Urinary Tract Infection

Question 1

What is a urinary tract infection (UTI)?

Answer 1

The presence of microorganisms in the urinary tract in symptomatic patients.

• typically caused by bacteria from gut flora
• bacteria usually enter through the urethra and ascend upwards

Question 2

What is involved in an upper UTI?

Answer 2

• pyelonephritis (kidney)
• ureteritis

Question 3

What is involved in a lower UTI?

Answer 3

• cystitis (bladder)
• urethritis
• prostatitis

Question 4

How are UTI’s classified?

Answer 4

1. Asymptomatic bateriuria
2. Acute cystitis
3. Complicated UTI
4. Recurrent (relapse, reinfection)

(2+3 guide choice and duration of abx)

Question 5

What is asymptomatic bacteriuria (ABU)?

Answer 5

The presence of a significant amount of bacteria in the urine of an asymptomatic individual

Does not require treatment in most patients except:
- pregnant females
- those who will undergo urological procedures with mucosal trauma

Question 6

What is acute (uncomplicated) cystitis?

Answer 6

The infection and S&S are localized to the bladder.
- Typically occurs in otherwise healthy, immunocompetent individuals with normal kidney and urinary tract system structure and function.

Caused by microorganisms ‘typical’ for UTI

Question 7

What are the typical microorganisms ‘typical’ for UTI?

Answer 7

E. Coli or Staphylococcus saprophyticus

Question 8

What is a complicated UTI?

Answer 8

The infection extends above the bladder or systemic illness (symptoms) are present.

Often factors exist that compromise the urinary tract (an anatomic or functional abnormality that affect urine flow) or host defences (immune-compromise)

Question 9

What is considered a ‘recurrent’ UTI and what can it be d/t?

Answer 9

> 3 UTIs in 1 year is considered frequent.

Reinfection: Occurs > 2 weeks after completion of antimicrobial therapy for a previous UTI

A new infection originating from outside of the urinary tract (even if the etiologic agent is the same)

Relapse: Occurs within 2 weeks of completing antimicrobial therapy.
Caused by the persistence of the same microorganism in the urinary tract (may suggest an antibiotic-resistant pathogen).

Question 10

What are uropathogenic bacteria?

Answer 10

• Bacteria that cause UTI’s
• virulence factors assist bacteria in avoiding host defences and enable infection of the urinary tract
• e.g. fimbriae bind to uroepithelial cells and flagella move bacteria ‘upstream’
  >80% of UTI’s in healthy individuals caused by uropathogenic E. Coli (UPEC)

Question 11

Bacteria that typically cause lower UTI’s are gram…?

Answer 11

gram-negative bacteria of the GI tract (called enterobacterales). E.g. escherichia coli, Klebsiella pneumoniae and proteus mirabilis

Question 12

The second most common cause of uncomplicated UIT is?

Answer 12

Staphylococcus saprophyticus = gram-positive bacteria from the GI tract that accounts for 42% of UTIs in sexually active females between the ages of 16-25.

Question 13

What are host defences against UTI?

Answer 13

1. Urine flow (unidirectional)
2. acidic pH of urine
3. complete and frequent bladder emptying
4. periurethral (female) and urethral (male) mucus-secreting glands (mucus traps ascending bacteria)
5. antibacterial secretions from urinary tract epithelial cells (released in response to the detection of uropathogens and prostate
6. uromodulin (produced by kidney tubule cells, released in the urine, and thought to block E. coli from binding to receptors on the uroepithelial surface)
7. immune defences (e.g. innate immune cells of the urinary tract
8. Normal urogenital flora (Lactobacillus species) in females defend against colonization.

Question 14

What role does estrogen play in a females defences against UTI?

Answer 14

• estrogen stimulates the secretion of glycogen-rich vaginal fluids
• Lactobacilli produce lactic aced from glycogen creating an acidic environment
• reduced pH and other antibacterial substances from lactobacilli inhibit colonization by other bacteria

Question 15

Why would bacteria that convert urea to ammonia (e.g. P. mirabilis, S. saprophyticus, S. aureas) be uropathogenic?

