Urinary Tract Infections

Urinary Tract Infections

Urinary Tract Infections

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UTI Basics - Pee Problem Primer

Kidney Anatomy with Renal Artery, Vein, and Ureter

  • Definition: Microbial infection anywhere along the urinary tract.
  • Epidemiology: Females > males; common in young women, elderly.
  • Risk Factors: 📌 Sexual activity, Catheterization, Obstruction, Diabetes, Immunosuppression, Pregnancy.
  • Classification:
    • Site: Upper (pyelonephritis) vs Lower (cystitis, urethritis).
    • Complexity: Uncomplicated (healthy female) vs Complicated (e.g., male, catheter, obstruction).
    • Pattern: Recurrent UTI (≥2 in 6 months or ≥3 in 1 year); Relapse vs Reinfection.

⭐ Most common cause of uncomplicated UTI is E. coli.

Bugs & Routes - Microbe Mayhem March

  • Common Pathogens & Key Associations:
    • E. coli: ~80%
    • Staphylococcus saprophyticus: Key in young women.

      Staphylococcus saprophyticus is a common cause of UTI in sexually active young women, often called 'honeymoon cystitis'.

    • Klebsiella
    • Proteus: Struvite stones, alkaline urine; Urease: $Urea + H₂O \rightarrow 2NH₃ + CO₂$
    • Enterococcus
    • Pseudomonas: Catheter, hospital-acquired
  • 📌 KEEPS Mnemonic: Klebsiella, E. coli, Enterococcus/Enterobacter, Proteus/Pseudomonas, S. saprophyticus.
  • Routes of Infection:
    • Ascending (most common)
    • Hematogenous, Lymphatic (both rare)
  • Virulence Factors:
    • Pili/fimbriae (adhesion)
    • Hemolysin
    • Urease (Proteus) UTI Pathogenesis: Bacterial Adherence and Invasion

Signs & Sleuthing - Symptom Spotter's Guide

  • Clinical Features:
    FeatureCystitisPyelonephritis
    SymptomsDysuria, frequency, urgency, suprapubic pain, hematuriaFever, chills, flank pain, CVA tenderness, N/V, +/- cystitis sx
  • Atypical: Elderly (confusion), Children (fever).
  • Urinalysis:
    • Dipstick: Leukocyte esterase (LE), Nitrites.

    ⭐ Presence of nitrites on urine dipstick is highly specific for Enterobacteriaceae infection.

    • Microscopy: Pyuria (>10 WBCs/hpf), Bacteriuria, RBCs, WBC casts (pyelonephritis). WBC cast in urine microscopy
  • Urine Culture:
    • Indications: Complicated UTI, pyelonephritis, recurrent UTI, treatment failure, pregnancy.
    • Significant Bacteriuria: ≥10⁵ CFU/mL (midstream); ≥10² CFU/mL (symptomatic women/catheter).

Treatment Tactics - Bug Battle Blueprint

  • General Measures: ↑Hydration, regular voiding.
  • Uncomplicated Cystitis (Outpatient):
    • Nitrofurantoin 100mg BD x 5 days
    • TMP-SMX DS BD x 3 days
    • Fosfomycin 3g single dose
    • Avoid fluoroquinolones if alternatives exist.
  • Complicated UTI / Pyelonephritis:
    • Longer course, broader spectrum (e.g., Fluoroquinolones, 3rd gen Cephalosporins, Aminoglycosides).
    • IV for severe cases. Tailor to culture results.
  • Pain Relief: Phenazopyridine.

⭐ Nitrofurantoin is a first-line agent for uncomplicated cystitis but should be avoided if GFR < 30-60 mL/min or in suspected pyelonephritis.

Special Cases - Tricky Tract Troubles

  • UTI in Pregnancy: Screen & treat ASB. Risks: pyelo, preterm. Safe: Cephalexin, Nitrofurantoin (not term), Amoxicillin. Avoid: FQ, Tetracyclines, TMP-SMX (1st/3rd).

    ⭐ ASB in pregnancy: screen & treat to prevent pyelonephritis, preterm birth.

  • CAUTI: Nosocomial. Dx: symptoms + ≥10³ CFU/mL (catheter). Mgmt: change catheter, treat symptomatic.
  • ASB: ≥10⁵ CFU/mL, no symptoms. Treat if:
    • Pregnant
    • Pre-urologic procedure (mucosal bleed)
  • Prostatitis: Linked to recurrent UTI in men.

Prevention & Pitfalls - Defense & Dangers

  • Recurrent UTI Prevention:
    • Behavioral: Post-coital voiding, adequate hydration.
    • Antimicrobial prophylaxis: Continuous low-dose, post-coital.
    • Non-antimicrobial: Cranberry (limited evidence), topical estrogen (postmenopausal), D-mannose.
  • Complications (Dangers):
    • Pyelonephritis, renal/perinephric abscess.
    • Papillary necrosis, sepsis/urosepsis.
    • Chronic pyelonephritis, renal scarring.
    • Xanthogranulomatous pyelonephritis.

⭐ Emphysematous pyelonephritis: a life-threatening necrotizing infection with gas in renal tissues, predominantly affecting diabetic patients.

High‑Yield Points - ⚡ Biggest Takeaways

  • E. coli is the leading uropathogen in most UTIs.
  • Significant bacteriuria is >10^5 CFU/mL; pyuria is crucial for diagnosis.
  • Nitrofurantoin, TMP-SMX, and Fosfomycin are first-line for uncomplicated cystitis.
  • Complicated UTIs (e.g., males, pregnancy, catheters) need broader/longer antibiotic courses.
  • Treat asymptomatic bacteriuria mainly in pregnancy and pre-urologic procedures.
  • Sterile pyuria may indicate urogenital TB or Chlamydia.
  • CAUTI is the most common hospital-acquired infection; prioritize prevention.

Practice Questions: Urinary Tract Infections

Test your understanding with these related questions

Which one of the following gram-positive organisms is the most common cause of UTI among sexually active women?

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Flashcards: Urinary Tract Infections

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_____ is the treatment of choice for proximal ureteral stones of diameter >10 mm

TAP TO REVEAL ANSWER

_____ is the treatment of choice for proximal ureteral stones of diameter >10 mm

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