Pathology of UTI Flashcards
How does a UTI present
Dysuria (pain on micturition)
Frequent need to go to the toilet
Smelly urine
Urine output changes with what?
Oral intake of fluids
Resorption of fluid is diminished if increase fluid intake => increased urine output
How is the ureter opening in the bladder closed off?
Increasing pressure from bladder, as it fills, closes off ureter and stops reflux of urine. 1 way continous flow
Bacteriostatic properties of the urinary tract (4)
Free flow of urine through normal anatomy – assumes drinking enough fluids
Low pH, high osmolality, and high ammonia (NH3) content of normal urine
Prostatic secretions are bacteriostatic
Anti-bacterial antibodies
Which part of the urinary tract is not sterile?
The terminal urethra
Has skin and gut flora here
Where would you aspirate urine from to get a sterile sample?
The bladder (suprapubic)
What is a urinated specimen always contaminated with?
Terminal urethral flora
Why do you want a mid-stream urine sample ?
The initial urine is heavily contaminated. Mid-stream is less contaminated (but still present)
Patient voids and stops mid-stream, discarding urine, then collects next volume of urine = MSSU (mid-stream specimen of urine)
Because there is still a little bit of contamination in a MSSU, how do you tell contamination from real infection?
Microbiology for culture under set conditions
Bacteria multiply in log phase growth
=> 10^5 usually = infection (10^5 bacteria per ml)
=> 10^3-10^4 = sometimes infection - more likely if they have symptoms
=> less than 10^3 = usually no infection
In which age groups is it difficult to get a MSSU from?
Young children
Elderly
Microorganisms that cause UTI’s
Bacteria mostly = gut flora, especially E.coli
Viral infection rare
What’s the most common route of infection?
Ascending back into the bladder and if bladder becomes infected, up into the kidneys
an upper urinary tract infection = more serious
Names given to inflammation in: Urethra Bladder Ureter Kidney
Urethra – urethritis
Bladder – cystitis
Ureter – ureteritis
Kidney – acute pyelonephritis - if prolonged - chronic
Predisposing factors for a UTI (3)
Stasis of urine - Bacteria that do get higher up do not get flushed out
Pushing bacteria up urethra from below
Generalised predisposition to infection
What can cause stasis of urine? (2)
Obstruction, whether congenital (presents in childhood) or acquired (adults).
Loss of ‘feeling’ of full bladder - spinal cord/brain injury
What can cause bacteria to be pushed up the urethra from below?
Sexual activity in females
Catheterisation (and other urological procedures)
What is an example of a generalised predisposition to infection?
Diabetes - glucose in urine
poor function of WBC’s
What obstruction can occur at the level of the urethra?
Bladder dilatation
Bilateral hydroureter (dilatation)
Bilateral hydronephrosis (one or both kidneys become stretched and swollen as a result of a build-up of urine inside them)
All of these can lead to chronic renal failure
What obstruction can occur at the level of the renal pelvis on 1 side only?
Unilateral hydroureter
Unilateral hydronephrosis
How does obstruction lead to infection?
Proximal dilatation
Slowed urine flow
=> Cannot flush out bacteria => infection
How does obstruction lead to kidney stone formation
Slowed urine flow => sediments form => Stone forms
which causes obstruction => more dilatation, more infections and increased stone formation.
Some bacterial infections predispose to calculous formation
The triad of obstruction consequences
Infection causes calculin formation which causes obstruction which causes infection and so on
What is Vesicoureteric reflux?
When urine flows backward from the bladder into the ureters/kidneys caused by decreased angulation of the ureters at their insertion at the bladder
Common in children
What is hydroureter?
Dilatation of the ureter
Common cause of obstruction in adults
Men = Benign Prostatic Hyperplasia (not a tumour) of prostate – functional and anatomical obstruction
Women = uterine prolapse
Both = tumours and calculi
How might someone not realise their bladder is full?
Decreased sensation => no sense of when to micturate and do not know to empty bladder completely => leave urine in bladder (high residual volume) => stasis of urine
Predisposing factors in females?
Short urethra
Lack of prostatic bacteriostatic secretion
Closeness of urethral orifice to rectum
Sexual activity – (helps if void (pee) after intercourse)
Pregnancy – pressure on ureters and bladder
Acute complication of UTI
Severe sepsis and septic shock
Chronic complications of UTI
Chronic damage to kidneys if repeated infections (chronic pyelonephritis) =>
hypertension, chronic renal failure
Calculi => obstruction => Hydronephrosis => hypertension, chronic renal failure