Answer 15

Urease producing bacteria make the urine more alkaline (virulence factor for uropathogenicity).

This also favours the formation of struvite stones

Question 16

Describe the pathogeneiss of a lower UTI.

Answer 16

1) Uropathogenic bacteria usually from the GI tract (or vagina) contaminate the periurethral area

2) Enter and colonize the urethra and migrate to the bladder.

3) E. coli attach to the surface of urpoepithelial cells (helps resist being flushed away)

4) Invade epithelial cells and replicate intracellularly (protected from elimination in the urine)

5) Epithelial cells and resident immune cells release cytokines and chemokines that recruit neutrophils (have a prominent role in bacterial clearance)

6) Bacteria and activated neutrophils release toxins that cause cell injury and inflammation (cystitis)

7) Death of infected cells leads to their eventual exfoliation and clearance

NOTE: some bacteria escape dying cells and invade surrounding cells (may enter a quiescent phase and become reactivated later)

Question 17

Why is female biological sex a risk factor for UTI?

Answer 17

1. female biological sex
   - 50-60% of females will have 1 UTI in their lifetime
   - shorter urethra length (distance to the bladder)
   - proximity of urethra to the anal and vaginal openings
   - decreased mucus production and urogenital flora post-menopause

Question 18

Why is recent sexual activity a risk factor for UTI?

Answer 18

• bacteria are pushed forward toward the urethra
• use of a diaphragm (may push against the urethra causing obstruction)
• use of spermicides (may alter vaginal pH and urogenital flora)
• increase risk with anal intercourse

Question 19

What is a common behavioural risk for (r/t to hygiene) that is a risk factor for UTI?

Answer 19

• wiping back to front

Question 20

How is family history a risk factor for UTI?

Answer 20

Genetic predisposition = increased expression of receptors for E. coli on epithelial cells

Question 21

How is impaired urine flow a risk factor for UTI?

Answer 21

• bacteria are not flushed out = encourages bacterial growth
• increases chance of infection spreading upwards

Question 22

What are possible causes of impaired urine flow?

Answer 22

• renal or urinary stones
• pregnancy
• tumour
• endometriosis (external compression)
• prostate enlargement
• urinary retention caused by neurological disease (neurogenic bladder)
• oliguria (e.g. dehydration)

Question 23

What are examples of medical instrumentation that are risk factors for UTI?

Answer 23

• indwelling catheter
• surgical procedures

Question 24

How is diabetes mellitus a risk factor for UTI?

Answer 24

Bacteria like glucose; diabetic neuropathy that impairs bladder emptying; immune compromise

Question 25

Why are older adults at risk for UTI?

Answer 25

- Poor bladder emptying - Weakened immune function - Reduced fluid intake - Postmenopausal changes (microbiome, mucus) - prostate hyperplasia in males - bowel incontinence

Question 26

What is acute cystitis?

Answer 26

- bladder wall is inflamed and possibly ulcerated - bladder wall irritation makes it oversensitive to filling - edema stimulates stretch receptors to initiate a sensation of bladder fullness with small urine volumes

Question 27

What are manifestations of cystitis?

Answer 27

- dysuria (inflammation causes pain when the bladder contracts) - urinary frequency and urgency (increased baldder wall sensitivity) - suprapubic pain, discomfort, tenderness - hematuria (ulcerations in severe cases) - cloudy, foul-smelling urine Note: systemic symptoms (e.g. fever, rigors, vomiting) typically absent with acute uncomplicated cystitis

Question 27

What are the differential diagnosis for cystitis?

Answer 27

- interstitial cystitis (negative urine culture, diagnosis of exclusion) - urethritis d/t gonorrhea or chlamydia (purulent discharge) - prostitis (older male, painful ejaculation) - atrophic vaginitis (postmenopausal recurrent dysuria)

Question 28

How do you diagnose cystitis?

