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

Perinephric vs renal abscess

	Perinephric	Renal
Necrotic Area	perinephric fat between the renal cortex and Gerota's fascia	renal parenchyma
Cause	Pyelonephritis (majority)	Pyelonephritis (vast majority)
Risk of morbidity	Higher	Lower

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

Evaluation

• 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
      • Vancomycin 15-20mg/kg IV
• Percutaneous drainage
• Open surgical management if patient 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.
• 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

Authors

Ashley Phipps, Ross Donaldson, Neil Young, Daniel Ostermayer