Urinary tract infections (UTIs) are infections of the bladder, urethra, ureters, or kidneys that are most commonly caused by bacteria, especially E. coli. Infections of the bladder or urethra are called lower UTIs, whereas infections involving the kidneys or ureters are called upper UTIs. Because women have a shorter urethra and anal and genital regions that are closer in proximity, they are at higher risk of contracting UTIs than men. Other risk factors include sexual intercourse, indwelling urinary catheters, pregnancy, and abnormalities of the urinary tract. UTIs in otherwise healthy, nonpregnant, premenopausal women are considered uncomplicated. UTIs in men or individuals with other risk factors for treatment failure or serious outcomes, such as functional or anatomical abnormalities of the urinary tract, are considered complicated. Clinical findings depend on which part of the urinary tract is affected. Lower UTIs manifest with dysuria, suprapubic pain, urinary urgency, and increased urinary frequency, whereas upper UTIs additionally cause fever and flank pain. Diagnosis is usually clinical and can be supported with findings of pyuria and bacteriuria on urinalysis. A urine culture may be required for patients with a complicated lower UTI or equivocal urinalysis findings. Imaging is rarely required but may be indicated to rule out underlying factors (e.g., urinary tract obstruction, anatomical abnormalities). First-line empiric antibiotic therapy options for uncomplicated lower UTIs include oral nitrofurantoin, trimethoprim/sulfamethoxazole, or fosfomycin for up to 7 days. For complicated lower UTIs, broad-spectrum antibiotic therapy should be given for 7–14 days and treatable underlying factors should be addressed. Recurrent UTIs are common in women and antibiotic prophylaxis may be indicated. Catheter-associated urinary tract infections (CAUTIs) are among the most common healthcare-associated infections; they are frequently caused by resistant bacteria and are treated with catheter removal or replacement in addition to antibiotic therapy. Pregnant women should be screened and treated both for UTIs and for asymptomatic bacteriuria. For the management of upper UTIs, see “Pyelonephritis.”
- Infection ascends from the urethra to the bladder.
- Can ascend further to the ureters and the renal pelvises (see “ ”)
- Causative organisms
- : leading cause of UTI (approx. 80%) 
- Staphylococcus saprophyticus: 2nd leading cause of UTI in sexually active women
- Klebsiella pneumoniae: 3rd leading cause of UTI
- Proteus mirabilis
- Nosocomial bacteria: Serratia marcescens, Enterococci spp., and Pseudomonas aeruginosa are associated with increased drug resistance.
- Enterobacter species
- Ureaplasma urealyticum
- Immunocompromised patients and children are particularly susceptible to viral UTIs. 
- Adenovirus, cytomegalovirus, and BK virus are commonly involved in hemorrhagic cystitis. 
- Yeast: rare (usually Candida species) 
- Disseminated fungal infections (e.g., Blastomyces dermatitidis, Cryptococcus neoformans)
- Structural or functional abnormalities of the urinary tract ; 
- Pregnancy: hormonal changes during pregnancy → urinary stasis and vesicoureteral reflux → increased risk of UTIs
- Postmenopause: ↓ estrogen → ↓ vaginal lactobacilli → ↑ vaginal pH → ↑ colonization by E. coli 
- Chronic constipation: common cause of UTIs in children
- Prior conditions
- Sexual intercourse
Catheter-associated urinary tract infection (CAUTI)
- Caused by indwelling urinary catheters
- Most common cause of
Urinary tract infections are classified and treated based on location, severity, source of infection, and frequency. The presence of symptoms distinguishes UTI from asymptomatic bacteriuria, which only requires treatment in a select subset of patients.
|Classification of urinary tract infections |
|By clinical presentation ||Asymptomatic bacteriuria (ASB)|| |
|Urinary tract infection (UTI)|| |
|By location ||Lower UTI|
|By severity ||Uncomplicated UTI|
|Complicated UTI (cUTI)|| |
|By source of infection ||Community-acquired UTI|| |
|By frequency ||Recurrent UTI|| |
- Clinical features of lower UTI 
- Clinical features of upper UTI (pyelonephritis) 
- Additional features (special patient groups) 
Uncomplicated lower UTI in women
- Typical symptoms : Treatment may be initiated without further diagnostics.
- Atypical or unclear symptoms: Perform urinalysis using a urine dipstick test and/or microscopy.
- Complicated lower UTI in women
- Lower UTI in men
- Upper UTI: See “Diagnostics” in “Pyelonephritis.”