Answer 28

1. urine dipstick (good for ruling out a UTI) - leukocyte esterase (purple) tests for WBCs in urine - nitrites (pink) test for gram-negative bacteria in the urine (conversion of nitrates to nitrites requires 4 hours) 2. Urine microscopy - identifies presence of WBCs (pyuria), RBCs (hematuria) and bacteria 3. urine culture - identifies the pathogen, counts bacteria, assesses antibiotic sensitivity BC guidelines - these tests are not necessary for an uncomplicated UTI presenting with typical symptoms

Question 28

What are some non-pharmacological recommendations for prevention of UTI?

Answer 28

- drink adequate fluids (1.5L/day) - empty the bladder frequently (when feel urge, every 2-3 hours, before bedtime, after sexual intercourse) - proper hygiene (wipe front to back) - avoid the use of diaphragms and vaginal spermicides - avoid urethral irritants such as bubble baths, bath products, and feminine hygiene products - wear lose fitting, breathable underwear (prevent moisture buildup) - cranberry products (juice or supplements) may help prevent recurrent UTIs. Contain a substance (proanthocyanidins) that decreases bacterial adherence to the bladder epithelium

Question 29

What are some pharmacological recommendations for prevention of UTI?

Answer 29

- vaginal suppositories containing lactobacilli - probiotics containing lactobacilli - vaginal estrogen creams for postmenopausal women

Question 30

What is polynephritis?

Answer 30

Inflammation of the kidneys caused by infection. - almost always bacterial - one or both kidneys might be involved - if extensive and bilateral, may progress to renal failure - classified as acute or chronic

Question 31

What are the routes of infection for polynephritis?

Answer 31

1. ascending - 90% of cases are associated with a lower UTI - bacteria move upwards via the ureter(s) 2. hematogenous - bacteria in teh blood (sepsis, infection elsewhere)

Question 32

What are risk factors for a lower UTI ascending and becoming a complicated UTI?

Answer 32

- anatomical abnormalities - urinary tract obstruction - pregnancy - Immune compromised states - Catheter associated UTI - Diabetes - Untreated cystitis

Question 33

What is acute polynephritis?

Answer 33

- affects the renal pelvis, tubules, and interstitial tissue - infection causes interstitial inflammation - neutrophils and pus enter into tubules - glomeruli are rarely affected - abscesses may form if infection severe

Question 34

What are the clinical manifestations of acute polynephritis?

Answer 34

- flank pain: lower back' described as dull and aching on one or both sides (d/t stretching of the renal capsule) - costovertebral angle tenderness (12th rib and lumbar spine) - systemic symptoms (fever, chills, nausea, vomiting) - and lower UTI symptoms

Question 35

What is chronic polynephritis?

Answer 35

- involves a recurrent or persistent UTI - an underlying structural (vesicoureteral reflux, chronic obstruction) or functional (neurogenic bladder) urological problem typically exists - accumulation of damage with each infection - functional tissue is progressively replaced by scar tissue - may lead to HTN or chronic renal insufficiency

Question 36

What is vesicoureteral reflux?

Answer 36

An abnormal structrual opening of the ureter into the bladder (ureterovesical junction) causing the reflux of urine. A flap normally (ureterovesical valve) normally forms at the junction of the ureter and bladder. Bladder contraction and increased bladder pressure compress the flap preventing reflux A congenital defect in theureterovesical junction (e.g. a short intravesical ureter) - bladder contraction during urination forces urine upwards into the ureter Usually suspected in children with recurrent pyelonephritis (most common urologic disease in children)

Question 37

What is the progression of chronic pyelonephritis?

Answer 37

- history of recurrent UTI and acute pyelonephritis - rapid treatment of acute infections is essential to prevent permanent damage and slow progression - may progress to renal failure over decades - affected kidney atrophies d/t scarring