Renal abscess

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Background

Renal anatomy.
Perinephric space with exaggerated pararenal space to show retroperitoneal structures. Perinephric bridging septa are seen between the left kidney and the adjacent renal fascia.
  • Rare clinical entity which can lead to delayed diagnosis
  • Usually a complication of a UTI or pyelonephritis
  • Less often can be due to hematogenous spread from other sources of infection

Risk Factors

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

Genitourinary infection

(1) Human urinary system: (2) kidney; (3) renal pelvis; (4) ureter; (5) urinary bladder (6) urethra.
Additional structures: (7) adrenal gland; (8) renal artery and vein; (9) inferior vena cava; (10) abdominal aorta; (11) common iliac artery and vein; (12) liver; (13) large intestine; (14) pelvis.

"UTI" frequently refers specifically to acute cystitis, but may also be used as a general term for all urinary infections; use location-specific diagnosis.

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

Complications

Differential Diagnosis

Evaluation

CT showing a right renal abscess that has burst into the perinephric space (arrow), best appreciated as the soft tissue density interposed between the kidney and adjacent liver

.

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

Management

  • Antibiotics
  • 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


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