A urinary tract infection is invasion of the normally sterile urinary tract by microorganisms, most often gram-negative bowel flora that ascend through the urethra. Escherichia coli causes the majority of community infections; Klebsiella, Proteus, Enterococcus, and Pseudomonas are more common in hospital and catheter-related infections.

Classification used in current practice (IDSA 2025)

• Uncomplicated (cystitis) — infection limited to the bladder, in any sex, without systemic signs
• Complicated — infection beyond the bladder: pyelonephritis, fever or other systemic signs, catheter-associated infection with systemic signs, prostatitis, or urosepsis
• Asymptomatic bacteriuria (ASB) — bacteria in urine without urinary symptoms; not an infection that needs treatment in most clients

Risk factors

• Female anatomy (short urethra close to the anus); sexual activity; spermicide use
• Urinary obstruction or stasis — stones, enlarged prostate, neurogenic bladder, incomplete emptying
• Indwelling urinary catheter (the single largest risk factor for hospital UTI)
• Diabetes mellitus (glucosuria, impaired immunity, autonomic neuropathy), pregnancy, menopause (loss of estrogen changes vaginal flora), immunosuppression, older age

Host defenses include regular complete voiding, urine flow, normal vaginal flora, and the ureterovesical valve. Anything that stops urine flow or bypasses these defenses raises risk.

Lower tract (cystitis)

• Dysuria (burning), frequency, urgency, suprapubic pain or pressure
• Cloudy or foul-smelling urine, hematuria
• Usually no fever

Upper tract (pyelonephritis) — see Topic 52

• Fever, chills, flank pain, costovertebral angle (CVA) tenderness, nausea, vomiting

Atypical presentations — assess carefully

• Older adults: new or worsening confusion, falls, loss of appetite, or new incontinence may be the only signs; fever may be absent
• Diabetes: infection can be silent or atypical because of neuropathy and impaired immune response
• Spinal cord injury / neurogenic bladder: no dysuria; look for fever, increased spasticity, autonomic dysreflexia, cloudy urine, or change in continence

Sepsis warning signs: hypotension, tachycardia, tachypnea, altered mental status, fever or hypothermia, low urine output.

Urinalysis (dipstick and microscopy)

Nitrite plus leukocyte esterase positive together strongly suggest bacterial UTI.

Urine culture and sensitivity

• Collect before the first antibiotic dose
• Clean-catch midstream specimen: clean the urethral area front to back (women) or the glans with foreskin retracted (uncircumcised men), start voiding into the toilet, then collect the middle portion
• Catheterized client: aspirate from the sampling port with aseptic technique — never from the drainage bag
• Send promptly; if delayed, refrigerate per laboratory policy
• Young children not toilet-trained: a bag specimen is not acceptable for culture (high contamination); use catheterization or suprapubic aspiration per protocol
• A count of ≥ 100,000 CFU/mL of one organism is the classic threshold; lower counts can be significant in symptomatic clients (≥ 1,000 CFU/mL with symptoms in a catheterized client)

Other: blood cultures, CBC, lactate, and creatinine if sepsis is suspected; imaging (ultrasound or CT) for recurrent, complicated, or non-responding infection, or suspected obstruction.

Antibiotics — choice depends on local resistance, allergies, kidney function, pregnancy, and prior cultures.

• Duration of cystitis treatment: fosfomycin single dose; TMP-SMX 3 days; nitrofurantoin 5 days; beta-lactams 3–7 days; men usually 7 days
• Complicated UTI in a client who is improving: 5–7 days of a fluoroquinolone or 7 days of another effective agent (IDSA 2025); switch from IV to oral when stable; men with suspected acute bacterial prostatitis may need a longer course (often 10–14 days)
• Phenazopyridine (urinary analgesic): turns urine and body fluids orange-red (stains contact lenses and clothing); use no more than 2 days; it does not treat infection; avoid with kidney impairment and G6PD deficiency (hemolysis)

Asymptomatic bacteriuria — do not treat routinely. Treatment is indicated mainly in pregnancy and before urologic procedures that breach the mucosa. Clients with catheters, spinal cord injury, diabetes, and older adults are not treated for bacteriuria alone; instead, monitor for symptoms and systemic signs. Unnecessary treatment drives resistance and C. difficile.

