Urinary Tract Infection (UTI) Flashcards
What is dysuria?
Pain on micturition
How does a UTI present?
Dysuria
Frequency
Smelly urine
Very young: unwell, failure to thrive
Very old: incontinence, off their feet
Why do the ureters enter the bladder at an angle?
Enter bottom of bladder at angle so that increasing pressure from bladder as it fills -> closes off ureter and stops reflux of urine
What are the bacteriostatic properties of the normal urinary tract?
Free flow of urine through normal anatomy- assumes drinking enough fluids
Low pH, high osmolarity, and high ammonia (NH3) content of normal urine
Prostatic secretions are bacteriostatic
Anti-bacterial antibodies
How much of the urinary tract is normally sterile?
All urinary tract except for terminal urethra
How can you bypass the terminal urethra to take a clean sample of urine?
Suprapubic aspirate of urine
-Needle straight into bladder
Why do we take a midstream sample (or suprapubic aspirate) for urine MC&S?
Urinated sample will always be contaminated by terminal urethral flora
Initial void will wash terminal urethra -> sample taken after will be more sterile avoiding false positives
Explain how you carry out a mid stream sample
Patient voids and stops mid-stream, discarding urine, then collects next volume of urine = MSSU (midstream specimen of urine
Can you ever get rid of all terminal urethral flora by a MSSU?
No
Urethral flora will be diminished by always present
Will always grow in culture so never a negative result
What does MSSU stand for?
Mid Stream Specimen Urine
How do you tell contamination from real infection in MSSU?
Microbiology for culture under set conditions
Bacteria multiply in log phase growth
10^5 per ml
A MSSU culture result of 10^3 would indicate what?
10^3 and 10^4 need to be interperated clinically:
- If symptomatic probably infection
- If asymptomatic 50% infection
In which populations is an MSSU difficult to collect?
Young children and elderly
What are the problems with interpretation of urine culture?
Some bacterial species are not normally present in terminal urethra/rectal flora and may be pathogenic at low colony numbers
What micro-organisms cause UTI?
Bacteria mostly = gut flora, especially E. coli
Viral infection rare
What is the route of infection in UTI?
Almost always ascending from terminal urethra
Infection in kidneys has usually spread up from bladder infection
Which is more serious:
Upper UTI or Lower UTI?
Upper UTI more serious
What is urethritis?
INFECTION of urethra
Usually itis = inflammation but here almost always infection
What is cystitis?
Inflammation/infection of bladder
What is ureteritis?
Infection of the ureter
What is acute pyelonephritis?
Kidney infection/ inflammation
If recurrent/ prolongued infection -> chronic pyelonephritis
What are the predisposing factors for a UTI?
- Stasis of urine
- Pushing bacteria up urethra from below
- generalised predisposition to infection
How can stasis of urine come about?
- Obstruction, whether congenital (presents in childhood) or acquired (adults).
- Loss of “feeling” of full bladder - spinal cord/ brain injury
How can pushing bacteria up urethra from below come about?
Sexual activity in females
Catheterisation (and other urological procedures)
What may cause a generalised predisposition to infection?
e.g. Diabetes
How does obstruction of the urethra effect the urinary tract?
Upper urethral and bladder dilatation
If this continues -> bilateral hydroureter -> bilateral hydronephrosis -> chronic renal failure
What does unilateral hydroureter indicate as opposed to bilateral hydroureter?
Unilateral = obstruction above bladder
Bilateral = obstruction below bladder
What are the consequences of obstruction?
Proximal dilatation
Slowed urine flow -> cannot flush out bacteria -> infection
Slowed urine flow -> sediments form -> calculous formation -> obstruction -> repeat cycle
What is the obstruction triad?
Infection -> calculi -> obstruction -> infection etc
What is obstruction in children usually caused by?
There are numerous renal tract abnormalities
-Usually one of these
Always investigate at first presentation and send to paediatric surgeons
What is the most important renal tract abnormality for obstruction in children?
Vesicoureteric reflux
What is vesicoureteric reflux?
Normally ureters insert into bladder at angle
Decreased angulation in vesicoureteric reflux -> ureter isnt closed off by increasing bladder pressure -> reflux -> hydroureter -> hydronephritis
What are common causes of obstruction in adults?
Males - Benign Prostatic Hyperplasia (NOT a tumour) -> functional and anatomical obstruction
Females - Uterine prolapse
Both sexes - Tumours and calculi
What is the residual bladder volume?
Volume of fluid left in bladder after urination
You want this to be as small as possible to prevent static urine
How does spinal cord/ brain injury predispose to UTI?
Decreased sensation -> no sense of when to micturate and do not know how to empty bladder completely -> leave urine in bladder -> high residual volume -> stasis of urine
How does female sexual activity tend to lead to UTI?
Move lower urethral flora up the tract (back wall of urethra is just in front of vagina)
Why are females more predisposed to UTI?
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
How does catheterisation predispose to UTI?
Any instrumentation of urinary tract tends to move lower urethral flora up the tract
How does diabetes predispose to UTI?
Glucose in urine
Poor function of WBC
What are the acute complications of UTI?
Severe sepsis and septic shock
What are the chronic complications of UTI?
Chronic damage to kidneys if repeated infections (chronic pyelonephritis) -> hypertension, chronic renal failure
Calculi -> obstruction -> hydronephrosis -> hypertension, chronic renal failure
