II. Definitions

  1. Perinephric Abscess (Perirenal Abscess)
    1. Abscess located outside the renal capsule, but within Gerota's space and fascia
    2. May extend to involve the psoas Muscles, peritoneum and Pelvis
  2. Renal abscess
    1. Abscess within the renal parenchyma

III. Causes

  1. Most Common
    1. Urinary Tract Infection Complication (75%)
      1. Escherichia coli
      2. KlebsiellaPneumoniae
    2. Staphylococcal Aureus Bacteremia
      1. Hematogenous spread
      2. In the pre-antibiotic era, was the most common cause of Perinephric Abscess
      3. Less common source in developed countries
  2. Renal Trauma
  3. Regional contiguous infection spread
    1. Crohn's Disease
    2. Acute Cholecystitis
    3. Acute Appendicitis with rupture appendix
    4. Pelvic Inflammatory Disease

IV. Risk Factors

  1. Diabetes Mellitus
  2. Pregnancy
  3. Urinary Tract Infection
  4. Nephrolithiasis or Ureterolithiasis (found in 20% of cases)
  5. Vesicoureteral reflux
  6. Neurogenic Bladder
  7. Polycystic Kidney Disease

V. Symptoms

  1. Fever (75%) and chills
    1. Fever often persists despite UTI infection management >4-5 days
  2. Flank Pain
  3. Abdominal Pain
    1. Pain may be referred to inguinal region
  4. Frequently absent are Urinary Tract Infection symptoms

VI. Signs

  1. Costovertebral Angle Tenderness (CVA Tenderness)
    1. Present in 75% of patients

VII. Labs

  1. Complete Blood Count
  2. Basic chemistry panel (e.g. chem8)
  3. Urinalysis
    1. Normal urine does NOT exclude Perinephric Abscess
    2. Abscess may not communicate with collecting system
  4. Urine Culture
  5. Blood Cultures
  6. Consider ESR, C-RP

VIII. Imaging

  1. CT Abdomen and Pelvis with contrast (preferred)
    1. Identifies abscess and contiguous involvement
    2. Excludes concurrent Ureterolithiasis

IX. Management

  1. Antibiotics for 14-21 days
    1. Gram Negative Bacteria (most common in developed countries)
      1. See Acute Pyelonephritis
      2. Initial antibiotics cover both urinary tract source and Staphylococcus aureus
    2. Staphylococcal Bacteremia (hematogenous seeding, less common)
      1. Coverage for MRSA with Vancomycin as indicated
      2. Standard MSSA coverage otherwise (e.g. Cefazolin, Nafcillin)
  2. Drainage
    1. Indicated in Perinephric Abscess >3 cm
      1. Drainage per local expert opinion for abscesses <3 cm (versus antibiotics alone)
    2. Technique
      1. Percutaneous catheter (preferred)
      2. Surgical drainage (Urology)

X. Prognosis

  1. Worse outcomes with Diabetes Mellitus, large abscess, advanced age, Renal Insufficiency

XI. Complications

  1. Septic Shock
  2. Fistula formation (e.g. Small Bowel)
  3. Renal Hemorrhage
  4. Contiguous spread (e.g. Pneumonia, peritoneal spread)

XII. References

  1. Lee (2008) Korean J Intern Med 23(3): 140-8
  2. Okafor (2019) Perinephric Abscess, StatPearls, NLM
    1. https://www.ncbi.nlm.nih.gov/books/NBK536936/
  3. (2019) Sanford Guide, accessed on IOS, 10/11/2019

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