Urinary Tract Infections Flashcards
urinary tract infections (UTIs) - overview
*UTIs are the most common infection encountered in the outpatient setting
*common problem in hospitalized patients, particularly those with urinary catheters
*clinical manifestations differ based on affected portion of urinary tract
*treatment regimen differs based on anatomic location of infection
bacteriuria - defined
*bacteria in the urine, > 10^5 organisms per milliliter
pyuria - defined
- > 10 WBCs per high power field
cystitis - defined
*inflammation of the bladder
complicated UTI - defined
*anatomic, functional, or pharmacologic factors that predispose the patient to persistent infection, recurrent infection, or treatment failure
CA-UTI - defined
*catheter-associated UTI
pyelonephritis - defined
*inflammation of the kidneys
prostatitis - defined
*inflammation of the prostate
pathogenesis of UTIs
*most commonly, bacteria cause infection by ascending the urinary system (95% of the time)
*in some cases, bacteria (esp. Staph aureus) can cause infection hematogenously (bloodstream infection causing a UTI; check blood cultures if S. aureus grows in urine)
bacterial factors contributing to the pathogenesis of UTIs: increased bacterial adherence to uroepithelial cells
*mediated via fimbria (aka pili)
*2 important types in E. coli:
-Type 1 fimbriae
-P fimbriae
E. coli bacterial factor: Type-1 Fimbriae
*mannose-sensitive
*adhere to mannosylated proteins on uroepithelial cells
*can be detached by exposure to mannose
*bacterial tropism for BLADDER (cystitis)
E. coli bacterial factor: P fimbriae
*mannose-resistant
*adhere to glycophospholipids embedded in outer surface of plasma membrane of uroepithelial cells
*tropism for upper urinary tract (PYELONEPHRITIS)
bacterial factors contributing to the pathogenesis of UTIs: resistance to serum cidal activity
*allows the bacteria to evade normal host defences
bacterial factors contributing to the pathogenesis of UTIs: hemolysin production
*hemolysin is a cell toxin
*important in pyelonephritis
bacterial factors contributing to the pathogenesis of UTIs: ability to synthesize essential amino acids
*guanine, arginine, and glutamine required for bacterial growth in urine
bacterial factors contributing to the pathogenesis of UTIs: urease production
*Proteus mirabilis
*important in pyelonephritis and urolithiasis
*associated with STRUVITE stones and staghorn calculi
bacterial factors contributing to the pathogenesis of UTIs: bacterial motility
*ascend against urine flow
bacterial factors contributing to the pathogenesis of UTIs: endotoxin production
*decreases ureteral peristalsis, allowing bacteria to ascend
host factors that prevent UTIs
*urine: inhibits bacterial growth
-high urea concentration
-low pH
*mechanical flow: flushes out urinary tract
*urethra (longer urethra is protective)
host factors contributing to the pathogenesis of UTIs: obstruction or reflux
*urethral stenosis
*posterior urethral valves
*kidney stones
*polycystic kidney disease
*spinal cord injury or neurogenic bladder
*prostatic hypertrophy
*pregnancy
host factors of WOMEN contributing to the pathogenesis of UTIs
*short urethra
*bacterial colonization of vagina and periurethral area
*sexual intercourse:
-facilitates movement of bacteria from anterior urethra to bladder
-trauma to urethra
-diaphragm use (can cause urethral trauma)
-spermacide use (inhibit lactobacillus)
host factors contributing to the pathogenesis of UTIs: bladder catheterization
*catheters bypass the urethra
*100% of patients will have bacteriuria within 3 days of catheter placement
host factors contributing to the pathogenesis of UTIs: susceptibility of renal medulla
*high ammonia concentrations inactivate complement
*high osmolality inhibits migration of neutrophils
pathogens that commonly cause community-acquired UTIs
*E. coli (gram NEGATIVE) is by far the leading cause
*followed by Klebsiella (esp. in people with hx of DM) and Proteus spp.
