• Description: Pyelonephritis is an infection of the kidney or upper urinary tract.

  • Prevalence: More than 200,000 cases per year in the United States. Acute pyelonephritis during pregnancy: 0.5%–2%.

  • Predominant Age: Any.

  • Genetics: No genetic predisposition known.

Etiology and Pathogenesis

  • Causes: Pyelonephritis generally develops when pathogens associated with a bladder infection (most commonly Escherichia coli ) ascend to the kidneys via the ureters. Seeding of the kidneys may also occur from bacteremia or, in uncommon cases, from lymphatic spread.

  • Risk Factors: Bladder infection (acute, chronic, recurrent), pregnancy, urologic abnormalities (nephrolithiasis, strictures, stents, urinary diversions), immunocompromising conditions (neutropenia, advanced human immunodeficiency virus [HIV] infection), poorly controlled diabetes mellitus. Pyelonephritis in pregnancy: Age <20 years, nulliparity, smoking, late presentation to care, sickle cell trait.

Signs and Symptoms

  • Flank pain, costovertebral angle tenderness

  • Fever (>99.9°F [37.7°C]), chills

  • Nausea and vomiting (inconsistent)

  • Symptoms of cystitis

  • Hematuria

Diagnostic Approach

Differential Diagnosis

  • Pelvic inflammatory disease

  • Acute (uncomplicated) cystitis

  • Nephrolithiasis

  • Renal tumors

  • Associated Conditions: Cystitis, septicemia, perinephric abscess

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