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For further information, see CMDT Part 23-03: Genitourinary Tract Infections

Key Features

Essentials of Diagnosis

  • Fever

  • Flank pain

  • Irritative voiding symptoms

  • Positive urine culture

General Considerations

  • Acute pyelonephritis is an infectious inflammatory disease involving the kidney parenchyma and renal pelvis

  • Most common causative organisms

    • Escherichia coli

    • Proteus

    • Klebsiella

    • Enterobacter

    • Pseudomonas

  • Less common causative organisms

    • Enterococcus faecalis

    • Staphylococcus aureus

Clinical Findings

Symptoms and Signs

  • Fever

  • Flank pain

  • Shaking chills

  • Urgency, frequency, dysuria

  • Nausea, vomiting, diarrhea

  • Tachycardia

  • Costovertebral angle tenderness

Differential Diagnosis

  • Acute cystitis or a lower urinary source

  • Appendicitis

  • Cholecystitis

  • Pancreatitis

  • Diverticulitis

  • Lower lobe pneumonia

  • In males: acute epididymitis and acute prostatitis


Laboratory Tests

  • Complete blood count: leukocytosis and a left shift

  • Urinalysis: pyuria, bacteriuria, hematuria, white blood cell casts

  • Urine (and sometimes blood) cultures: positive

Imaging Studies

  • Renal ultrasound may show hydronephrosis from a stone or other source of obstruction (in complicated cases)

  • CT scan may demonstrate decreased perfusion of the kidney or focal areas within the kidney and nonspecific perinephric fat stranding



  • Inpatients: intravenous ampicillin and an aminoglycoside until afebrile for 24 hours, then oral antibiotics for 3 weeks

  • If local antibiograms demonstrate local resistance rates for the oral regimen exceed 10%, an initial 24-hour intravenous dose of antibiotic is required

  • Outpatients: empiric therapy

    • Ampicillin, 1 g every 6 hours, and gentamicin, 1 mg/kg every 8 hours, intravenously for 14 days

    • Ciprofloxacin, 750 mg every 12 hours orally for 7–14 days

    • Levofloxacin, 750 mg daily orally 5 days

    • Trimethoprim-sulfamethoxazole, 160/800 mg every 12 hours orally for 10–14 days

  • Increasing (up to 20%) resistance of E coli and other organisms causing urinary tract infections has been noted

  • FDA advises restricting fluoroquinolone use for uncomplicated urinary tract infections

  • Randomized trial data suggests that ceftolozane-tazobactam may yield better response rates compared to high-dose levofloxacin in the treatment of pyelonephritis and complicated lower-tract infection


  • Nephrostomy drainage if ureteral obstruction

Therapeutic Procedures

  • Failure to respond warrants abdominal imaging to exclude obstruction

  • Catheter drainage



  • Sepsis with shock

  • In diabetic patients, emphysematous pyelonephritis resulting from gas-producing organisms may be life-threatening if not adequately treated

  • If coexistent kidney disease is present, scarring or chronic pyelonephritis may result

  • Inadequate therapy could result in abscess formation


  • With prompt diagnosis and treatment, good prognosis

  • With complicating factors, underlying renal disease, and increasing patient age, less favorable prognosis


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