Renal abscess

Background

• Rare clinical entity which can lead to delayed diagnosis
• Usually a complication of a UTI or pyelonephritis
  • Most commonly due to E. Coli, Klebsiella, Proteus
• Less often can be due to hematogenous spread from other sources of infection
  • Most commonly due to Staph aureus

Risk Factors

• Inadequately treated or delayed treatment of UTI or pyelonephritis
• Diabetes
• Renal calculi
• Ureteral obstruction
• Any underlying urinary tract abnormality
• Immunosuppression

Clinical Features

• Costovertebral, flank, lumbar, lower chest, or back pain
  • Usually unilateral
• Fever, especially if prolonged or after antibiotic initiation
• Nausea, vomiting
• UTI or pyelonephritis symptoms not improving with antibiotics

Differential Diagnosis

• UTI
• Pyelonephritis
• Renal cyst
• Renal cancer

Diagnosis

• Labs
  • CBC, BMP, UA, lactate
  • Urine culture, blood cultures
    • Some studies have shown up to 66% will have + blood cultures
• Imaging
  • US
    • Well-defined hypoechoic lesion with thick walls and usually with internal debris
  • CT

Management

• Antibiotics
  • Broad spectrum if unclear source
    • If urinary source cover typical urinary pathogens
      • Ceftriaxone 1g IV
      • Piperacillin-Tazobactam 4.5 g IV
    • If hematogenous spread considered, cover for MSSA and MRSA
      • Vancomycin15-20 mg/kg IV
• Percutaneous drainage
• Open surgical management if pt fails antibiotics/percutaneous drainage

Disposition

• Admission for IV antibiotics and drainage
  • Especially if elderly or elevated BUN or creatinine

Complications

• Need for open surgical management or nephrectomy
• Renal failure
• Sepsis, bacteremia
• Emphysematous kidney
• Cortical abscesses can rupture and form perinephric abscesses

References

• Dembry LM, Andriole VT. “Renal and Perirenal Abscesses” Infectious Disease Clinics North America: 11, 3, (Sept 1997).
• Getting GK, Shaikh N. “Renal Abscess” Journal of EM: 31, 1 (2006): 99-100.
• Tintinalli Judith E, Stapczynski J. Stephan. "Urinary Tract Infections” Tintinalli's Emergency Medicine: A Comprehensive Study Guide. 7th ed. New York: McGraw-Hill, 2011. 632.
• Yen DHT, et al. “Renal Abscess: Early Diagnosis and Treatment” Am J EM: 17, 2 (March 1999).
• Shu T, Green JM, Orihuela E. “Renal and Perirenal Abscesses in Patients with Otherwise Anatomically Normal Urinary Tracts” Journal of Urology: 172 (July 2004): 148-150.
• http://www.ncbi.nlm.nih.gov/pubmed/16798166