Pathology of UTIs Flashcards
UTI presentation?
Dysuria
Frequency
Urine will smell
In elderly - incontinence, delirium
In very young - unwell, failure to thrive
How much of CO is renal blood flow?
20-25%
Do ureters store urine?
No - they have a continuous trickle of urine
Ureters enter the bladder at a BLANK this is significant because?
Angle
Significant as when bladder fills, the pressure inside closes off the ureter and stops reflux of urine
Normal urine pH, osmolality and ammonia contents ?
Low pH
High osmolality
High ammonia
Prostatic secretions are…which means…
Bacteriostatic - biological or chemical agent that stops bacteria from reproducing
Does urine contain anti-bacterial antibodies?
Yeah
Is the urinary tract ALL sterile?
No - most is except the terminal urethra
What significance does the terminal urethra not being sterile have on urine sample collection?
Sample must be collected mid-flow as the initial flow will be contaminated with the terminal urethra’s bacteria
The initial flow diminishes the urethras bacteria, doesn’t eliminate it
What is a MSSU?
mid stream specimen of urine
How do we tell if a MSSU is contaminated or if there is a real infection?
Sent to microbiology for culture under set conditions
Bacteria multiply in a log phase growth
What is a faster way to read a MSSU and to determine if it is contamination or infection?
A dip slide method - incubated for 24 hours at 37 degrees
A culture reading of 10^5 usually indicates infection
10^3 or ^4 suggests an infection probable if symptoms but if NO symptoms a 50% chance it isn’t an infection
If the culture shows less than 10^3?
Won’t be an infection
Issues with MSSU?
Hard to collect in young and elderly
Some bacteria are not normally preent in terminal urethra/rectal flora and may be pathogenic at low numbers BUT won’t be picked up on with a dip slide method
Microorganisms that cause UTIs?
Bacteria - usually gut flora - like E.coli
Viral infection rare
Route of infection?
Almost always ascending
An infection in the kidney’s would have spread from a bladder infection
Is an upper or lower UTI more serious?
Upper
Infection in urethra, bladder, ureter and kidney are called what respectively?
Urethra - urethritis
Bladder - cystitis
Ureter - ureteritis
Kidney - acute pyelo-nephritis BUT if prolonged - chronic pyelonephritis
What are the predisposing factors for a UTI?
- Stasis of urine
- Pushing bacteria up from urethra below
- Generalised predisposition to infection
What can cause stasis of urine?
Obstruction - congenital or acquired
Spinal cord/brain injury - losing the feeling of a full bladder
Why does stasis of urine cause a UTI?
Bacteria that get higher up in the tract are not flushed out
What does obstruction at the level of the ureter cause?
Upper urethral and bladder dilatation eventually leading to bilateral hydroureter
What can bilateral hydroureter lead to?
Bilateral hydronephrosis (swelling of kidney) leading to chronic renal failure
What happens if obstruction is at level of renal pelvis?
Unilateral hydroureter (lower ureter will be fine) and unilateral hydronephrosis
Consequences of obstruction?
Proximal dilatation
Low urine flow means bacteria isn’t flushed out = infection
Low urine flow also means sediments form leading to calculous formation and further obstruction = further infections
What should be done if a child presents with obstruction?
Always investigate asap and send to paediatric surgeons
Most important obstruction cause in kids?
Vesicoureteric reflux - when angle of ureters into bladder is decreased and = a hydroureter
Common causes of obstruction in men?
Benign prostatic hyperplasia (not a tumour)
Is a functional and anatomical obstruction
Common causes of obstruction in women?
Uterine prolapse
Common causes of obstruction not specific to 1 sex?
Tumours and calculi
Why does a spinal injury that reduced sensation of when bladder is full cause stasis of urine
No sense of when to micturate and do not know how to empty bladder fully and leave urine in bladder = stasis of urine
What can cause bacteria to be pushed up the urinary tract?
Sexual activity in women
Catheterisation
Who would have a generalised predisposition to infection?
Diabetics due to glucose in urine and poor function of WBCs
Acute complications of UTIs?
Sepsis and septic shock
Chronic complications of UTIs?
Chronic damage to kidneys if repeated infections
Calculi = obstruction = hydronephrosis
All this leads to hypertension and chronic renal failure
