Pyelonephritis, Acute

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

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

Medications

• 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

Surgery

• Nephrostomy drainage if ureteral obstruction

Therapeutic Procedures

• Failure to respond warrants abdominal imaging to exclude obstruction

• Catheter drainage

Complications

• 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

Prognosis

• With prompt diagnosis and treatment, good prognosis

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

When to Refer

• Evidence of complicating factors (urolithiasis, obstruction)

• Failure to improve clinically in 48 hours

When to Admit

• Severe infections or complicating factors, evidence of sepsis and need for parenteral antibiotics

• Need for radiographic imaging or drainage of urinary tract obstruction