Pathology of Urinary Tract Infections Flashcards
What is the presentation of UTI?
- Dysuria (pain on micturition), frequency, smelly urine
- But in very young
- Unwell, failure to thrive
- In very old
- Incontinence, off their feet
What does UTI stand for?
Urinary tract infection
What is the medical term for pain on micturition?
Dysuria
What percentage of cardiac output is renal blood flow?
20-25%
What does CO stand for?
Cardiac output
What can urine output vary with?
Urine output changes with oral intake of fluids:
- Resorption of fluid is diminished if increase fluid intake causing increased urine output
Do the uterters have continuous trickle of urine or do they store urine?
Ureters have continuous trickle of urine, they do not store urine and they enter the bladder at an angle
Do the ureters enter the bladder perpendicular or at an angle?
At an angle
What happens to the ureters as the bladder fills?
They increase pressure of bladder as it fills, closing off ureter and stops reflux of urine
So the flow of urine is a one way continuous flow until the bladder is full
What are some bacteriostatic properties of the urinary tract?
- Free flow of urine through normal anatomy
- Low pH, high osmolarity and high ammonia (NH3) content of normal urine
- Prostatic secretions are bacteriostatic (bacteriostatic agent is a biological or chemical agent that stop bacteria from reproducing)
- Anti-bacterial antibodies
What is a bacteriostatic agent?
A biological or chemical agent that stop bacteria from reproducing
Is the urinary tract sterile or non-sterile?
The whole urinary tract, except for the terminal urethra, is sterile
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Do urinated specimen contain any bacteria?
Urinated specimen is always contaminated by terminal urethra flora
Initial voiding will flush out many terminal urethral floral bacteria
Before taking a urine sample, what should be done to flush out many terminal urethral floral bacteria?
Initial voiding will flush out many terminal urethral floral bacteria
How is a urine sample collected without the contamintion of flora?
Initial urine is heavily contaminated, so collect after initial void:
- Patient voids and stops mid-stream, discarding urine then collects next volume of urine
- Known as mid-stream specimen of urine (MSSU)
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What does MSSU stand for?
Mid-stream specimen of urine
What is the kind of urine sample known as where the patient voids first to get rid of a lot of flora bacteria?
Mid-stream specimen of urine (MSSU)
In MSSU is the urethral flora present?
In a MSSU the urethral flora is diminished but always present, and will then grow in culture:
- Therefore is no such thing as a negative result
What is a quick method of performing MSSU culture?
Quick way to perform MSSU culture is the dip slide method (but usually send for formal microbiology culture
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How is a urine sample normally analysed?
Formal microbiology culture, but sometimes dip slide method can be performed which is quicker
What kind of growth do bacteria display?
Multiply in log phase growth
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What are the boundaries of amount of bacteria and likelyhood of infection in MSSU?
- 105/ml is usually infection
- <1/100 chance of contamination if asymptomatic
- 103 to 104/ml is an infection sometimes
- Probable infection if have symptoms
- 50% chance of infection if no symptoms
- <103 usually means no infection
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What does a bacteria concentration of 105 normally indicate?
- 105/ml is usually infection
- <1/100 chance of contamination if asymptomatic
What does a bacteria concentration of 103-104/ml usuall indicate?
- 103 to 104/ml is an infection sometimes
- Probable infection if have symptoms
- 50% chance of infection if no symptoms
What does a bacteria concentration of <103 indicate?
Usually means no infection
MSSU is difficult to collect in who?
Yound children and elderly
Why can there sometimes be a problem with interpretation in a urine specimen?
- Some bacterial species are not normally present in terminal urethra/rectal flora and may be pathogenic at low colony numbers
What bacteria often causes UTI?
- Gut flora, especially E. Coli
Do viruses often cause UTI?
Viral infection is rare
Is route of infection usually ascending or descending?
Almost always ascending
Where has infection in the kidneys usually come from?
Spread from bladder
What are the two kinds of UTI?
Upper urinary tract infection
Lower urinary tract infection
Is upper or lower urinary tract infection more serioues?
Upper urinary tract infection
What does a urinary tract infection lead to?