UTI is primarily a clinical diagnosis that is supported by typical findings on urinalysis. Urine culture is indicated in select cases to determine the causative pathogen and adapt antibiotic treatment.
Investigate isolated cystitis) for causes other than lower UTI (e.g., , ). (i.e., without concomitant
Laboratory studies 
- Indications: best initial test for all patients
- Procedure: visual, chemical (dipstick), and microscopic examination of urine
- Specimen collection method
Typical urinalysis findings of UTI 
- Pyuria: presence of white blood cells (WBCs) in the urine
- Bacteriuria: presence of bacteria in the urine 
- Leukocyte casts may indicate pyelonephritis.
- Micro- or macroscopic hematuria may be present.
- Alkaline urine (pH > 8); and struvite crystals in sediment: indicate (e.g., Proteus, Klebsiella, Staphylococcus saprophyticus) 
- The presence of squamous epithelial cells can be a sign of contamination.
Urine culture 
- Suspicion for complicated UTI or healthcare-associated UTI
- Suspicion for pyelonephritis or urosepsis
- Suspicion for uncomplicated cystitis with either of the following:
- Follow-up cultures for test of cure in the following cases:
- Typical colony findings
In patients with complicated or recurrent urinary tract infections, a urine culture should be obtained prior to initiating antibiotic treatment. False negative results are possible if a culture is obtained after the patient has received antibiotics.
In patients with lower abdominal pain and , consider bladder or ureteral irritation from an intraabdominal or pelvic infection unrelated to the urinary tract (e.g., appendicitis, diverticulitis). 
Additional diagnostics 
- Pregnancy test: indicated in women of childbearing age
- Testing for sexually transmitted infections (STIs)
- Not routinely performed in patients with lower UTI
- May be indicated to assess concomitant conditions (e.g., diabetes mellitus) and exclude differential diagnoses
Imaging is generally not indicated or helpful for the diagnosis of lower UTI, but it may be performed in select patients to rule out complicating factors (e.g., urinary tract obstruction) or if complicated pyelonephritis or urosepsis are suspected. For imaging indications and findings in upper UTI, see “Diagnostics” in “Pyelonephritis.”
- Indications may include:
- CT abdomen and pelvis with or without IV contrast
- Ultrasound of the kidneys and bladder
- Additional modalities include MRI abdomen and pelvis, voiding cystourethrography, and retrograde cystography.
Imaging is not routinely necessary for patients with uncomplicated lower UTI.
Interstitial cystitis (painful bladder syndrome) 
- Description: chronic, noninfectious cystitis of unknown etiology associated with recurring suprapubic pain
- Uncommon condition (0.6– 2% of women in the US) 
- Sex: ♀ > ♂
- Peak age: ≥ 40 years
- Associated with history of previous UTIs and/or diagnosis of other pain syndromes (e.g., fibromyalgia, irritable bowel syndrome)
- Individuals diagnosed with this condition are more likely to suffer from depression and anxiety disorders. 
- Symptoms have a gradual onset and last ≥ 6 weeks (required for diagnosis).
- Pain relieved by voiding and worsened by bladder filling (most common feature)
- Suprapubic pain, pressure, or discomfort 
- Increased urinary urgency and frequency
- Other exacerbating factors: sexual intercourse, exercise, alcohol use, and prolonged sitting
Diagnosis: Interstitial cystitis is generally a clinical diagnosis.
- Medical history to rule out other diagnoses
- Physical examination: anterior vaginal wall and bladder base tenderness on bimanual pelvic exam
- Urinalysis with microscopy and urine culture to rule out bacterial cystitis
- Other tests: indicated only in individuals with complex presentation 
- Behavioral modification (first-line): indicated for all diagnosed individuals 
- Multimodal pain management
- Invasive procedures: used as a last resort
Asymptomatic bacteriuria (ASB) 
- Presence of ≥ 100,000 CFU/mL in at least two voided urine samples in patients with no symptoms of UTI (e.g., dysuria, frequency, urgency, suprapubic pain)
- Bacteriuria typically resolves spontaneously in healthy, nonpregnant women without any side effects.
- Women with asymptomatic bacteriuria may progress to symptomatic UTI in the future more often than women with no bacteriuria.
- Etiology: E. coli is the most common causative organism.
- Risk factors
- Diagnosis: urinalysis with microscopy
- Treatment is recommended in:
- Individuals undergoing endourological procedures with possible mucosal trauma 
- Pregnant women: See “Treatment of ASB and lower UTIs in pregnant women” below.
