Overview
UTI and Pyelonephritis
Quick Reference
Critical Alerts
- Pyelonephritis can progress to urosepsis: Recognize early, treat aggressively
- Complicated UTI needs broader coverage: Catheter, obstruction, male, immunocompromised
- Antibiotic resistance is increasing: Check local antibiogram
- Imaging for suspected obstruction or abscess: CT with contrast if renal function allows
- Admit if cannot tolerate PO, septic, pregnant, or obstruction suspected
- Fluoroquinolone resistance rising: Reserve for appropriate cases
Key Diagnostics
| Test | Finding |
|---|---|
| Urinalysis | Pyuria (>0 WBC/hpf), bacteriuria, positive leukocyte esterase/nitrite |
| Urine culture | ≥10⁵ CFU/mL (or ≥10³ if symptomatic) |
| Blood cultures | If sepsis, pyelonephritis, or complicated UTI |
| CT abdomen/pelvis | For obstruction, abscess, stone vs pyelo |
Classification
| Type | Definition |
|---|---|
| Uncomplicated cystitis | Lower UTI in non-pregnant, premenopausal woman with normal anatomy |
| Complicated UTI | UTI with risk factors (male, catheter, obstruction, pregnancy, diabetes, immunocompromise) |
| Pyelonephritis | Upper UTI involving kidney parenchyma |
| Urosepsis | Sepsis secondary to urinary source |
Emergency Treatments
| Condition | Treatment | Duration |
|---|---|---|
| Uncomplicated cystitis | Nitrofurantoin 100mg BID or TMP-SMX DS BID | 5 days (nitrofurantoin) or 3 days (TMP-SMX) |
| Uncomplicated pyelonephritis | Ciprofloxacin 500mg BID PO or Ceftriaxone 1g IV | 7 days PO or switch to PO after IV improvement |
| Complicated UTI/Pyelonephritis | Ceftriaxone 1-2g IV or Pip-Tazo | 7-14 days (+ source control) |
| Urosepsis | Broad-spectrum IV abx (Pip-Tazo, Meropenem) + fluids | ICU, source control |
Definition
Overview
Urinary tract infections (UTIs) are among the most common bacterial infections. They range from uncomplicated cystitis (lower UTI) to pyelonephritis (upper UTI) and urosepsis. Prompt recognition and appropriate antibiotic therapy are essential. Complicated UTIs and pyelonephritis require more aggressive treatment and often hospitalization.
Classification
By Anatomic Location:
| Type | Definition |
|---|---|
| Cystitis | Infection limited to bladder (lower UTI) |
| Pyelonephritis | Infection of kidney parenchyma (upper UTI) |
| Urethritis | Infection of urethra (often STI-related) |
| Prostatitis | Infection of prostate (in males) |
By Complexity:
| Type | Features |
|---|---|
| Uncomplicated | Non-pregnant, premenopausal woman with normal anatomy |
| Complicated | Male, pregnancy, catheter, obstruction, anatomic abnormality, immunocompromise, diabetes, recent instrumentation |
Epidemiology
- Incidence: 50-60% of women will have ≥1 UTI
- Recurrent UTI: 20-30% of women
- More common in women: Short urethra, proximity to vagina/anus
- Pyelonephritis: 250,000 cases/year in US
Etiology
Common Pathogens (Community-Acquired):
| Organism | Frequency |
|---|---|
| E. coli | 80-90% |
| Klebsiella | 5-10% |
| Proteus | 1-5% |
| Staphylococcus saprophyticus | 5-10% (young women) |
| Enterococcus | 1-5% |
Complicated UTI/Healthcare-Associated:
| Organism | Notes |
|---|---|
| E. coli (resistant strains) | ESBL-producing |
| Pseudomonas | Healthcare-associated |
| Enterococcus | Catheter-associated |
| Candida | Catheter, immunocompromised |
Pathophysiology
Ascending Infection (Most Common)
- Periurethral colonization with fecal flora
- Ascent via urethra to bladder
- Adhesion to bladder epithelium
- Cystitis develops
- Ascent to kidneys → Pyelonephritis
Risk Factors for UTI
| Factor | Mechanism |
|---|---|
| Female sex | Short urethra |
| Sexual activity | Introduces bacteria |
| Catheter | Direct inoculation, biofilm |
| Obstruction (stone, BPH) | Stasis, incomplete emptying |
| Diabetes | Impaired immunity, glucosuria |
| Pregnancy | Ureteral dilation, stasis |
| Immunocompromise | Impaired host defense |
Progression to Pyelonephritis
- Vesicoureteral reflux or ascending infection
- Bacterial invasion of renal parenchyma
- Inflammatory response → Tissue damage
- Bacteremia and sepsis possible
Clinical Presentation
Cystitis Symptoms
| Symptom | Description |
|---|---|
| Dysuria | Pain or burning with urination |
| Frequency | Urinating often |
| Urgency | Sudden need to urinate |
| Suprapubic pain | Lower abdominal discomfort |
| Hematuria | Blood in urine (common) |
| No fever | Typically afebrile |
Pyelonephritis Symptoms
| Symptom | Description |
|---|---|
| Flank pain | Unilateral, costovertebral angle (CVA) tenderness |
| Fever | Often high (>8.5°C) |
| Chills, rigors | Systemic illness |
| Nausea, vomiting | Common |
| Lower UTI symptoms | May or may not be present |
History
Key Questions:
Physical Examination
Cystitis:
Pyelonephritis:
| Finding | Significance |
|---|---|
| CVA tenderness | Classic for pyelonephritis |
| Fever | Systemic infection |
| Tachycardia | May indicate sepsis |
| Hypotension | Urosepsis |
Abdominal Exam:
Dysuria, frequency, urgency
Common presentation.
