Pathology of UTIs Flashcards
What % of CO makes up renal blood flow?
20-25%
How do people present with UTIs?
- Dysuria (pain on micturition), frequency, smelly urine
- But: very young – unwell, failure to thrive
- Very old – incontinence, off their feet
List the bacteriostatic properties of 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 terminal urethra commonly infected with?
Terminal urethra can be infected with skin (perineal) and gut (rectal) flora
What urine should be used when testing for UTIs?
Mid stream specimen of urine (MSSU)
What is a quick way to test for UTIs?
Dip slide method
What bacteria count indicates a definite infection when analysing MSSU via a dip slide?
10^5 usually = infection: 105 per ml represents <1:100 chance of contamination if asymptomatic – i.e. 99 times out of 100, 105 bacteria per ml represents infection if specimen is MSSU
What bacteria count indicates a possible infection when analysing MSSU via a dip slide?
10^3 - 10^4 = infection sometimes. Probable infection if have symptoms, and 50 % chance of infection if no symptoms.
What bacteria count indicates an unlikely infection when analysing MSSU via a dip slide?
< 10^3 = usually no infection
What is an issue with MSSU?
Can be difficult to collect in the young or the elderly
What is an issue with the sip slide method of analysing MSSU?
Some bacterial species are not normally present in terminal urethra/rectal flora and may be pathogenic at low colony numbers, and therefore be missed by dip slide
Describe the route of infection in UTIs
Usually ascending
List the names of the inflammatory conditions affecting each component of the urinary system
o Urethra – urethritis
o Bladder – cystitis (inflammation of bladder wall)
o Ureter – ureteritis
o Kidney – acute or chronic pyelonephritis
What are some predisposing factors for UTIs?
- Stasis of urine
- Pushing bacteria up urethra from below
- Generalised predisposition to infection e.g. diabetes
Female sex
What can cause stasis of the urine?
o Obstruction, whether congenital (presents in childhood) or acquired (adults).
o Loss of ‘feeling’ of full bladder - spinal cord/brain injury
What can push up bacteria into the urinary tract to cause infection?
- Sexual activity in females
* Catheterisation (and other urological procedures)
What are some common consequences of obstruction?
Infection and calculi formation
What causes obstruction of urine in children?
- Numerous renal tract abnormalities
- Always investigate at 1st presentation and send to paediatric surgeons
- Most important eg = vesicoureteric reflux
What is vesicoureteric reflux?
Vesicoureteric reflux: decreased angulation of insertion of ureters into bladder causes backwards flow of urine from the bladder to the kidneys, causing hydroureter. About 10% of children have VUR
What are some common causes of obstruction in adults?
- Men – Benign Prostatic Hyperplasia (not a tumour) of prostate – functional and anatomical obstruction by compression of the urethra
- Women – uterine prolapse
- Both sexes – tumours and calculi
How do spinal cord or brain injuries cause stasis of urine?
Decreased sensation leads to no sense of when to micturate and do not know to empty bladder completely. This leaves urine in bladder following urination (high residual volume) and stasis of urine
Why is the female sex more predisposed to UTI development?
- 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
Give an example of a cause of generalised predisposition to UTIs
Diabetes
- Glucose in urine
- Poor function of WBC
What are some complications associated with UTIs?
Acute complications:
o Severe sepsis and septic shock
Chronic complications:
o Chronic damage to kidneys if repeated infections (chronic pyelonephritis) - hypertension, chronic renal failure
o Calculi - obstruction - Hydronephrosis - hypertension, chronic renal failure
