UTI

Urinary tract anatomy

Two kidneys, two ureters, one bladder, and one urethra

Kidney function

Filters waste and excess fluid from blood and produces urine

Ureter function

Transports urine from kidneys to bladder

Bladder function

Stores urine temporarily before excretion

Urethra function

Carries urine from bladder to outside the body

Lower urinary tract infection

Infection involving the bladder or urethra

Upper urinary tract infection

Infection involving the kidneys or ureters

Cystitis

Inflammation of the bladder

Pyelonephritis

Bacterial infection causing inflammation of the kidney

Urethritis

Inflammation of the urethra

Prostatitis

Inflammation or infection of the prostate

Reason UTIs are more common in women

Shorter urethra decreases distance bacteria must travel to bladder

Ascending route of UTI infection

Bacteria from rectal flora enter urethra and ascend to bladder

Descending route of UTI infection

Hematogenous spread from bloodstream to kidneys

Lymphatic spread of UTI

Rare spread from adjacent organs via lymphatics

Bacteriuria

Presence of bacteria in urine

Pyuria

Presence of white blood cells in urine

Asymptomatic bacteriuria

Significant bacteriuria without clinical symptoms

Acceptable urine specimen collection method

Clean-catch midstream urine

Straight catheter specimen

Invasive urine collection using catheter

Indwelling catheter specimen

Urine collected from Foley catheter

Suprapubic aspiration

Direct needle aspiration of bladder, most invasive method

Purpose of boric acid tubes

Prevent bacterial overgrowth and preserve urine specimen

Importance of urine transport time

Delay allows bacterial multiplication and false results

Urine Gram stain purpose

Detect bacteria, WBCs, fungi, and contamination

Urine sterility principle

Urine should contain no normal flora

Urine Gram stain reporting

Semi-quantitative reporting of WBCs and bacteria

Nitrite screening test

Detects nitrate reduction by gram-negative bacteria

Leukocyte esterase test

Detects WBC activity indicating pyuria

Catalase screening

Rapid indicator of bacterial metabolism

Urine culture incubation temperature

35 to 37 degrees Celsius

Blood agar incubation atmosphere

CO2 at 37 degrees Celsius

MacConkey agar incubation

Ambient air at 37 degrees Celsius

Urine culture incubation time

Read at 10 hours and again at 24 hours

Significant bacteriuria threshold

Greater than 100,000 CFU per mL

Intermediate colony count

10,000 to 100,000 CFU per mL

Low colony count

Less than 10,000 CFU per mL

Pyelonephritis colony count

Typically greater than 100,000 CFU per mL

Cystitis colony count

Usually 10,000 to 100,000 CFU per mL

Vesiculocolonic fistula

Abnormal connection between bladder and colon

Asymptomatic bacteriuria colony count

High bacterial count without symptoms

Common community UTI pathogen

Escherichia coli (UPEC)

Second most common UTI pathogen

Staphylococcus saprophyticus

Gram-negative UTI pathogens

E

coli, Proteus, Klebsiella, Enterobacteriaceae

Gram-positive UTI pathogens

Staphylococcus saprophyticus, Enterococcus species

Staphylococcus aureus in UTI

Associated with hematogenous spread

Urogenital contaminating flora

Lactobacillus, Gardnerella vaginalis, mixed flora

Yeast in urine

Candida species, especially in hospitalized patients

Risk factor for UTI

Female sex due to shorter urethra

Pregnancy UTI risk

Hormonal changes and urinary stasis

Postmenopausal UTI risk

Decreased estrogen reduces Lactobacilli

Sexual activity risk factor

Introduces bacteria into urethra

Prostate enlargement risk

Urinary retention promotes infection

Best method to prevent overgrowth in urine

Boric acid preservative or refrigeration

Consequence of uncontrolled growth

False elevation of colony counts

Purpose of semi-quantitative urine plating

Differentiate contamination from true infection

Calibrated loop volume

10 microliters used for urine plating

Uncomplicated UTI

Responds readily to standard antibiotics

Complicated UTI

Associated with risk factors and harder to treat

Common hospital-acquired UTI pathogens

E

coli, Klebsiella, Proteus, Pseudomonas aeruginosa, Enterococcus, Candida

Recurrent UTI definition

Three or more UTIs per year

Recurrent UTI risk in women

Increases after each infection

Prevention of recurrent UTIs

Hydration, proper hygiene, post-intercourse voiding