Flank pain, fever, chills
Common presentation.
Hematuria
Common presentation.
Vaginal discharge (consider STI, vaginitis)
Common presentation.
Prior UTIs and antibiotics used
Common presentation.
Pregnancy
Common presentation.
Catheter or recent instrumentation
Common presentation.
Diabetes, immunocompromise
Common presentation.
Recent antibiotics (resistance risk)
Common presentation.
Red Flags
Concerning for Complicated UTI or Urosepsis
| Finding | Concern | Action |
|---|---|---|
| Hypotension, tachycardia | Urosepsis | IV fluids, broad-spectrum abx, ICU |
| Altered mental status | Sepsis | Aggressive resuscitation |
| Obstructive symptoms (anuria, severe flank pain) | Obstructed pyelonephritis | Emergent imaging, urology for decompression |
| Pregnancy + pyelonephritis | High risk for preterm labor, sepsis | Admit, IV abx |
| Immunocompromised | Atypical organisms, rapid progression | Broad coverage, admit |
| Male UTI | Always complicated; assess prostate | Broader workup |
Differential Diagnosis
Other Causes of Dysuria/Urinary Symptoms
| Diagnosis | Features |
|---|---|
| STI (chlamydia, gonorrhea) | Vaginal/urethral discharge, high-risk sexual history |
| Vaginitis | Vaginal discharge, pruritus, no urinary frequency |
| Urethritis | Dysuria without frequency, discharge |
| Nephrolithiasis | Colicky flank pain, hematuria, no pyuria |
| Interstitial cystitis | Chronic symptoms, sterile cultures |
| Prostatitis | Male, perineal pain, tender prostate |
| Appendicitis (retrocecal) | RLQ pain, may have pyuria |
| Pelvic inflammatory disease | Lower abdominal pain, cervical motion tenderness |
Diagnostic Approach
Urinalysis (UA)
| Finding | Significance |
|---|---|
| Pyuria (>0 WBC/hpf) | Supports UTI; sensitive |
| Bacteriuria | Supports UTI |
| Leukocyte esterase | Positive = WBCs present |
| Nitrite | Positive = Gram-negative bacteria (not all produce nitrite) |
| Hematuria | Common in UTI; also consider stone, malignancy |
Urine Culture
Indications:
- All pyelonephritis
- All complicated UTI
- Treatment failure
- Recurrent UTI
- Pregnancy
Thresholds:
- ≥10⁵ CFU/mL = Classic definition
- ≥10³ CFU/mL with symptoms = Can be significant
Blood Tests
| Test | Indication |
|---|---|
| CBC | Pyelonephritis, sepsis |
| BMP | Renal function, electrolytes |
| Lactate | Sepsis |
| Blood cultures | Pyelonephritis, sepsis, complicated UTI |
Imaging
Not Routinely Needed for Uncomplicated Cystitis
Indications for Imaging:
| Indication | Modality |
|---|---|
| Suspected obstruction | CT abdomen/pelvis without contrast (or ultrasound) |
| Poor response to treatment | CT with contrast |
| Abscess suspected | CT with contrast |
| Male UTI | Ultrasound or CT (to assess prostate, obstruction) |
| Recurrent UTI | Ultrasound or CT (structural abnormality) |
Treatment
Principles of Management
- Classify UTI: Uncomplicated cystitis vs complicated vs pyelonephritis
- Empiric antibiotics: Based on local resistance patterns
- Urine culture: For all pyelonephritis and complicated UTI
- Imaging: If obstruction or abscess suspected
- Admission: For sepsis, unable to tolerate PO, obstruction, pregnancy
Uncomplicated Cystitis
First-Line Antibiotics:
| Agent | Dose | Duration |
|---|---|---|