- Treatment is not recommended in:
- Treatment is recommended in:
Other differential diagnoses
- Urethritis with sexually transmitted infections (e.g., Neisseria gonorrhoeae, Chlamydia trachomatis), Candida, or irritants
- Tuberculous cystitis (see “ ”)
- Drug-induced cystitis (e.g., cyclophosphamide, NSAIDs) or radiation-induced cystitis
- Hemorrhagic cystitis
- Structural abnormalities of the urethra (e.g., diverticula, strictures)
- Other diseases of the bladder (e.g., urolithiasis, bladder cancer, foreign objects)
The differential diagnoses listed here are not exhaustive.
General principles 
Antibiotic treatment is recommended for all patients with symptomatic UTI.
- The optimal therapy depends on disease severity, local resistance patterns, and patient characteristics (e.g., allergies).
- Initial treatment is with an empiric regimen, which is maintained for uncomplicated cystitis.
- In unclear or complicated cases, the regimen may subsequently have to be adjusted based on urine culture data.
- Consider the need for supportive treatment.
- For the treatment of upper UTI, see “Treatment of pyelonephritis.”
Uncomplicated lower UTI 
- Management can typically be done in the outpatient setting with oral therapy.
- Treatment duration depends on the chosen antibiotic agent.
- Symptom relief can be expected to occur after an average of 36 hours. 
- Persistent symptoms despite antibiotic therapy suggest complicated UTI and/or indicate the need to change the empiric therapy.
Empiric antibiotic treatment of uncomplicated lower UTIs
- First-line treatment
- Second-line treatment: beta-lactam antibiotics for 5–7 days
- Alternatives: Consider fluoroquinolones, e.g., ciprofloxacin for 3 days for patients with previous infections with bacteria resistant to other drug classes. 
Complicated lower UTI 
- There are few recommendations for the empiric antibiotic treatment of complicated lower UTI.
- In addition to antibiotic therapy, complicating factors (e.g., obstruction) should be treated, if possible.
- For UTI in men, referral to urology may be warranted especially in the following cases:
- Hospitalization and initial intravenous treatment may be necessary in the following cases: 
Antibiotic treatment of complicated lower UTIs 
- Antibiotic therapy must be adapted to culture results and is commonly given for 7–14 days.
- Options for the initial empiric treatment of complicated lower UTIs include:
- Fluoroquinolones PO or IV: e.g., ciprofloxacin or levofloxacin
- Beta lactams
- Aminoglycosides (e.g., gentamicin ): treatment option if fluoroquinolones or beta lactams are contraindicated or as an addition to beta lactams
- Reasonable options if the pathogen is susceptible include: 
Management of complicating factors
- Nephrolithiasis: In UTI with renal obstruction, urgent urology consultation is required for drainage. 
Indwelling medical devices (e.g., ureteral stents, percutaneous nephrostomy tubes) 
- Management of infections may require exchange or removal of the device, especially when it is obstructed.
- Urology should be consulted urgently for further management.
- Other treatable factors should be addressed: e.g., optimal blood sugar control for diabetics.
Recurrent UTI 
Choice of antibiotic
- First recurrence: See “Antibiotic treatment for uncomplicated lower UTIs” and “Antibiotic treatment for complicated lower UTIs” for initial empiric regimens.
- Frequent recurrences
- Regimens should be tailored to the patient and prior culture results.
- Consider increased antibiotic resistance to standard agents.
- Antibiotics must be adapted to the current culture results once available.
- May be considered for motivated women who have documented recurrent UTIs.
- Patients are given a prescription to fill when symptoms start.
- Reevaluation is required if no improvement occurs within 48 hours.
- Follow-up: Consider test of cure with repeat urine culture only if symptoms persist beyond 7 days.
- Indication: may be considered in all women with recurrent uncomplicated UTIs
- Continuous prophylaxis
- Intermittent or postcoital prophylaxis
- There is insufficient high-quality data to support the use of cranberry products for preventing UTIs. 
- Topical estrogen therapy should be considered in postmenopausal women.
- Behavioral modifications (e.g., increased fluid intake, postcoital voiding) may be helpful.
- Candida isolated from the urine rarely indicates systemic infection, but it may be a marker for greater mortality in severely ill patients.
- Predisposing factors should be treated in all cases of candiduria, e.g., by removing indwelling catheters whenever possible.
- Indications for antifungal treatment include symptomatic cystitis or pyelonephritis, neutropenia, or a planned urologic procedure.
- Commonly used antifungals include fluconazole and amphotericin B.
- Consult the infectious disease service for assistance with appropriate antifungal treatment.
