, immunosuppression)
Why are UTI’s more prevalent in women?
Shorter urethra. Shorter distance to bladder
External urethral orifice lies in close proximity to the vagina and/or anus
What is the most common causative agent of UTI’s?
Escherichia coli - Coliforms (gram negative rod-shade bacteria)
What are the virulence factors of escherichia coli?
Flagella - allow movement up the urinary tract
Pili - allow attachment to cells mucosal membrane
Capsular polysaccharide - colonisation
Haemolysin, toxins - damages host membrane and causes renal damage
What are clinical syndromes of UTI’s?
Cystitis (lower UTI)
Pyelonephritis (upper UTI)
Chronic pyelonephritis (scarring/fibrosis of kidneys)
Asymptomatic bacteriuria (ie. pregnancy)
Septicaemia (bacteria get into blood stream, bacteriaemia resulting in sepsis)
What is the clinical presentation of cystitis?
Dysuria Cloudy urine Nocturia or frequency Urgency Suprapubic tenderness Haematuria Pyrexia (usually mild)
What is the clinical presentation of pyelonephritis?
High fever +/- rigors
Loin pain and tenderness
Nausea/vomiting +/- Symptoms of cystitis
What are potentially differentials for dysuria?
UTI’s Sexually transmitted infections Post sexual intercourse Contact with irritants Symptoms of menopause, atrophic vaginitis or vaginal atrophy
What is uncomplicated UTI?
Defined as infection by a usual organism in a patient with a normal urinary tract and normal urinary function
What is a complicated UTI?
1 or more factors that predispose to persistent infection, recurrent infection, or treatment failure:
Abnormal urinary tract
Virulent organism (ie. Staph aureus)
Impaired host defence (immunosuppression, poorly controlled diabetes mellitus)
Impaired renal function
How are UTI’s investigated?
Uncomplicated/non-pregnant women = no need for urine culture
Complicated UTI/pregnancy/male/children/suspected pyelonephritis/treatment failure/recurrent infections = culture urine
How is a sample of urine collected?
Mid-stream urine (MSU) - cleansing not required, ideally holding labia apart in women
Clean catch in children
Collection bag (20% false positives due to contamination from perineum)
Catheter sample (fresh)
Supra-pubic aspiration (invasive)
What happens to the urine sample after collection?
Must be:
- cultured within 4 hours of collecting or
- refrigerated or
- boric acid used as a preservative
Other than a urine culture, what other investigations can be used for UTI diagnosis?
Urine dipstick. Test for leucocyte esterase, nitrates, blood, protein, pH
When are urine dipsticks useful?
Useful in females <65 years with suspected uncomplicated UTI as an aid to diagnosis. Use symptoms as primary indicator of diagnosis
Useful in ruling out infection in children >3 months old
When is a urine dipstick not useful?
◦ Patients >65 years old (asymptomatic infection
common, up to half of this population would have positive dipstick in absence of UTI)
◦ Catheterised patients
What are urine samples screened for in microscopy?
White cells
Red cells
Epithelial cells
Bacteria
How long does a urine culture take?
A day
When is imaging of the urinary tract considered?
In all children with a UTI (may have predisposing factors)
Septic patients in identify renal involvement (pyelonephritis)
Males looking for posterior urethral valves
Females and children looking for vesico-ureteric reflux
Why might patients present with sterile pyuria?
Usually due to prior antibiotics before sample taken
Urethritis (chlamydia/gonococci are not usually detected on urine culture)
Vaginal infection/inflammation
Tuberculosis of the vaginal tract
Appendicitis
?fastidious organisms
What is pyuria?
Puss in urine
What are fastidious organisms?
Organisms that grow very slowly on culture
Who is most likely to have asymptomatic bacteriruia?
Elderly, in dwelling catheters
When are asymptomatic bacteriuria screen for and treated?
In pregnancy - untreated leads to higher risk for premature labour and pyelonephritis
What advice is given to treat UTI’s?
Increase fluid intake
Regular analgesia if painful
Address underlying disorders
How long are antibiotics prescribed to patients with UTI’s?
3 day course for uncomplicated UTI
5-7 day course for complicated lower UTI ie, pregnant, male, underlying disorders
Catheter sample urine (CSU) : only treat if systemically unwell
What antibiotics are given to treat uncomplicated UTIs?
Uncomplicated infections can be treated with nitrofurantoin, trimethoprim*, pivmecillinam or fosfomycin
3 day course as effective as 5 or 7 days
Why is it beneficial to give patients with uncomplicated simple cystitis a 3 day course of antibiotics?
Limiting prescription to 3 days reduces the selection pressure for resistance
Why is trimethoprim not always suitable to treat uncomplicated simple cystitis?
Up to 30% resistance in Leicestershire (2018-2019 data). Not suitable for those with a history of trimethoprim resistant UTI or received trimethoprim in last 3 months.
What antibiotics are used to treat a complicated cystitis?
Nitrofurantoin (first line) , trimethoprim*, pivmecillinam, fosfomycin or cefelexin (pregnancy) may be used – review susceptibility report
5-7 day course
How is pyelonephritis / septicaemia treated?
Pyelonephritis 7-10 days course
Use agent with systemic activity (NOT nitrofurantoin, fosfomycin)
Possibly IV initially unless good PO absorption and patient well enough/tolerating orally
◦ Co-amoxiclav
◦ Ciprofloxacin (effective as a 7 day course)
◦ Gentamicin NB IV only; nephrotoxic.
What patients might need prophylaxis for UTI’s?
> 3 episodes in one year despite behavioural and personal hygiene measures
No treatable underlying condition
What prophylaxis can be given to patients with recurrent UTI’s?
Low dose, long term antibiotics
Choice of antibiotics according to recent culture and susceptibility results (ie. trimethoprim or nitrofurantoin as a single nightly dose)