| Nitrofurantoin monohydrate/macrocrystals | 100 mg PO BID | 5 days |
| TMP-SMX DS | 1 tab PO BID | 3 days |
| Fosfomycin | 3 g PO × 1 dose | Single dose |
Second-Line (If Allergies/Resistance):
| Agent | Dose | Duration |
|---|---|---|
| Ciprofloxacin | 250 mg PO BID | 3 days |
| Levofloxacin | 250 mg PO daily | 3 days |
| Beta-lactams (amox-clav, cephalexin) | 500 mg TID | 5-7 days (less effective) |
Avoid Fluoroquinolones for Uncomplicated Cystitis When Possible: Reserve for more serious infections
Uncomplicated Pyelonephritis (Outpatient)
Criteria for Outpatient Treatment:
- Mild-moderate illness
- Able to tolerate PO fluids and medications
- No vomiting
- Reliable follow-up
Antibiotics:
| Agent | Dose | Duration |
|---|---|---|
| Ciprofloxacin | 500 mg PO BID | 7 days |
| Levofloxacin | 750 mg PO daily | 5 days |
| TMP-SMX DS (if susceptible) | 1 tab PO BID | 14 days |
| Ceftriaxone 1g IV × 1 + PO step-down | 7 days total |
Complicated UTI and Pyelonephritis (Inpatient)
Empiric IV Antibiotics:
| Agent | Dose | Notes |
|---|---|---|
| Ceftriaxone | 1-2 g IV q24h | First-line for many |
| Ciprofloxacin | 400 mg IV q12h | If FQ-susceptible |
| Piperacillin-Tazobactam | 3.375-4.5 g IV q6h | If Pseudomonas risk |
| Meropenem | 1 g IV q8h | If ESBL or severe sepsis |
| Vancomycin | 15-20 mg/kg IV q8-12h | If Enterococcus or MRSA suspected |
Duration: 7-14 days (shorter if source controlled and responding)
Urosepsis
- Fluid resuscitation: 30 mL/kg crystalloids
- Broad-spectrum IV antibiotics: Pip-Tazo, Meropenem, or Ceftriaxone + Vancomycin
- Blood cultures × 2
- Imaging: CT to assess for obstruction or abscess
- Urology consult: For obstructed system → Emergent decompression (nephrostomy or stent)
- ICU admission: If hemodynamically unstable
Obstructed Pyelonephritis (Pyonephrosis)
Medical Emergency:
- Antibiotics + Emergent decompression (percutaneous nephrostomy or ureteral stent)
- Urology consultation STAT
- Delay = High mortality
Catheter-Associated UTI (CAUTI)
- Remove or replace catheter before antibiotic start
- Shorter course (7 days if symptoms resolve quickly)
- Broaden coverage for healthcare-associated organisms
Pregnancy
- All symptomatic UTI and asymptomatic bacteriuria should be treated
- Safe antibiotics: Nitrofurantoin (avoid near term), cephalexin, amoxicillin
- Avoid: Fluoroquinolones, TMP-SMX (1st trimester)
- All pyelonephritis in pregnancy = Admit for IV antibiotics
Disposition
Discharge Criteria (Cystitis)
- Uncomplicated, afebrile
- Able to tolerate PO
- Reliable follow-up
Discharge Criteria (Pyelonephritis)
- Mild-moderate severity
- Afebrile or low-grade fever
- Able to tolerate PO fluids and antibiotics
- No obstruction, abscess, or pregnancy
Admission Criteria
- Sepsis or hemodynamic instability
- Unable to tolerate PO
- Pregnancy + pyelonephritis
- Obstruction (pyonephrosis)
- Abscess
- Immunocompromised with severe illness
- Failed outpatient therapy
Follow-Up
| Situation | Follow-Up |
|---|---|
| Uncomplicated cystitis | PRN if no improvement in 48h |
| Pyelonephritis (outpatient) | 48-72 hours for culture review |
| Recurrent UTI | Urology referral |
| Post-hospitalization | PCP within 1 week |
Patient Education
Condition Explanation
- "You have a bladder/kidney infection caused by bacteria."
