Pathology of UTI Flashcards
Give the 3 main clinical features of a presentation of UTI
- Dysuria (pain on micturition)
- Increased frequency of micturition
- Smelly urine
Give 2 extra features if the patient presenting is very young
Unwell
Failure to thrive
Give 2 extra features if the patient presenting is very old
Incontinence
Off their feet
What occurs in a normal renal tract when oral intake of fluids increases?
Increased urine output due to diminished resorption of fluid
Do ureters store urine?
NO; they have a continuous trickle of urine
How does the bladder prevent reflux of urine?
Ureters enter bladder at an angle
Increasing pressure from bladder, as it fills, closes off ureter and stops reflux of urine
Describe the pH, osmolality and ammonia content of normal urine?
LOW pH
HIGH osmolality
HIGH ammonia (NH3)
What is the nature of prostatic secretions?
They are bacteriostatic
As well as free flow or urine (in well hydrated people), low pH, high osmolality, high ammonia and bacteriostatic prostatic secretions, what is the last bacteriostatic property of the normal urinary tract?
Contains anti-bacterial antibodies
How much of the urinary tract is sterile?
ALL; except terminal urethra which is subject to skin (perineal) and gut (rectal) flora
Why should urine specimen for culture be collected after initial void?
Initial void of urine will be heavily contaminated by terminal urethral floral bacteria
What is a MSSU?
Mid-Stream Specimen of Urine
= patient voids and stops mid-stream, discarding urine, then collects next volume of urine (will ensure urine is mostly sterile)
Is there such a thing as a negative result for an MSSU?
NO; urethral flora will always grow in culture as will be diminished but still present
In the dip slide method, what is the normal MSSU culture bacteria per ml value indicating infection?
10^5 per ml
1:100 chance of contamination if patient is asymptomatic
What is the MSSU culture bacteria per ml value indicating PROBABLE infection if the patient also has symptoms?
10^3 - 10^4 per ml
In a culture value of 10^3-10^4 per ml, when a patient has NO symptoms, what is the chance there is an infection?
50%
What is the culture value of bacteria per ml indicating no infection?
<10^3
Which demographic is an MSSU generally difficult to collect in?
Young children and elderly
What is the most common bacterial gut flora found in UTI?
E. coli
Is viral UTI common?
No, rare
What is the most common route of UTI?
Ascending (up urethra into bladder)
How do the kidneys usually become infected?
Usually infection has spread up from bladder infection (upper UTI = more serious)
Give the names for inflammation of each of: urethra, bladder, ureter, kidney
(first 3 does not necessarily mean infection; kidney usually does)
Urethra = URETHRITIS Bladder = CYSTITIS Ureter = URETERITIS Kidney = ACUTE/CHRONIC PYELONEPHRITIS
Give the 3 general predisposing factors for UTIs
- Stasis of urine
- Pushing bacteria up urethra from below
- Generalised predisposition to infection
Give 2 causes for stasis of urine
- OBSTRUCTION (congenital/acquired)
2. LOSS OF FEELING of full bladder (spinal cord/brain injury)
Give 2 causes of pushing bacteria up urethra from below
- Sexual activity in females
2. Catheterisation (and other urological procedures)
Give an example of a person predisposed to infection
A diabetic - macrophages do not function well in hypo + a lot of glucose in urine produces better environment for bacterial growth (any immune disease can predispose infection)
What does stasis of urine mean for bacteria that climb up the tract?
They do NOT get flushed out as in normal function
Describe how obstruction at the level of the urethra leads to chronic renal failure
- Upper urethral and bladder dilatation
- Bilateral hydroureter
- Bilateral hydronephrosis
- Prolonged hydronephrosis in both kidneys = CHRONIC RENAL FAILURE
What happens when obstruction only occurs at the level of the renal pelvis?
Unilateral hydroureter (providing obstruction is only in one kidney) Leading to unilateral hydronephrosis
Describe the triad of consequences of obstruction
Infection > Calculi > Obstruction > (all lead to one another)
How does stasis of urine cause calculus formation?
Slowed urine flow leads to formation of sediments and calculus (stone) formation - then leads to more infections, more dilatation and even more calculus formation
What should be done if a child presents with a UTI?
ALWAYS investigate at first presentation and send to paediatric surgeons - could indicate renal tract abnormality
Give the commonest renal tract abnormality causing UTI in children
Vesicoureteric reflux
Briefly describe the pathophysiology of vesicoureteric reflux
Decreased angulation of ureter as it enters bladder causing vesicoureteric reflux and eventually hydroureter
Give the commonest causes of obstruction in males, females and both sexes
Males = benign prostatic hyperplasia (function and anatomical obstruction - response as prostate ages) Females = uterine prolapse (particularly in women w lots of children) Both = tumours and calculi
What does decreased sensation to the bladder as a result of spinal cord/brain injury result in?
No sense of when to micturate and do not know to empty bladder completely, which leaves residual vol of urine in the bladder and causes stasis of urine
When does UTI incidence in females increase?
Around late teens/early twenties when woman becomes sexually active
Why do less males get UTIs?
Sexual activity predisposes females to them - but as males age they are more and more likely to get them (same even in females)
How does sexual activity cause UTI in females?
Tends to move lower urethral flora up the tract (back wall of urethra is just in front of the vagina)
UTIs in women not recently sexually active r more concerning
Give the 5 factors predisposing the female sex to UTIs
- 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 (and other urological procedures) move bacteria up the tract?
Any instrumentation of urinary tract tends to move urethral flora up the tract
How does diabetes predispose a person to infection?
Glucose in urine
Poor function of WBC
What are the acute complications of UTI?
Severe sepsis and septic shock
acute polynephritis - bacteria into blood - vessels in septic shock begin to dilate = septic shock
What are the chronic complications of UTI? (chronic damage; calculi)
- Chronic damage to kidneys if repeated infections (chronic polynephritis) -> hypertension, chronic renal failure
- Calculi -> obstruction -> hydronephrosis -> hypertension, chronic renal failure
What is the KEY QUESTION in UTI?
Why has the patient presented now?