*Staph saprophyticus if young woman, sexually active, gram POSITIVE
pathogens that commonly cause hospital-acquired (nosocomial) UTIs
*E. coli is the leading cause
*followed by other gram-negative rods (Klebsiella, Proteus, enterococci)
*Pseudomonas and Candida (esp. with catheters)
*Staph epidermidis
asymptomatic bacteriuria (ASB) - overview
*bacteria in the urine with NO symptoms
*positive urine culture, > 10^5 cfu/mL
*it does NOT prove infection; it is just a number to state that the culture is unlikely due to contamination
*pyuria also is not predictive on its own
*it is the presence of SYMPTOMS + PYURIA + BACTERURIA that denotes infection
asymptomatic bacteriuria (ASB) - treatment in the elderly
*no benefit to treating ASB with antibiotics:
-no improvement in “mental status”
-no difference in the number of symptomatic UTIs
-no improvement in chronic urinary incontinence
-no improvement in survival
asymptomatic bacteriuria (ASB) - indications to treat
*screen and treat ASB in 2 scenarios:
1. pregnancy
2. patients undergoing urologic procedure in which bleeding is anticipated
*children not routinely screened, but if there, treat
*otherwise, DO NOT TREAT
sterile pyuria
*WBCs in urine, but no bacteria
*2 common causes:
1. urethritis, usually due to STIs (Chlamydia trachomatis or Neisseria gonorrhoeae)
2. GU tuberculosis
urethritis - clinical presentation
*primary symptom: burning on urination
*NO frequency or urgency
*urine culture colony counts lower
urethritis - common causes
*E. coli and other common UTI causes
*STIs: Chlamydia trachomatis and Neisseria gonorrhoeae (purulent discharge from the urethra)
*Ureaplasma urealyticum
*noninfectious (trauma, allergic, chemical)
cystitis (lower tract infection) - clinical presentation
*dysuria
*frequency
*urgency
*suprapubic pain
pyelonephritis (upper tract infection) - clinical presentation
*fever
*chills
*flank pain
*costovertebral angle tenderness
*nausea & vomiting
*hypotension
*tachycardia
*plus, symptoms of cystitis may be present
prostatitis - clinical presentation
*fevers, chills
*dysuria
*urinary frequency
*bladder outlet obstruction can occur
*PE: high fever, may appear septic, moderate tenderness of suprapubic region
*rectal exam: exquisitely tender and diffusely enlarged prostate
prostatitis - treatment
*ABX therapy should be prolonged (4-6 weeks) as most ABX do not penetrate well into acidic, lipophilic environment of prostate
*prostatic massage contraindicated
diagnosis of UTI
*symptoms plus pyuria on urine dipstick or urinalysis
*urine dipstick:
-positive LEUKOCYTE ESTERASE
-positive nitrites can be seen
*U/A required for evaluation of complicated UTI
*note - WBC casts can be seen in pyelonephritis
urine gram stain for UTIs
*should be performed in all pts with suspected pyelonephritis
* > 1 bacteria/hpf correlates with > 10^5 organisms/ml
*in combination with pyuria + symptoms = infection
urine culture for UTIs
*should be performed in all patients EXCEPT young, sexually active women with suspected (uncomplicated) cystitis
*urine in the bladder is normally sterile, but urethra and periurethral areas are very diffiuclty to sterilize, esp in woemn
*obtain quantitative culture of midstream clean-voided urine
indications for anatomic investigations in UTIs
*all upper tract disease (pyelonephritis)
*relapse or failure to improve after appropriate ABX therapy
*pre-pubertal females after their 2nd UTI
*UTI in males of any age
examples of anatomic investigations in UTIs
- ultrasound - first line test
- CT scan (to exclude dx of perinephric abscess in pts with pyelonephritis if no improvement after 48 hrs)
- intravenous pyelogram (after abnormal ultrasound)
treatment of uncomplicated cystitis
*short course therapy (3-5 days):
-nitrofurantoin = treatment of choice
-TMP-SMX
-ciprofloxacin
*beta lactams as an alternative (3-7 days)
do NOT use short-course therapy for UTIs in…
*males
*upper tract symptoms (pyelonephritis)
*recurrent or relapse of symptoms
*more than 7 days of symptoms
treatment of pyelonephritis
*all patients should have urine culture + susceptibility test performed
*adjust antibiotics based on results
*7-10 days of antibiotics:
-IV ceftriaxone
-oral if non-toxic and able to tolerate po (ciprofloxacin, TMP-SMX)
complications of pyelonephritis
*bacteremia
*septic shock
*perinephric abscess
*emphysematous pyelonephritis:
-aggressive form of pyelonephritis with necrosis, vascular compromise, gas production
-most commonly in people with poorly controlled DM
-urologic emergency
chronic (recurrent) pyelonephritis
*due to multiple episodes of acute pyelonephritis
*risk factors: VUR, stone disease
*tubular atrophy, corticomedullary scarring, blunted calyces
*“thyroidization” of the kidney:
-atrophic tubules with eosinophilic proteinaceous material resembling thyroid tissue on pathology
-waxy casts in urine
xanthogranulomatous pyelonephritis
*unusual variant of chronic pyelonephritis
*most cases occur in the setting of obstructive nephrolithiasis
*destruction of kidney due to granulomatous tissue containing lipid-laden macrophages
*can be confused with renal malignancy (looks like a tumor)
xanthogranulomatous pyelonephritis - CT findings
*“bear claw” appearance
*massive caliectasis
*parenchyma enlargement
*often associated with stone
prevention of urinary tract infections
*remove urinary catheters ASAP
*in and out straight catheterization preferable to indwelling catheterization in patients who are unable to void on their own
*long term antibiotic prophylaxis generally NOT effective
*ensure liberal fluid intake
*contraception change (avoid spermacide)
*post-coital prophylaxis can be considered in sexually active women
*intravaginal estrogen can be helpful in preventing cystitis in elderly women with atrophic vaginitis
*methenamine