- "Antibiotics will clear the infection."
- "Drink plenty of fluids."
- "Complete the full course of antibiotics."
Prevention
- Stay hydrated
- Urinate frequently; don't hold urine
- Wipe front to back
- Urinate after sexual intercourse
- Avoid irritants (douching, spermicides)
- Cranberry products: Limited evidence, but low risk
When to Return
- Fever, chills, or worsening flank pain
- Unable to keep down fluids or medications
- Symptoms not improving after 48 hours
- Blood in urine or decreased urine output
Special Populations
Elderly
- Atypical presentation (confusion, falls)
- Avoid treating asymptomatic bacteriuria (common in elderly)
- Lower threshold for imaging and admission
Pregnancy
- All symptomatic UTI and asymptomatic bacteriuria require treatment
- Pyelonephritis = Admit
- Avoid fluoroquinolones and TMP-SMX (1st trimester)
Men
- All UTIs in men are complicated
- Consider prostatitis
- Longer treatment duration (7-14 days)
- Urology referral for recurrence
Catheterized Patients
- Remove or replace catheter
- Treat only if symptomatic
- Asymptomatic bacteriuria common and should NOT be treated
Immunocompromised
- Broader empiric coverage
- Lower threshold for admission
- Consider atypical organisms
Quality Metrics
Performance Indicators
| Metric | Target | Rationale |
|---|---|---|
| Urine culture obtained before antibiotics (complicated/pyelo) | >0% | Guide therapy |
| Avoid FQs for uncomplicated cystitis | >0% | Stewardship |
| Imaging for suspected obstruction | 100% | Identify emergency |
| Pregnancy + pyelo admitted | 100% | High-risk population |
| Appropriate antibiotic duration | >0% | Avoid resistance |
Documentation Requirements
- Symptoms and duration
- Urinalysis results
- Urine culture ordered (if indicated)
- Antibiotic choice and rationale
- Disposition and follow-up plan
Key Clinical Pearls
Diagnostic Pearls
- Pyuria without bacteriuria: Consider STI, interstitial cystitis, or partially treated UTI
- Nitrite-negative does not rule out UTI: Not all bacteria produce nitrite (Enterococcus, Staph)
- Elderly confusion + pyuria ≠ UTI: Avoid treating asymptomatic bacteriuria
- Flank pain + fever = pyelonephritis: Even without lower UTI symptoms
- Order culture for all pyelonephritis and complicated UTI: Guides therapy
Treatment Pearls
- Nitrofurantoin for cystitis, NOT pyelonephritis: Doesn't achieve renal tissue levels
- FQs reserved for pyelonephritis or resistance: Stewardship
- Obstructed pyelo = nephrostomy or stent: Antibiotics alone won't work
- Remove or replace catheter before treating CAUTI: Biofilm issue
- 7 days is often enough for uncomplicated pyelonephritis: If responding
Disposition Pearls
- Sepsis, pregnancy, obstruction = Admit: Non-negotiable
- Outpatient pyelonephritis possible: If mild and can tolerate PO
- Follow up culture results: Adjust antibiotics as needed
- Recurrent UTI needs workup: Imaging, urology referral
References
- Gupta K, et al. International Clinical Practice Guidelines for the Treatment of Acute Uncomplicated Cystitis and Pyelonephritis in Women. Clin Infect Dis. 2011;52(5):e103-e120.
- Nicolle LE, et al. Clinical Practice Guideline for the Management of Asymptomatic Bacteriuria: 2019 Update by IDSA. Clin Infect Dis. 2019;68(10):e83-e110.
- Hooton TM. Uncomplicated Urinary Tract Infection. N Engl J Med. 2012;366(11):1028-1037.
- Foxman B. Epidemiology of urinary tract infections: Incidence, morbidity, and economic costs. Am J Med. 2002;113(1A):5S-13S.
- Wagenlehner FM, et al. Diagnosis and management for urosepsis. Int J Urol. 2013;20(10):963-970.
- Colgan R, et al. Diagnosis and treatment of acute pyelonephritis in women. Am Fam Physician. 2011;84(5):519-526.
- ACOG Committee Opinion No. 797. Treatment of urinary tract infections in nonpregnant women. Obstet Gynecol. 2020;135(1):e52-e60.
- UpToDate. Acute uncomplicated cystitis in women. 2024.