Urinary Tract Infection Flashcards
What is a urinary tract infection (UTI)?
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
What is involved in an upper UTI?
- pyelonephritis (kidney)
- ureteritis
What is involved in a lower UTI?
- cystitis (bladder)
- urethritis
- prostatitis
How are UTI’s classified?
- Asymptomatic bateriuria
- Acute cystitis
- Complicated UTI
- Recurrent (relapse, reinfection)
(2+3 guide choice and duration of abx)
What is asymptomatic bacteriuria (ABU)?
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
What is acute (uncomplicated) cystitis?
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
What are the typical microorganisms ‘typical’ for UTI?
E. Coli or Staphylococcus saprophyticus
What is a complicated UTI?
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)
What is considered a ‘recurrent’ UTI and what can it be d/t?
> 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).
What are uropathogenic bacteria?
- 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)
Bacteria that typically cause lower UTI’s are gram…?
gram-negative bacteria of the GI tract (called enterobacterales). E.g. escherichia coli, Klebsiella pneumoniae and proteus mirabilis
The second most common cause of uncomplicated UIT is?
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.
What are host defences against UTI?
- Urine flow (unidirectional)
- acidic pH of urine
- complete and frequent bladder emptying
- periurethral (female) and urethral (male) mucus-secreting glands (mucus traps ascending bacteria)
- antibacterial secretions from urinary tract epithelial cells (released in response to the detection of uropathogens and prostate
- uromodulin (produced by kidney tubule cells, released in the urine, and thought to block E. coli from binding to receptors on the uroepithelial surface)
- immune defences (e.g. innate immune cells of the urinary tract
- Normal urogenital flora (Lactobacillus species) in females defend against colonization.
What role does estrogen play in a females defences against UTI?
- 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
Why would bacteria that convert urea to ammonia (e.g. P. mirabilis, S. saprophyticus, S. aureas) be uropathogenic?
Urease producing bacteria make the urine more alkaline (virulence factor for uropathogenicity).
This also favours the formation of struvite stones
Describe the pathogeneiss of a lower UTI.
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)
Why is female biological sex a risk factor for UTI?
- 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
Why is recent sexual activity a risk factor for UTI?
- 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
What is a common behavioural risk for (r/t to hygiene) that is a risk factor for UTI?
- wiping back to front
How is family history a risk factor for UTI?
Genetic predisposition = increased expression of receptors for E. coli on epithelial cells
How is impaired urine flow a risk factor for UTI?
- bacteria are not flushed out = encourages bacterial growth
- increases chance of infection spreading upwards
What are possible causes of impaired urine flow?
- renal or urinary stones
- pregnancy
- tumour
- endometriosis (external compression)
- prostate enlargement
- urinary retention caused by neurological disease (neurogenic bladder)
- oliguria (e.g. dehydration)
What are examples of medical instrumentation that are risk factors for UTI?
- indwelling catheter
- surgical procedures
How is diabetes mellitus a risk factor for UTI?
Bacteria like glucose; diabetic neuropathy that impairs bladder emptying; immune compromise
Why are older adults at risk for UTI?
- Poor bladder emptying
- Weakened immune function
- Reduced fluid intake
- Postmenopausal changes (microbiome, mucus)
- prostate hyperplasia in males
- bowel incontinence
What is acute cystitis?
- 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
What are manifestations of cystitis?
- 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
What are the differential diagnosis for cystitis?
- 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)
How do you diagnose cystitis?
- 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) - Urine microscopy - identifies presence of WBCs (pyuria), RBCs (hematuria) and bacteria
- 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
What are some non-pharmacological recommendations for prevention of UTI?
- 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
What are some pharmacological recommendations for prevention of UTI?
- vaginal suppositories containing lactobacilli
- probiotics containing lactobacilli
- vaginal estrogen creams for postmenopausal women
What is polynephritis?
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
What are the routes of infection for polynephritis?
- ascending
- 90% of cases are associated with a lower UTI
- bacteria move upwards via the ureter(s) - hematogenous
- bacteria in teh blood (sepsis, infection elsewhere)
What are risk factors for a lower UTI ascending and becoming a complicated UTI?
- anatomical abnormalities
- urinary tract obstruction
- pregnancy
- Immune compromised states
- Catheter associated UTI
- Diabetes
- Untreated cystitis
What is acute polynephritis?
- 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
What are the clinical manifestations of acute polynephritis?
- 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
What is chronic polynephritis?
- 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
What is vesicoureteral reflux?
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)
What is the progression of chronic pyelonephritis?
- 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