Behavioral modifications 
- Increased fluid intake
- Timely bladder voiding
- Postcoital voiding
- Adequate genital hygiene
- Clean intermittent catheterization
- Prophylaxis: indicated for recurrent urinary tract infections (see ”Chemoprophylaxis” in “Recurrent UTI” for details)
- Catheter-associated UTI (CAUTI): symptomatic UTI occurring in a patient with an indwelling urinary catheter OR within 48 hours after removal of a urinary catheter
- Catheter-associated asymptomatic bacteriuria (CAASB): bacteriuria (≥ 105CFU/mL) without symptoms in a patient with an indwelling urinary catheter OR within 48 hours after removal of a urinary catheter
- Epidemiology: CAUTIs are among the most common healthcare-associated infections. 
- Causative organisms are likely to have antibiotic resistance.
- In patients with long-term catheterization (≥ 30 days), UTIs are typically polymicrobial.
- Clinical features
- Indications: features consistent with potential infection
- Specimen collection: ideally from the sampling port of a newly inserted device using aseptic technique
- Diagnostic criteria
To reduce false-positive results, avoid sampling urine for culture from previously inserted catheters or collection bags, as these sites are frequently colonized by bacteria within a few hours of catheter insertion. 
Catheter removal or replacement
- Remove if no longer necessary.
- Replace if still necessary and present for > 2 weeks.
- Antibiotic therapy
- Prevention: See “Prevention of catheter-associated urinary tract infections.”
Special patient groups
UTI in older adults 
- UTI is very common in advanced age, both in individuals who live in long-term care facilities and those who do not.
- Symptoms of UTI are more commonly atypical (e.g., back pain, pelvic pain, constipation, urinary incontinence, and altered mental status).
- Management principles are generally the same as outlined above.
- Preventative strategies include increasing mobility and consumption of cranberry products.
UTI in pregnancy 
- Pregnancy may increase the risk of recurrent bacteriuria and UTIs.
- Factors involved
Asymptomatic bacteriuria in pregnancy 
- See “Asymptomatic bacteriuria” for diagnostic criteria.
- Screening is recommended for all pregnant women in the first trimester.
- Treatment is always required, as evidence suggests that it reduces the risk of pyelonephritis and fetal complications.
Treatment of ASB and lower UTIs in pregnancy 
Although UTI in pregnancy is generally considered complicated, treatment regimens for ASB and lower UTI in pregnancy may include those typically used for uncomplicated UTI and should be adapted to the patient's individual risk and urine culture results. 
- Upper UTIs generally require hospitalization and intravenous treatment; see “Pyelonephritis in pregnancy.”
- Empiric antibiotics for ASB and lower UTI considered appropriate during pregnancy include:
- Antibiotics that are potentially appropriate during specific stages of pregnancy include:
- Antibiotics that should be avoided include fluoroquinolones and aminoglycosides.
- Follow-up culture should be considered a week after treatment for ASB and UTI.
UTI in children and adolescents 
- UTIs are common in children.
- Approx. 8% of girls and 2% of boys will have had a UTI by the age of 7 years.
- Female sex
- Uncircumcised infants
- Urogenital anomalies (e.g., vesicourethral reflux, urinary obstruction)
- Functional anomalies (e.g., chronic constipation, withholding behavior)
Urinalysis and urine culture are indicated in patients with suspected UTI that fulfill one of the following criteria:
- Any febrile infant or child with an abnormal urinary tract or family history of urinary tract disease
- Circumcised boys < 12 months of age with: fever or no obvious cause of infection
- Female and uncircumcised male children 2–24 months of age with a history of previous UTI, fever of unknown source or duration > 24 hours, ill appearance, or suprapubic tenderness
- Children > 24 months with a suspected UTI based on urinary symptoms (see “Clinical features” above)
- Criteria for diagnosis include both a positive urinalysis (pyuria and/or bacteriuria) and urine culture (> 50,000 CFU/mL in a specimen obtained from transurethral catheterization or suprapubic aspiration).
Renal and bladder ultrasound indicated in:
- Children 2–24 months of age with a febrile UTI
- Children with treatment failure, abnormal voiding, abdominal mass, recurrent UTI, or poor likelihood of follow-up
- Voiding cystourethrography (VCUG) is used in:
- Treatment principles in children are similar to those in adults.
- Empiric therapy: Reasonable first-line options include : 
- Antibiotics can be adjusted after culture and susceptibility results have been obtained.
- When associated with structural abnormalities, additional management of the underlying condition may be required.
Oral and parenteral antibiotics are equally effective. Hospitalization should be considered in severely ill children and those unable to tolerate oral intake.