Urosepsis is managed as sepsis: early recognition, cultures, antibiotics within 1 hour when septic shock is likely, IV crystalloid for hypotension or high lactate, and source control (relieve obstruction, remove or change catheter).

Listed in priority order.

1. Recognize and act on sepsis
   • Check vital signs, mental status, SpO₂, and urine output; report hypotension (systolic < 90 mmHg or MAP < 65 mmHg), tachycardia, and tachypnea at once
   • Airway and oxygenation are assessed first; give oxygen if SpO₂ is low
   • Establish IV access and start prescribed fluid resuscitation for hypotension; obtain blood and urine cultures, then give antibiotics without delay (do not hold antibiotics while waiting for results)
   • Measure lactate per protocol; monitor hourly output
2. Prevent catheter-associated UTI (CAUTI)
   • Insert only when indicated; remove as soon as possible; review need daily; use alternatives (bladder scanner, intermittent catheterization, external catheters)
   • Aseptic insertion with sterile equipment
   • Secure the catheter to prevent movement and urethral traction
   • Keep a closed drainage system; keep the bag below bladder level and off the floor; keep tubing free of kinks and dependent loops
   • Empty the bag regularly (before it is full) into a separate clean container for each client, without letting the spigot touch the container
   • Routine hygiene only — do not clean the meatus with antiseptics; do not change catheters or bags at fixed intervals (change for obstruction, infection, or a broken closed system)
3. Give antibiotics as scheduled and monitor for adverse effects and allergic reactions
4. Promote fluids (about 2–3 L/day unless restricted for heart or kidney disease) to dilute urine and flush bacteria
5. Comfort: warmth to suprapubic area or a warm sitz bath for bladder discomfort; analgesics as prescribed
6. Monitor high-risk clients (neurogenic bladder, diabetes, older adults) for fever, confusion, and change in vital signs

• Finish the full antibiotic course even when symptoms improve
• Drink enough fluid to keep urine pale; void every 3–4 hours and empty the bladder completely
• Void soon after sexual intercourse
• Wipe front to back; showers are preferred over long tub baths or bubble baths
• Avoid douches, feminine sprays, and scented products — they disrupt protective vaginal flora
• Avoid spermicide-coated contraceptives if UTIs recur
• Cranberry products may modestly reduce recurrence in women with recurrent UTI; they do not treat an active infection
• Postmenopausal women with recurrent UTI: vaginal estrogen may be offered by the provider
• Limit bladder irritants (caffeine, alcohol) while symptomatic
• Ciprofloxacin/levofloxacin: use sunscreen and protective clothing; separate from dairy and mineral supplements; stop and report tendon pain, numbness or tingling, or confusion
• Nitrofurantoin: take with food; report cough, shortness of breath, or numbness
• Return if fever, chills, flank pain, vomiting, or blood in urine develops, or if symptoms persist after 48–72 hours of treatment

• Urosepsis / septic shock — hypotension, tachycardia, confusion, low urine output, rising lactate
• Pyelonephritis — ascending infection; fever, flank pain, CVA tenderness
• Obstructed infected kidney (e.g., stone with fever) — urologic emergency requiring drainage
• Renal or perinephric abscess, chronic kidney damage with repeated upper-tract infection
• Prostatitis in men; recurrent infection from incomplete emptying
• C. difficile infection after antibiotics (frequent watery stools)

• E. coli is the most common cause; infections ascend from the urethra
• Cystitis = dysuria, frequency, urgency, suprapubic pain; pyelonephritis adds fever, flank pain, CVA tenderness
• Older adults: confusion may be the only sign; diabetes may cause silent infection
• Nitrite + leukocyte esterase positive strongly suggest bacterial UTI
• Clean-catch midstream specimen, before antibiotics; catheter specimen from the sampling port, never the bag; no bag specimens for culture in infants
• Asymptomatic bacteriuria is not treated except in pregnancy and before mucosal-breaching urologic procedures — monitor high-risk clients instead
• CAUTI prevention: remove early, secure the catheter, bag below bladder, closed system, no routine changes, no antiseptic meatal care
• Sepsis from UTI: IV access and fluids for hypotension, cultures, then antibiotics within 1 hour
• Fluoroquinolones: tendon rupture, neuropathy, photosensitivity; separate from calcium and antacids
• Phenazopyridine: orange urine, 2 days maximum, not an antibiotic
• Prevention: fluids, void after intercourse, front-to-back wiping, no douching, showers