Pathology of urinary tract infection

Question 1

Give a brief description of the common presentation for a UTI

What features may also be present in:

a) elderly patients
b) very young patients

Answer 1

Dysuria - pain on micturition

Altered frequency

Smelly urine

Elderly - incontinence, off their feet

Young - unwell, failure to thrive

Question 2

What % of cardiac output goes through kidneys?

Answer 2

20-25%

Question 3

In normal health - how does urine pass through the ureters to the bladder?

Answer 3

A continuous trickle

urine is not stored in the ureters - ie never stationary (in health)

Question 4

Describe how the ureters are closed at their entrance to the bladder

Answer 4

The ureters enter the bladder at an angle

As pressure from the bladder increases (ie as it fills up) - the ureteric orifice is closed off

The fact it enters at an angle is important to allow this

Question 5

Describe the bacteriostatic properties of the urinary tract

Answer 5

Low pH, high osmolality, and high ammonia (NH3) content in normal urine

Prostatic secretions are bacteriostatic - meaning they prevent bacteria from replicating btw

There are also anti-bacterial antibodies

Question 6

Is the urinary tract sterile or riddled?

Answer 6

Urinary tract, except for terminal urethra, is sterile

Question 7

What types of urine specimens are available - and which are sterile or not?

Answer 7

Urinated samples - always contaminated (even if MSSU) with terminal urethral flora

Suprapubic samples - are sterile in health

Question 8

What is MSSU?

Answer 8

Midstream specimen of urine (MSSU)

Patient voids and stops mid-stream, discarding urine, then collects next volume of urine

Initial voiding gets rid of a lot of the flora so provides a less contaminated sample

Question 9

What MSSU sample results would indicate a UTI?

Answer 9

10^{<strong>5</strong>} - Pretty much always = infection

10³ - 10⁴ - Probably a UTI if symptomatic

< 10³ - usually not a UTI

Question 10

What organisms cause UTIs?

Answer 10

Bacteria (esp Gut flora) mostly - most commonly E.coli

Others are Klebsiella and Proteus spp

Question 11

What are the specific types of UTIs?

What is the route of infection?

Answer 11

Urethra = urethritis

Bladder = cystitis

Ureter = ureteritis

Kidney = acute pyelonephritis

Route of infection is usually ascending the urinary tract - ie Upper UTIs usually secondary to lower UTIs

Question 12

For Upper and Lower urinary tract infections - which is:

a) More serious?
b) More likely to be primary?

Answer 12

Upper UTIs are more serious

Lower UTIs are more likely to happen and more likely to be primary.

Route of infection is ascending the urinary tract so Lower UTIs often happen by themselves - whereas Upper UTI’s dont tend to happen without a lower UTI

Question 13

What happens if there is recurrent and prolonged infection of the kidneys?

Answer 13

chronic pyelonephritis

Question 14

What histological signs are there of cystitis?

Answer 14

Inflammation of the bladder wall

Question 15

What histological signs are there of acute pyelonephritis?

Answer 15

Neutrophils in renal tubules

Question 16

What are the predisposing factors (basic causes) UTIs?

Answer 16

Stasis of urine

Pushing bacteria up urethra from below

Generalised predisposition to infection

Question 17

What can cause stasis of urine - thus leading to a UTI?

Answer 17

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

Loss of ‘feeling’ (sensory loss) of full bladder - spinal cord/brain injury

Question 18

What are the causes of UTIs that involve physical pushing of bacteria up the urinary tract?

Answer 18

Catheterisation

Sex (females only)

Question 19

How does obstruction affect the structures of the urinary tract?

Answer 19

Obstruction is a cause of UTIs

Question 20

What causes only unilateral hydroureter and hydronephrosis?

What anatomical feature makes this often happen?

Answer 20

Obstruction of a single ureter

Often happens at the site of constrictions in the ureter

Question 21

What are the consequences of Obstruction?

Answer 21

Dilation (as previously discussed)

Stasis allows bacteria to replicate causing infection (UTI)

Stasis allows sediments to form - which can cause calculous (stone) formation

• Stones cause more obstruction which causes cycle of shite

Question 22

What is the main cause of obstruction (and thus UTIs) in children?

Answer 22

vesicoureteric reflux

Ureters enter bladder at a decreased angle - so they dont close properly

Causes hydroureter etc

Question 23

What are common causes of obstruction in adults?

Answer 23

In men:

• Benign Prostatic Hyperplasia (not a tumour) of prostate

In women:

• Uterine prolapse

Both sexes:

• Tumours
• Calculi

Question 24

What predisposes women to Urinary tract infections?

Answer 24

Short urethra _{compared to males}

Lack of prostatic bacteriostatic secretion

Closeness of urethral orifice to rectum

Sexual activity

Pregnancy – pressure on ureters and bladder

Question 25

Why is it that people with diabetes are predisposed to urinary tract infections?

Answer 25

Glucose in urine

Poor function of WBCs

Question 26

What are the acute and chronic complications of UTIs?

Answer 26

Acute:

• Severe sepsis & septic shock

Chronic:

• Chronic damage/infection can cause chronic pyelonephritis
  
  • This in turn leads to hypertension and chronic renal failure
• Calculi/obstructions can cause proximal dilation which can lead to chronic renal failure