Pathology of Urinary Tract Infection Flashcards
What is the common presentation of a UTI?
Dysuria (pain on micturition), frequency and smelly urine
Very young - unwell and failure to thrive
Ver old - incontinence and off their feet
What is renal blood flow equal to?
20-25% cardiac output
How does urine output change with oral intake of fluids?
Reabsorption of fluid is diminished if increased fluid intake which increases urine output
Does the ureters store urine?
No they do not store but have continuous trickle of urine
Explain the importance of the ureter entering the bladder at an angle
Increasing pressure from bladder as it fills - closes off ureter and stops the reflux of urine
What are some bacteriostatic properties of the normal urinary tract?
Free flow of urine in normal anatomy - assume enough fluids
Low pH, high osmolarity, and high ammonia content of urine
Prostatic secretions - Men
Antibacterial antibodies
Which part of the normal renal tract is not sterile?
Terminal urethra
Perineal skin and gut flora
What is a urinated specimen always contaminated with?
Terminal urethra flora
Explain a collection of urine after initial void
Patient voids and stops mid-stream, discarding urine, then collects next volume of urine - MSSU (mid-stream specimen of urine)
This has far less bacteria from terminal urethra but still present
Can there be a negative result in an MSSU?
No such thing as a negative result
How is an MSSU analysed?
Microbiology of culture under set conditions
Bacteria multiply in log phase growth
Can do a dip slide method - look at bacteria colonies
What value in MSSU culture usually means infections?
10^5 per ml
What is 10^3 to 10^4 per ml on MSSU culture?
Infection sometimes
Probable infection if there are symptoms
50% chance if no symptoms
What is less than 10^3 per ml on MSSU mean?
Usually no infection
What is a problem with interpretation of urine culture?
Some bacterial species are not normally present in the terminal urethra/ rectal flora and may be pathogenic at low colony numbers
What are the common micro-organisms which cause UTI?
Bacteria mainly - gut flora, esp. E.coli
Viral infection is rare
What is the route of infection in UTI?
Usually always ascending
Infection from kidneys usually from bladder infection
Upper UTI is more serious
What are inflammation of renal tract parts called?
Urethritis, cystitis, urethritis, and acute pyelonephritis
If recurrent/ prolonged then chronic pyelonephritis
What are some predisposing factor of UTI?
Stasis of urine
Pushing bacteria up urethra from below
Generalised predisposition to infection - diabetes
What can cause stasis of urine?
Obstruction - congenital or acquired
Loss of feeling (sensory loss) of full bladder
What can cause pushing of bacteria up urethra from below?
Sexual activity in females
Catheterisation
What can be the result of obstruction at level of urethra?
Upper urethral and bladder dilatation
Then if this continues - bilateral hydroureter (ureteric dilatation)
Then if continues - bilateral hydro-nephrosis - chronic renal failure
What happens when there is obstruction of renal pelvis on 1 side only?
Unilateral hydroureter
If continues then get unilateral hydro-nephrosis
So still have a normal kidney at one side
What are the consequences of obstrcution?
Proximal dilatation
Slowed urine flow - can’t flush out bacteria so infection
Also slowed urine flow - sediments form and then calculous form leading to obstruction - more infections, dilatation and calculous forming
What is the triad of obstruction consequences?
Infection, calculi and obstruction
Explain obstruction in children
Numerous renal tract abnormalities
Always investigate at 1st presentation and send to paediatric surgeons
Most important - vesicoureteric reflux
Describe vesicourecteric reflux
Decreased angulation - so can get urine fluxing backwards even when bladder is full
Then get hydroureter
What are common causes of obstruction in adults?
Men - benign prostatic hyperplasia of prostate - functional and anatomical obstruction
Women - uterine prolapse
Both sexes - tumours and calculi
How does spinal cord/ brain injury cause a predisposition for UTI?
Decreased sensation - no sense to micturate and not know when empty bladder completely so leave urine in bladder so stasis of urine
How does diabetes cause a predisposition to UTIs?
Glucose in urine and poor function of WBCs
What is the predisposition of UTI for female sex?
Short urethra, lack of prostatic bacteriostatic secretion, closeness of urethral orifice to rectum, sexual activity and pregnancy
What is an acute complication of UTI?
Severe sepsis and septic shock
What are chronic complications of UTI?
Chronic damage to kidneys if repeated infections (chronic pyelonephritis) - hypertension and chronic renal failure
Calculi - obstruction - hydro-nephrosis - hypertension and chronic renal failure