Infection leads to inflammatory response:
- Urethritis in urethra
- Cystitis in bladder
- Urethritis in ureter
- Acute pyelonephritis in kidney
- Chronic pyelonephritis in kidney if recurrent/prolonged infection
What is inflammation in the urethra known as?
Urethritis
What is inflammation in the bladder known as?
Cystitis
What is inflammation in the ureter known as?
Ureteritis
What is inflammation in the kidney known as?
Acute pyelonephritis
Or chronic pyelonephritis if recurrent/prolonged infection
What are the different categories of predisposing factors to UTI?
- Stasis of urine
- Obstruction
- Whether congenital (presents in childhood) or acquired (adults)
- Loss of ‘feeling’ of full bladder
- Spinal cord/brain injury
- Obstruction
- Pushing bacteria up urethra from below
- Sexual activity in females
- Catheterisation (and other urological procedures)
- Generalised predisposition to infection
- Diabetes
What are the 2 different kinds of stasis of urine?
- Obstruction
- Whether congenital (presents in childhood) or acquired (adults)
- Loss of ‘feeling’ of full bladder
- Spinal cord/brain injury
What can push bacteria up the urethra from below?
- Sexual activity in females
- Catheterisation (and other urological procedures)
What is an example of a general predisposition to urinary tract infection?
Diabetes
What are consquences of obstruction in the urinary tract?
- Proximal dilation
- Slow urine flow
- Meaning cannot flush out bacteria and causing infection
- Also allows sediments to form, causing calculous (stone) formation cause further obstruction, and this obstruction causes more dilation, more infections and increased calculous formation
Why does obstruction lead to UTI?
- Slow urine flow
- Meaning cannot flush out bacteria and causing infection
- Also allows sediments to form, causing calculous (stone) formation cause further obstruction, and this obstruction causes more dilation, more infections and increased calculous formation
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How are the consequences of obstruction a triad?
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What should you do when children present with obstruction of the urinary tract?
- Numerous renal tract abnormalities
- Always investigate at 1st presentation and send to paediatric surgeons
- Most important example is vesicoureteral reflux (condition which urine flows retrograde, or backwards from the bladder into the ureters/kidneys)
- Causes decreased angulation of ureter into bladder
- Leads to hydroureter
What is the most important example of urinary tract obstruction in children?
- Most important example is vesicoureteral reflux (condition which urine flows retrograde, or backwards from the bladder into the ureters/kidneys)
- Causes decreased angulation of ureter into bladder
- Leads to hydroureter
What is vesicoureteral reflux?
Condition which urine flows retrograde, or backwards from the bladder into the ureters/kidneys
What are the consequences of vesicoureteral reflux?
- Causes decreased angulation of ureter into bladder
- Leads to hydroureter (dilation of the ureter)
What is the medical term for dilation of the ureter?
Hydroureter
What are some common causes of urinary tract obstruction in adults?
- Men
- Benign prostatic hyperplasia (not a tumour)
- Functional and anatomical obstruction
- Basically enlarged prostate surrounding urethra
- Benign prostatic hyperplasia (not a tumour)
- Woman
- Uterine prolapse
- Both sexes
- Tumours and calculi (kidney stones)
How can a spinal cord/brain injury impact the urinary tract?
Decreased sensation causes no sense of when to micturate and do not know to empty the bladder complete:
- Leaving urine in bladder (high residual volume) causing stasis of urine
How can sexual activity cause a UTI in a female?
In females, sexual activity tends to move lower urethral flora up the tract (back wall of urethra is just in front of vagina
What are some predisposing factors for UTi due to pushing bacteria up the urethra in woman?
- 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
Why can diabetes lead to UTI?
- Glucose in urine
- Poor function of WBC
What is the cause of urinary tract infections usually dependent on?
Age
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What are some complications of UTI?
- Acute
- Severe sepsis and septic shock
- Chronic
- Chronic damage to kidneys if repeated infections (chronic pyelonephritis) causing hypertension and chronic renal failure
- Calculi causing obstruction, then hydronephrosis, then hypertension and chronic renal failure
What are complications of acute UTI?
- Severe sepsis and septic shock
What are consequences of chronic UTI?
- Chronic damage to kidneys if repeated infections (chronic pyelonephritis) causing hypertension and chronic renal failure
- Calculi causing obstruction, then hydronephrosis, then hypertension and chronic renal failure