## Clinical Presentation & Diagnosis This patient has **acute pyelonephritis with sepsis** (fever, flank pain, CVA tenderness, pyuria, WBC casts, elevated creatinine, hypotension). Risk factors include diabetes mellitus and male gender. **Key Point:** Acute pyelonephritis is a systemic infection of the kidney parenchyma and collecting system. In community-acquired disease, E. coli accounts for 80–90% of cases, followed by Klebsiella, Proteus, and other Enterobacteriaceae. ## Organism Identification | Organism | Prevalence in UTI | Clinical Context | Key Features | |----------|-------------------|------------------|---------------| | **E. coli** | 80–90% (community pyelonephritis) | Most common; ascending infection from bladder | Gram-negative rod; ferments lactose; produces nitrites | | Klebsiella | 5–10% | Often nosocomial or in diabetics | Gram-negative rod; mucoid colonies; non-motile | | Proteus | 3–5% | Urease-positive; staghorn calculi risk | Gram-negative rod; swarming motility | | Pseudomonas | <1% (community); up to 20% (nosocomial) | Catheterized, immunocompromised, hospital-acquired | Gram-negative rod; oxidase-positive; aerobic | | Staph. saprophyticus | 5–15% (uncomplicated cystitis in young women) | Young, non-pregnant women; NOT pyelonephritis | Gram-positive cocci; catalase-positive | **High-Yield:** S. saprophyticus is a cause of **uncomplicated cystitis** in young women, NOT pyelonephritis in a 52-year-old man. ## Management Algorithm ```mermaid flowchart TD A[Acute pyelonephritis + sepsis]:::outcome --> B[Blood cultures + urine culture]:::action B --> C{Hemodynamically stable?}:::decision C -->|No| D[IV antibiotics + fluid resuscitation]:::action C -->|Yes| E[IV antibiotics + monitor]:::action D --> F[Empiric broad-spectrum coverage]:::action E --> F F --> G[Ceftriaxone 1-2 g IV q12h OR Cefotaxime]:::action G --> H[De-escalate after culture results]:::action H --> I[Switch to oral agent after defervescence]:::outcome ``` ## Empiric Antibiotic Choice **Key Point:** In community-acquired acute pyelonephritis with sepsis, empiric therapy should cover E. coli and other Enterobacteriaceae pending culture results. **Recommended empiric regimen:** - **Ceftriaxone 1–2 g IV every 12 hours** (or cefotaxime) - OR fluoroquinolone (levofloxacin 750 mg IV daily) if beta-lactam allergy - Continue until afebrile ≥24 hours, then switch to oral fluoroquinolone or trimethoprim-sulfamethoxazole for 14–21 days total **Clinical Pearl:** This patient is hypotensive (100/65) and has elevated creatinine—signs of sepsis. IV antibiotics are mandatory; oral monotherapy is inappropriate. **Warning:** Fluoroquinolone monotherapy is suboptimal for sepsis; cephalosporin or aminoglycoside-containing regimens are preferred for empiric coverage in hospitalized patients with systemic toxicity. ## Why Pseudomonas Is Not First-Line Pseudomonas aeruginosa is a nosocomial pathogen; community-acquired pyelonephritis is almost never caused by Pseudomonas unless there is prior instrumentation, catheterization, or recent hospitalization—none of which this patient has. [cite:Harrison 21e Ch 304; Robbins & Cotran 10e Ch 20]
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