Urinary tract infection pathology Flashcards
what is the presentation of a uti?
dysuria
frequency
smelly urine
why would a uti occur in yound children versus an eldery patient?
young - unwell failure to thrive
old - incontinent
renal blood flow is what percent of cardiac output?
20-25% of cardiac output
does urine output change with oral intake of fluid?
yes resorption of fluid is diminished if increase fluid intake increased urine output
do ureters store urine?
no have a continuous trickle of urine
how to ureters enter the bladder?
at an angle
increasing pressure from the bladder as it fills closes off ureter and stops reflux of urine
what are bacteriostatic properties od the urinary tract?
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
what is the exeption of the urinary tract that is sterile?
urinary tract exept terminal urethra
what will flush out many terminal urethral flora bacteria?
initial voiding
what are different types of urine specimin for culture?
- initial urine
- collect after initial void, patient voids stops mid stream discards urine then collects next volume (MSSU)
describe midstram specimin urine?
urethra flora will alwats grow in culture
no such thing as negative result
microbiology for culture under set conditions
bacteria multiply in log phase growth
quick way - dipslide method
what is the chance of contamination with MSSU culture?
105 per ml - <1:100 chance of contamination if asymptomatic – ie 99 times out of 100, 105 bacteria per ml represents infection – if specimen = MSSU
MSSU culture – 103 104
infection sometimes
if symptomatic probable that there is an infection
MSSU culture – 103 104 = 50 % chance of infection if no symptoms
MSSU culture – <103 =
ussually no infection
when is mssu difficult to collect?
in yound children and the elderly
what are problems with interpretation of urine cultures?
Some bacterial species are not normally present in terminal urethra/rectal flora and may be pathogenic at low colony numbers
what are the most common organisms that cause UTI’s?
Bacteria mostly = gut flora, especially E.coli
Viral infection rare
what is the route of infection most commonly?
almost always ascending
Infection in kidneys: usually infection has spread up from bladder infection
Upper urinary tract infection = more serious
what is infection of the urethra?
urethritis
what is infection of the bladder?
cystisis
what is infection of the kidney?
acute of chronic pylonephritis
what is infection of the ureter?
ureteritis
what are predisposing factors of a uti?
Stasis of urine
Pushing bacteria up urethra from below
Generalised predisposition to infection
what can cause stasis of urine?
Obstruction, whether congenital (presents in childhood) or acquired (adults).
Loss of ‘feeling’ (sensory loss) of full bladder - spinal cord/brain injury
what are causes of pushing bacteria up urethra from below?
Sexual activity in females
Catheterisation (and other urological procedures)
what are generalised predisposition to infection?
diabetes
at level of ureter what effect does obstruction have?
bilateral hydroureter
Bladder dilatation, bilateral hydroureter and bilateral hydronephrosis chronic renal failure
what does obstruction at level of renal pelvis on only one side cause?
unilatera; hydroureter
Unilateral hydroureter and unilateral hydronephrosis
what are the consequences of obstruction?
Proximal dilatation
Slowed urine flow Cannot flush out bacteria infection
Slowed urine flow sediments form calculous (stone) formation obstruction
Some bacterial infections predispose to calculous formation
what is the approach to obstruction in children?
Numerous renal tract abnormalities
Always investigate at 1st presentation and send to paediatric surgeons
Most important example = vesicoureteric reflux
what is the vesicoureteric reflux?
Vesicoureteric reflux – decreased angulation
what are comon causes of obstruction in males?
Benign Prostatic Hyperplasia (not a tumour) of prostate – functional and anatomical obstruction
what are comon causes of obstruction in women?
uterine prolapse
what effect does sexual activity have on lower urethral flora?
In females sexual activity tends to move lower urethral flora up the tract (back wall of urethra is just in front of vagina)
what is the predisposition to bacteria travelleding up in women?
Short urethra
Lack of prostatic bacteriostatic secretion
Closeness of urethral orifice to rectum
Sexual activity – (helps if void after intercourse)
Pregnancy – pressure on ureters and bladder
effect of catheterisation in utis?
Any instrumentation of urinary tract tends to move lower urethral flora up the tract
how can diabetes and chemotherapy lead to disposition to infection?
Glucose in urine
Poor function of WBC
what are acute complications of utis?
severe sepsis and septic shock
what are chronic complications of a uti?
Chronic damage to kidneys if repeated infections (chronic pyelonephritis) hypertension, chronic renal failure
Calculi obstruction Hydronephrosis hypertension, chronic renal failure
