Pathology of UTI

Question 1

How does a UTI present

Answer 1

Dysuria (pain on micturition)

Frequent need to go to the toilet

Smelly urine

Question 2

Urine output changes with what?

Answer 2

Oral intake of fluids

Resorption of fluid is diminished if increase fluid intake => increased urine output

Question 3

How is the ureter opening in the bladder closed off?

Answer 3

Increasing pressure from bladder, as it fills, closes off ureter and stops reflux of urine. 1 way continous flow

Question 4

Bacteriostatic properties of the urinary tract (4)

Answer 4

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

Question 5

Which part of the urinary tract is not sterile?

Answer 5

The terminal urethra

Has skin and gut flora here

Question 6

Where would you aspirate urine from to get a sterile sample?

Answer 6

The bladder (suprapubic)

Question 7

What is a urinated specimen always contaminated with?

Answer 7

Terminal urethral flora

Question 8

Why do you want a mid-stream urine sample ?

Answer 8

The initial urine is heavily contaminated. Mid-stream is less contaminated (but still present)

Patient voids and stops mid-stream, discarding urine, then collects next volume of urine = MSSU (mid-stream specimen of urine)

Question 9

Because there is still a little bit of contamination in a MSSU, how do you tell contamination from real infection?

Answer 9

Microbiology for culture under set conditions

Bacteria multiply in log phase growth

=> 10^5 usually = infection (10^5 bacteria per ml)

=> 10^3-10^4 = sometimes infection - more likely if they have symptoms

=> less than 10^3 = usually no infection

Question 10

In which age groups is it difficult to get a MSSU from?

Answer 10

Young children

Elderly

Question 11

Microorganisms that cause UTI’s

Answer 11

Bacteria mostly = gut flora, especially E.coli

Viral infection rare

Question 12

What’s the most common route of infection?

Answer 12

Ascending back into the bladder and if bladder becomes infected, up into the kidneys

an upper urinary tract infection = more serious

Question 13

Names given to inflammation in:
Urethra
Bladder
Ureter
Kidney

Answer 13

Urethra – urethritis
Bladder – cystitis
Ureter – ureteritis
Kidney – acute pyelonephritis - if prolonged - chronic

Question 14

Predisposing factors for a UTI (3)

Answer 14

Stasis of urine - Bacteria that do get higher up do not get flushed out

Pushing bacteria up urethra from below

Generalised predisposition to infection

Question 15

What can cause stasis of urine? (2)

Answer 15

Obstruction, whether congenital (presents in childhood) or acquired (adults).

Loss of ‘feeling’ of full bladder - spinal cord/brain injury

Question 16

What can cause bacteria to be pushed up the urethra from below?

Answer 16

Sexual activity in females

Catheterisation (and other urological procedures)

Question 17

What is an example of a generalised predisposition to infection?

Answer 17

Diabetes - glucose in urine

poor function of WBC’s

Question 18

What obstruction can occur at the level of the urethra?

Answer 18

Bladder dilatation

Bilateral hydroureter (dilatation)

Bilateral hydronephrosis (one or both kidneys become stretched and swollen as a result of a build-up of urine inside them)

All of these can lead to chronic renal failure

Question 19

What obstruction can occur at the level of the renal pelvis on 1 side only?

Answer 19

Unilateral hydroureter

Unilateral hydronephrosis

Question 20

How does obstruction lead to infection?

Answer 20

Proximal dilatation

Slowed urine flow
=> Cannot flush out bacteria => infection

Question 21

How does obstruction lead to kidney stone formation

Answer 21

Slowed urine flow => sediments form => Stone forms
which causes obstruction => more dilatation, more infections and increased stone formation.

Some bacterial infections predispose to calculous formation

Question 22

The triad of obstruction consequences

Answer 22

Infection causes calculin formation which causes obstruction which causes infection and so on

Question 23

What is Vesicoureteric reflux?

Answer 23

When urine flows backward from the bladder into the ureters/kidneys caused by decreased angulation of the ureters at their insertion at the bladder

Common in children

Question 24

What is hydroureter?

Answer 24

Dilatation of the ureter

Question 25

Common cause of obstruction in adults

Answer 25

Men = Benign Prostatic Hyperplasia (not a tumour) of prostate – functional and anatomical obstruction

Women = uterine prolapse

Both = tumours and calculi

Question 26

How might someone not realise their bladder is full?

Answer 26

Decreased sensation => no sense of when to micturate and do not know to empty bladder completely => leave urine in bladder (high residual volume) => stasis of urine

Question 27

Predisposing factors in females?

Answer 27

Short urethra

Lack of prostatic bacteriostatic secretion

Closeness of urethral orifice to rectum

Sexual activity – (helps if void (pee) after intercourse)

Pregnancy – pressure on ureters and bladder

Question 28

Acute complication of UTI

Answer 28

Severe sepsis and septic shock

Question 29

Chronic complications of UTI

Answer 29

Chronic damage to kidneys if repeated infections (chronic pyelonephritis) =>
hypertension, chronic renal failure

Calculi => obstruction => Hydronephrosis => hypertension, chronic renal failure