Clinical Subject Page
Urinary Tract Infection (UTI)
Urinary Tract Infection (UTI) is an infection involving any part of the urinary tract, including the urethra, bladder, ureters, or kidneys. Most UTIs are caused by bacteria and commonly affect the bladder
Also called
ICD-10
Specialty
Onset
Reviewed
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OverviewOverview
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Etiology & Risk FactorsEtiology & Risk Factors
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PathophysiologyPathophysiology
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Clinical PresentationClinical Presentation
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History TakingHistory Taking
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Physical ExaminationPhysical Examination
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InvestigationsInvestigations
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DiagnosisDiagnosis
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ManagementManagement
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ComplicationsComplications
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PrognosisPrognosis
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Key Points / Clinical PearlsKey Points / Clinical Pearls
Overview
-Urinary Tract Infection (UTI) can be classified as:
- Lower UTI: mainly affects the bladder and urethra
- Upper UTI: involves the kidneys, such as Pyelonephritis
–UTIs may also be classified as:
- Uncomplicated UTI: occurs in otherwise healthy individuals without significant urinary tract abnormalities
- Complicated UTI: associated with factors such as obstruction, stones, catheters, structural abnormalities, or significant comorbidities’
–Escherichia coli (E. coli) is the most common causative organism.
Etiology & Risk Factors
-Etiology
–Most UTIs result from ascending bacterial infection from the perineum into the urethra and bladder.
Common organisms include:
- Escherichia coli (E. coli)
- Klebsiella species
- Proteus species
- Enterococcus species
-Risk Factors
- Female sex
- Sexual activity
- Pregnancy
- Urinary obstruction
- Kidney stones
- Diabetes mellitus
- Urinary catheterization
- Structural urinary tract abnormalities+
Pathophysiology
Periurethral bacterial colonization → ascending bacterial infection → bladder colonization → mucosal inflammation → urinary symptoms → possible ascending infection → Pyelonephritis
Clinical Presentation
–Symptoms
- Dysuria
- Urinary frequency
- Urinary urgency
- Suprapubic discomfort
- Hematuria
- Cloudy or malodorous urine
-Signs:
- Suprapubic tenderness
- Fever in more significant infection
- Costovertebral angle tenderness if the kidneys are involved
History Taking
-Ask about:
- Dysuria
- Frequency and urgency
- Suprapubic pain
- Hematuria
- Fever and chills
- Flank or back pain
- Nausea and vomiting
- Previous UTIs
- Recurrent infections
- Pregnancy
- Sexual activity
- Kidney stones
- Urinary obstruction
- Catheter use
- Recent antibiotics
Physical Examination
-General Examination
- Temperature
- Heart rate
- Blood pressure
- Hydration status
- Signs of sepsis
-System-Specific Examination:
- Suprapubic tenderness
- Costovertebral angle tenderness
- Abdominal examination for obstruction or other pathology
Investigations
-Biochemistry / Specific Tests
- Urinalysis
- Urine culture and antimicrobial susceptibility testing when indicated
- Serum creatinine and eGFR in complicated infection, systemic illness, or suspected kidney dysfunction
- Serum electrolytes when clinically indicated
-Typical urinalysis findings include:
- Pyuria
- Positive leukocyte esterase
- Bacteriuria
- Possible hematuria
- Nitrites may be positive with nitrate-reducing organisms
-Imaging
Not routinely required for uncomplicated UTI.
Renal ultrasound or CT may be considered when there is:
- Suspected urinary obstruction
- Kidney stones
- Recurrent complicated infection
- Persistent symptoms despite treatment
- Suspected abscess
- Structural urinary abnormalities
-Special / Confirmatory Tests
Urine culture is particularly important in:
- Complicated UTI
- Pregnancy
- Men with suspected UTI
- Recurrent UTI
- Pyelonephritis
- Severe infection
- Treatment failure
Diagnosis
-Diagnosis of uncomplicated lower Urinary Tract Infection (UTI) is often based on:
Typical urinary symptoms + supportive urinalysis.
-Urine culture is used when infection is complicated, recurrent, severe, occurs during pregnancy, or when treatment failure is suspected.
Fever, flank pain, and costovertebral angle tenderness suggest Pyelonephritis.
Management
1. Definitive Treatment
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Appropriate antimicrobial therapy
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Treat underlying urinary obstruction or structural abnormality
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Remove or replace infected urinary devices when appropriate
2. Medical Treatment
Antibiotic choice depends on infection site, patient factors, local resistance patterns, and culture results.
For uncomplicated cystitis, commonly used options include:
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Nitrofurantoin
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Trimethoprim-sulfamethoxazole when appropriate
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Fosfomycin
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Otherlocally appropriate antibiotics
For Pyelonephritis or complicated UTI, treatment may require:
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Fluoroquinolones in appropriate settings
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Cephalosporins
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Other antibiotics based on severity and susceptibility
4. Supportive Management
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Adequate hydration
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Analgesia
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Antipyretics
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Monitor symptoms and urine output when clinically indicated
Complications
- Recurrent Urinary Tract Infection (UTI)
- Pyelonephritis
- Renal abscess
- Perinephric abscess
- Sepsis
- Septic shock
- Acute Kidney Injury (AKI)
- Renal scarring
- Chronic Pyelonephritis
Prognosis
-Most uncomplicated Urinary Tract Infections (UTIs) respond well to appropriate treatment.
–Prognosis is less favorable when infection is complicated by obstruction, stones, resistant organisms, structural abnormalities, or delayed treatment. Recurrent or severe infections can cause renal damage and, rarely, contribute to Chronic Kidney Disease (CKD)
Key Points / Clinical Pearls
- Urinary Tract Infection (UTI) is an infection of any part of the urinary tract.
- Most UTIs are bacterial and result from ascending infection.
- Escherichia coli (E. coli) is the most common causative organism.
- Cystitis primarily causes dysuria, frequency, urgency, and suprapubic discomfort.
- Fever and flank pain suggest Pyelonephritis.
- Urinalysis is an important initial investigation.
- Pyuria and leukocyte esterase commonly support the diagnosis.
- Nitrites may be positive with nitrate-reducing bacteria.
- Urine culture is important in complicated, recurrent, severe, and selected high-risk UTIs.
- Imaging is not routinely required for uncomplicated UTI.
- Antibiotics are the mainstay of treatment.
- Antibiotic selection should consider local resistance patterns and patient factors.
- Infected urinary obstruction requires urgent drainage plus antibiotics.
- European Association of Urology (EAU). EAU Guidelines on Urological Infections .
- Gupta K, Hooton TM, Naber KG, et al. International Clinical Practice Guidelines for the Treatment of Acute Uncomplicated Cystitis and Pyelonephritis in Women: A 2010 Update by the IDSA and ESCMID. Clin Infect Dis. 2011;52(5):e103-e120. Clinical Infectious Diseases .
- Flores-Mireles AL, Walker JN, Caparon M, Hultgren SJ. Urinary Tract Infections: Epidemiology, Mechanisms of Infection and Treatment Options. Nat Rev Microbiol. 2015;13(5):269-284. Nature Reviews Microbiology .
- Medina M, Castillo-Pino E. An Introduction to the Epidemiology and Burden of Urinary Tract Infections. Ther Adv Urol. 2019;11:1756287219832172. Therapeutic Advances in Urology .
- National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). Urinary Tract Infection (UTI) . National Institutes of Health.
- National Library of Medicine (NIH). Urinary Tract Infection . StatPearls.